ICD 10 Classification of Mental and Behavioral Disorders PDF

The ICD-10 Classification of Mental and Behavioural Disorders Clinical descriptions and diagnostic guidelines World Health Organization -1- Preface In the early 1960s, the Mental Health Programme of the World Health Organization (WHO) became actively engaged in a programme aiming to improve the diagnosis and classification of mental disorders. At that time, WHO convened a series of meetings to review knowledge, actively involving representatives of different disciplines, various schools of thought in psychiatry, and all parts of the world in the programme. It stimulated and conducted research on criteria for classification and for reliability of diagnosis, and produced and promulgated procedures for joint rating of videotaped interviews and other useful research methods. Numerous proposals to improve the classification of mental disorders resulted from the extensive consultation process, and these were used in drafting the Eighth Revision of the International Classification of Diseases (ICD-8). A glossary defining each category of mental disorder in ICD-8 was also developed. The programme activities also resulted in the establishment of a network of individuals and centres who continued to work on issues related to the improvement of psychiatric classification (1, 2). The 1970s saw further growth of interest in improving psychiatric classification worldwide. Expansion of international contacts, the undertaking of several international collaborative studies, and the availability of new treatments all contributed to this trend. Several national psychiatric bodies encouraged the development of specific criteria for classification in order to improve diagnostic reliability. In particular, the American Psychiatric Association developed and promulgated its Third Revision of the Diagnostic and Statistical Manual, which incorporated operational criteria into its classification system. In 1978, WHO entered into a long-term collaborative project with the Alcohol, Drug Abuse and Mental Health Administration (ADAMHA) in the USA, aiming to facilitate further improvements in the classification and diagnosis of mental disorders, and alcohol- and drug-related problems (3). A series of workshops brought together scientists from a number of different psychiatric traditions and cultures, reviewed knowledge in specified areas, and developed recommendations for future research. A major international conference on classification and diagnosis was held in Copenhagen, Denmark, in 1982 to review the recommendations that emerged from these workshops and to outline a research agenda and guidelines for future work (4). Several major research efforts were undertaken to implement the recommendations of the Copenhagen conference. One of them, involving centres in 17 countries, had as its aim the development of the Composite International Diagnostic Interview, an instrument suitable for conducting epidemiological studies of mental disorders in general population groups in different countries (5). Another major project focused on developing an assessment instrument suitable for use by clinicians (Schedules for Clinical Assessment in Neuropsychiatry) (6). Still another study was initiated to develop an instrument for the assessment of personality disorders in different countries (the International Personality Disorder Examination) (7). In addition, several lexicons have been, or are being, prepared to provide clear definitions of terms (8). A mutually beneficial relationship evolved between these projects and the work on definitions of mental and behavioural disorders in the Tenth Revision of the International Classification of Diseases and Related Health Problems -2- (ICD-10) (9). Converting diagnostic criteria into diagnostic algorithms incorporated in the assessment instruments was useful in uncovering inconsistencies, ambiguities and overlap and allowing their removal. The work on refining the ICD-10 also helped to shape the assessment instruments. The final result was a clear set of criteria for ICD-10 and assessment instruments which can produce data necessary for the classification of disorders according to the criteria included in Chapter V(F) of ICD-10. The Copenhagen conference also recommended that the viewpoints of the different psychiatric traditions be presented in publications describing the origins of the classification in the ICD-10. This resulted in several major publications, including a volume that contains a series of presentations highlighting the origins of classification in contemporary psychiatry (10). The preparation and publication of this work, Clinical descriptions and diagnostic guidelines, are the culmination of the efforts of numerous people who have contributed to it over many years. The work has gone through several major drafts, each prepared after extensive consultation with panels of experts, national and international psychiatric societies, and individual consultants. The draft in use in 1987 was the basis of field trials conducted in some 40 countries, which constituted the largest ever research effort of this type designed to improve psychiatric diagnosis (11, 12). The results of the trials were used in finalizing these guidelines. This work is the first of a series of publications developed from Chapter V(F) of ICD-10. Other texts will include diagnostic criteria for researchers, a version for use by general health care workers, a multiaxial presentation, and "crosswalks" - allowing cross- reference between corresponding terms in ICD-10, ICD-9 and ICD-8. Use of this publication is described in the Introduction, and a subsequent section of the book provides notes on some of the frequently discussed difficulties of classification. The Acknowledgements section is of particular significance since it bears witness to the vast number of individual experts and institutions, all over the world, who actively participated in the production of the classification and the guidelines. All the major traditions and schools of psychiatry are represented, which gives this work its uniquely international character. The classification and the guidelines were produced and tested in many languages; it is hoped that the arduous process of ensuring equivalence of translations has resulted in improvements in the clarity, simplicity and logical structure of the texts in English and in other languages. A classification is a way of seeing the world at a point in time. There is no doubt that scientific progress and experience with the use of these guidelines will ultimately require their revision and updating. I hope that such revisions will be the product of the same cordial and productive worldwide scientific collaboration as that which has produced the current text. Norman Sartorius Director, Division of Mental Health World Health Organization References -3- 1.Kramer, M. et al. The ICD-9 classification of mental disorders: a review of its developments and contents. Acta psychiatrica scandinavica, 59:241-262 (1979). 2.Sartorius, N. Classification: an international perspective. Psychiatric annals, 6: 22-35 (1976). 3.Jablensky, A. et al. Diagnosis and classification of mental disorders and alcohol- and drug-related problems: a research agenda for the 1980s. Psychological medicine, 13:907-921 (1983). 4.Mental disorders, alcohol- and drug-related problems: international perspectives on their diagnosis and classification. Amsterdam, Excerpta Medica, 1985 (International Congress Series, No. 669). 5.Robins, L. et al. The composite international diagnostic interview. Archives of general psychiatry, 45: 1069-1077 (1989). 6.Wing, J.K. et al. SCAN: schedules for clinical assessment in neuropsychiatry. Archives of general psychiatry, 47: 589-593 (1990). 7.Loranger, A.W. et al. The WHO/ADAMHA international pilot study of personality disorders: background and purpose. Journal of personality disorders, 5(3): 296-306 (1991). 8.Lexicon of psychiatric and mental health terms. Vol. 1. Geneva, World Health Organization, 1989. 9.International Statistical Classification of Diseases and Related Health Problems. Tenth Revision. Vol. 1: Tabular list, 1992. Vol. 2: Instruction Manual, 1993. Vol. 3: Index (in press). Geneva, World Health Organization. 10.Sartorius, N. et al. (ed.) Sources and traditions in classification in psychiatry. Toronto, Hogrefe and Huber, 1990. 11.Sartorius, N. et al. (ed.) Psychiatric classification in an international perspective. British journal of psychiatry, 152 (Suppl. 1) (1988). 12.Sartorius, N. et al. Progress towards achieving a common language in psychiatry: results from the field trials of the clinical guidelines accompanying the WHO Classification of Mental and Behavioural Disorders in ICD-10. Archives of general psychiatry, 1993, 50:115-124. -4- Acknowledgements Many individuals and organizations have contributed to the production of the classification of mental and behavioural disorders in ICD-10 and to the development of the texts that accompany it. The field trials of the ICD-10 proposals, for example, involved researchers and clinicians in some 40 countries; it is clearly impossible to present a complete list of all those who participated in this effort. What follows is a mention of individuals and agencies whose contributions were central to the creation of the documents composing the ICD-10 family of classifications and guidelines. The individuals who produced the initial drafts of the classification and guidelines are included in the list of principal investigators on pages 312-325: their names are marked by an asterisk. Dr A. Jablensky, then Senior Medical Officer in the Division of Mental Health of WHO, in Geneva, coordinated this part of the programme and thus made a major contribution to the proposals. Once the proposals for the classification were assembled and circulated for comment to WHO expert panels and many other individuals, including those listed below, an amended version of the classification was produced for field tests. These were conducted according to a protocol produced by WHO staff with the help of Dr J. Burke, Dr J.E. Cooper, and Dr J. Mezzich and involved a large number of centres, whose work was coordinated by Field Trial Coordinating Centres (FTCCs). The FTCCs (listed on pages xi-xii) also undertook the task of producing equivalent translations of the ICD in the languages used in their countries. Dr N. Sartorius had overall responsibility for the work on the classification of mental and behavioural disorders in ICD-10 and for the production of accompanying documents. Throughout the phase of field testing and subsequently, Dr J.E. Cooper acted as chief consultant to the project and provided invaluable guidance and help to the WHO coordinating team. Among the team members were Dr J. van Drimmelen, who has worked with WHO from the beginning of the process of developing ICD-10 proposals, and Mrs J. Wilson, who conscientiously and efficiently handled the innumerable administrative tasks linked to the field tests and other activities related to the projects. Mr A. L'Hours provided generous support, ensuring compliance between the ICD-10 development in general and the production of this classification, and Mr G. Gemert produced the index. A number of other consultants, including in particular Dr A. Bertelsen, Dr H. Dilling, Dr J. López-Ibor, Dr C. Pull, Dr D. Regier, Dr M. Rutter and Dr N. Wig, were also closely involved in this work, functioning not only as heads of FTCCs for the field trials but also providing advice and guidance about issues in their area of expertise and relevant to the psychiatric traditions of the groups of countries about which they were particularly knowledgeable. Among the agencies whose help was of vital importance were the Alcohol, Drug Abuse and Mental Health Administration in the USA, which provided generous support to the activities preparatory to the drafting of ICD-10, and which ensured effective and productive consultation between groups working on ICD-10 and those working on the fourth revision of the American Psychiatric Association's Diagnostic and Statistical Manual (DSM-IV) classification; the WHO Advisory Committee on ICD-10, chaired by Dr E. Strömgren; and the World Psychiatric Association which, through its President, Dr -5- C. Stefanis, and the special committee on classification, assembled comments of numerous psychiatrists in its member associations and gave most valuable advice during both the field trials and the finalization of the proposals. Other nongovernmental organizations in official and working relations with WHO, including the World Federation for Mental Health, the World Association for Psychosocial Rehabilitation, the World Association of Social Psychiatry, the World Federation of Neurology, and the International Union of Psychological Societies, helped in many ways, as did the WHO Collaborating Centres for Research and Training in Mental Health, located in some 40 countries. Governments of WHO Member States, including in particular Belgium, Germany, the Netherlands, Spain and the USA, also provided direct support to the process of developing the classification of mental and behavioural disorders, both through their designated contributions to WHO and through contributions and financial support to the centres that participated in this work. The ICD-10 proposals are thus a product of collaboration, in the true sense of the word, between very many individuals and agencies in numerous countries. They were produced in the hope that they will serve as a strong support to the work of the many who are concerned with caring for the mentally ill and their families, worldwide. No classification is ever perfect: further improvements and simplifications should become possible with increases in our knowledge and as experience with the classification accumulates. The task of collecting and digesting comments and results of tests of the classification will remain largely on the shoulders of the centres that collaborated with WHO in the development of the classification. Their addresses are listed below because it is hoped that they will continue to be involved in the improvement of the WHO classifications and associated materials in the future and to assist the Organization in this work as generously as they have so far. Numerous publications have arisen from Field Trial Centres describing results of their studies in connection with ICD-10. A full list of these publications and reprints of the articles can be obtained from Division of Mental Health, World Health Organization, 1211 Geneva 27, Switzerland. Field Trial Coordinating Centres and Directors Dr A. Bertelsen, Institute of Psychiatric Demography, Psychiatric Hospital, University of Aarhus, Risskov, Denmark Dr D. Caetano, Department of Psychiatry, State University of Campinas, Campinas, Brazil Dr S. Channabasavanna, National Institute of Mental Health and Neurosciences, Bangalore, India Dr H. Dilling, Psychiatric Clinic of the Medical School, Lübeck, Germany Dr M. Gelder, Department of Psychiatry, Oxford University Hospital, Warneford Hospital, Headington, England -6- Dr D. Kemali, University of Naples, First Faculty of Medicine and Surgery, Institute of Medical Psychology and Psychiatry, Naples, Italy Dr J.J. López-Ibor Jr, López-Ibor Clinic, Pierto de Hierro, Madrid, Spain Dr G. Mellsop, The Wellington Clinical School, Wellington Hospital, Wellington, New Zealand Dr Y. Nakane, Department of Neuropsychiatry, Nagasaki University, School of Medicine, Nagasaki, Japan Dr A. Okasha, Department of Psychiatry, Ain-Shams University, Cairo, Egypt Dr C. Pull, Department of Neuropsychiatry, Centre Hospitalier de Luxembourg, Luxembourg, Luxembourg Dr D. Regier, Director, Division of Clinical Research, National Institute of Mental Health, Rockville, MD, USA Dr S. Tzirkin, All Union Research Centre of Mental Health, Institute of Psychiatry, Academy of Medical Sciences, Moscow, Russian Federation Dr Xu Tao-Yuan, Department of Psychiatry, Shanghai Psychiatric Hospital, Shanghai, China Former directors of field trial centres Dr J.E. Cooper, Department of Psychiatry, Queen's Medical Centre, Nottingham, England Dr R. Takahashi, Department of Psychiatry, Tokyo Medical and Dental University, Tokyo, Japan Dr N. Wig, Regional Adviser for Mental Health, World Health Organization, Regional Office for the Eastern Mediterranean, Alexandria, Egypt Dr Yang De-sen, Hunan Medical College, Changsha, Hunan, China -7- Introduction Chapter V, Mental and behavioural disorders, of ICD-10 is to be available in several different versions for different purposes. This version, Clinical descriptions and diagnostic guidelines, is intended for general clinical, educational and service use. Diagnostic criteria for research has been produced for research purposes and is designed to be used in conjunction with this book. The much shorter glossary provided by Chapter V(F) for ICD-10 itself is suitable for use by coders or clerical workers, and also serves as a reference point for compatibility with other classifications; it is not recommended for use by mental health professionals. Shorter and simpler versions of the classifications for use by primary health care workers are now in preparation, as is a multiaxial scheme. Clinical descriptions and diagnostic guidelines has been the starting point for the development of the different versions, and the utmost care has been taken to avoid problems of incompatibility between them. Layout It is important that users study this general introduction, and also read carefully the additional introductory and explanatory texts at the beginning of several of the individual categories. This is particularly important for F23.-(Acute and transient psychotic disorders), and for the block F30-F39 (Mood [affective] disorders). Because of the long-standing and notoriously difficult problems associated with the description and classification of these disorders, special care has been taken to explain how the classification has been approached. For each disorder, a description is provided of the main clinical features, and also of any important but less specific associated features. "Diagnostic guidelines" are then provided in most cases, indicating the number and balance of symptoms usually required before a confident diagnosis can be made. The guidelines are worded so that a degree of flexibility is retained for diagnostic decisions in clinical work, particularly in the situation where provisional diagnosis may have to be made before the clinical picture is entirely clear or information is complete. To avoid repetition, clinical descriptions and some general diagnostic guidelines are provided for certain groups of disorders, in addition to those that relate only to individual disorders. When the requirements laid down in the diagnostic guidelines are clearly fulfilled, the diagnosis can be regarded as "confident". When the requirements are only partially fulfilled, it is nevertheless useful to record a diagnosis for most purposes. It is then for the diagnostician and other users of the diagnostic statements to decide whether to record the lesser degrees of confidence (such as "provisional" if more information is yet to come, or "tentative" if more information is unlikely to become available) that are implied in these circumstances. Statements about the duration of symptoms are also intended as general guidelines rather than strict requirements; clinicians should use their own judgement about the appropriateness of choosing diagnoses when the duration of particular symptoms is slightly longer or shorter than that specified. The diagnostic guidelines should also provide a useful stimulus for clinical teaching, since they serve as a reminder about points of clinical practice that can be found in a fuller form in most textbooks of psychiatry. They may also be suitable for some types of -8- research projects, where the greater precision (and therefore restriction) of the diagnostic criteria for research are not required. These descriptions and guidelines carry no theoretical implications, and they do not pretend to be comprehensive statements about the current state of knowledge of the disorders. They are simply a set of symptoms and comments that have been agreed, by a large number of advisors and consultants in many different countries, to be a reasonable basis for defining the limits of categories in the classification of mental disorders. Principal differences between Chapter V(F) of ICD-10 and Chapter V of ICD-9 General principles of ICD-10 ICD-10 is much larger than ICD-9. Numeric codes (001-999) were used in ICD-9, whereas an alphanumeric coding scheme, based on codes with a single letter followed by two numbers at the three-character level (A00-Z99), has been adopted in ICD-10. This has significantly enlarged the number of categories available for the classification. Further detail is then provided by means of decimal numeric subdivisions at the four-character level. The chapter that dealt with mental disorders in ICD-9 had only 30 three-character categories (290-319); Chapter V(F) of ICD-10 has 100 such categories. A proportion of these categories has been left unused for the time being, so as to allow the introduction of changes into the classification without the need to redesign the entire system. ICD-10 as a whole is designed to be a central ("core") classification for a family of disease- and health-related classifications. Some members of the family of classifications are derived by using a fifth or even sixth character to specify more detail. In others, the categories are condensed to give broad groups suitable for use, for instance, in primary health care or general medical practice. There is a multiaxial presentation of Chapter V(F) of ICD-10 and a version for child psychiatric practice and research. The "family" also includes classifications that cover information not contained in the ICD, but having important medical or health implications, e.g. the classification of impairments, disabilities and handicaps, the classification of procedures in medicine, and the classification of reasons for encounter between patients and health workers. -9- Neurosis and psychosis The traditional division between neurosis and psychosis that was evident in ICD-9 (although deliberately left without any attempt to define these concepts) has not been used in ICD-10. However, the term "neurotic" is still retained for occasional use and occurs, for instance, in the heading of a major group (or block) of disorders F40-F48, "Neurotic, stress-related and somatoform disorders". Except for depressive neurosis, most of the disorders regarded as neuroses by those who use the concept are to be found in this block,and the remainder are in the subsequent blocks. Instead of following the neurotic-psychotic dichotomy, the disorders are now arranged in groups according to major common themes or descriptive likenesses, which makes for increased convenience of use. For instance, cyclothymia (F34.0) is in the block F30-F39, Mood [affective] disorders, rather than in F60-F69, Disorders of adult personality and behaviour; similarly, all disorders associated with the use of psychoactive substances are grouped together in F10-F19, regardless of their severity. "Psychotic" has been retained as a convenient descriptive term, particularly in F23, Acute and transient psychotic disorders. Its use does not involve assumptions about psychodynamic mechanisms, but simply indicates the presence of hallucinations, delusions, or a limited number of severe abnormalities of behaviour, such as gross excitement and overactivity, marked psychomotor retardation, and catatonic behaviour. Other differences between ICD-9 and ICD-10 All disorders attributable to an organic cause are grouped together in the block F00-F09, which makes the use of this part of the classification easier than the arrangement in the ICD-9. The new arrangement of mental and behavioural disorders due to psychoactive substance use in the block F10-F19 has also been found more useful than the earlier system. The third character indicates the substance used, the fourth and fifth characters the psychopathological syndrome, e.g. from acute intoxication and residual states; this allows the reporting of all disorders related to a substance even when only three-character categories are used. The block that covers schizophrenia, schizotypal states and delusional disorders (F20-F29) has been expanded by the introduction of new categories such as undifferentiated schizophrenia, postschizophrenic depression, and schizotypal disorder. The classification of acute short-lived psychoses, which are commonly seen in most developing countries, is considerably expanded compared with that in the ICD-9. Classification of affective disorders has been particularly influenced by the adoption of the principle of grouping together disorders with a common theme. Terms such as "neurotic depression" and "endogenous depression" are not used, but their close equivalents can be found in the different types and severities of depression now specified (including dysthymia (F34.1)). - 10 - The behavioural syndromes and mental disorders associated with physiological dysfunction and hormonal changes, such as eating disorders, nonorganic sleep disorders, and sexual dysfunctions, have been brought together in F50-F59 and described in greater detail than in ICD-9, because of the growing needs for such a classification in liaison psychiatry. Block F60-F69 contains a number of new disorders of adult behaviour such as pathological gambling, fire-setting, and stealing, as well as the more traditional disorders of personality. Disorders of sexual preference are clearly differentiated from disorders of gender identity, and homosexuality in itself is no longer included as a category. Some further comments about changes between the provisions for the coding of disorders specific to childhood and mental retardation can be found on pages 18-20. Problems of terminology Disorder The term "disorder" is used throughout the classification, so as to avoid even greater problems inherent in the use of terms such as "disease" and "illness". "Disorder" is not an exact term, but it is used here to imply the existence of a clinically recognizable set of symptoms or behaviour associated in most cases with distress and with interference with personal functions. Social deviance or conflict alone, without personal dysfunction, should not be included in mental disorder as defined here. Psychogenic and psychosomatic The term "psychogenic" has not been used in the titles of categories, in view of its different meanings in different languages and psychiatric traditions. It still occurs occasionally in the text, and should be taken to indicate that the diagnostician regards obvious life events or difficulties as playing an important role in the genesis of the disorder. "Psychosomatic" is not used for similar reasons and also because use of this term might be taken to imply that psychological factors play no role in the occurrence, course and outcome of other diseases that are not so described. Disorders described as psychosomatic in other classifications can be found here in F45.- (somatoform disorders), F50.- (eating disorders), F52.- (sexual dysfunction), and F54.- (psychological or behavioural factors associated with disorders or diseases classified elsewhere). It is particularly important to note category F54.- (category 316 in ICD-9) and to remember to use it for specifying the association of physical disorders, coded elsewhere in ICD-10, with an emotional causation. A common example would be the recording of psychogenic asthma or eczema by means of both F54 from Chapter V(F) and the appropriate code for the physical condition from other chapters in ICD-10. Impairment, disability, handicap and related terms - 11 - The terms "impairment", "disability" and "handicap" are used according to the recommendations of the system adopted by WHO.1 Occasionally, where justified by clinical tradition, the terms are used in a broader sense. See also pages 8 and 9 regarding dementia and its relationships with impairment, disability and handicap. Some specific points for users Children and adolescents Blocks F80-F89 (disorders of psychological development) and F90-F98 (behavioural and emotional disorders with onset usually occurring in childhood and adolescence) cover only those disorders that are specific to childhood and adolescence. A number of disorders placed in other categories can occur in persons of almost any age, and should be used for children and adolescents when required. Examples are disorders of eating (F50.-), sleeping (F51.-) and gender identity (F64.-). Some types of phobia occurring in children pose special problems for classification, as noted in the description of F93.1 (phobic anxiety disorder of childhood). Recording more than one diagnosis It is recommended that clinicians should follow the general rule of recording as many diagnoses as are necessary to cover the clinical picture. When recording more than one diagnosis, it is usually best to give one precedence over the others by specifying it as the main diagnosis, and to label any others as subsidiary or additional diagnoses. Precedence should be given to that diagnosis most relevant to the purpose for which the diagnoses are being collected; in clinical work this is often the disorder that gave rise to the consultation or contact with health services. In many cases it will be the disorder that necessitates admission to an inpatient, outpatient or day-care service. At other times, for example when reviewing the patient's whole career, the most important diagnosis may well be the "life-time" diagnosis, which could be different from the one most relevant to the immediate consultation (for instance a patient with chronic schizophrenia presenting for an episode of care because of symptoms of acute anxiety). If there is any doubt about the order in which to record several diagnoses, or the diagnostician is uncertain of the purpose for which information will be used, a useful rule is to record the diagnoses in the numerical order in which they appear in the classification. Recording diagnoses from other chapters of ICD-10 The use of other chapters of the ICD-10 system in addition to Chapter V(F) is strongly recommended. The categories most relevant to mental health services are listed in the Annex to this book. 1 International classification of impairments, disabilities and handicaps. Geneva, World Health Organization, 1980. - 12 - Notes on selected categories in the classification of mental and behavioural disorders in ICD-10 In the course of preparation of the ICD-10 chapter on mental disorder, certain categories attracted considerable interest and debate before a reasonable level of consensus could be achieved among all concerned. Brief notes are presented here on some of the issues that were raised. Dementia (F01-F03) and its relationships with impairment, disability and handicap Although a decline in cognitive abilities is essential for the diagnosis of dementia, no consequent interference with the performance of social roles, either within the family or with regard to employment, is used as a diagnostic guideline or criterion. This is a particular instance of a general principle that applies to the definitions of all the disorders in Chapter V(F) of ICD-10, adopted because of the wide variations between different cultures, religions, and nationalities in terms of work and social roles that are available, or regarded as appropriate. Nevertheless, once a diagnosis has been made using other information, the extent to which an individual's work, family, or leisure activities are hindered or even prevented is often a useful indicator of the severity of a disorder. This is an opportune moment to refer to the general issue of the relationships between symptoms, diagnostic criteria, and the system adopted by WHO for describing impairment, disability, and handicap.2 In terms of this system, impairment (i.e. a "loss or abnormality... of structure or function") is manifest psychologically by interference with mental functions such as memory, attention, and emotive functions. Many types of psychological impairment have always been recognized as psychiatric symptoms. To a lesser degree, some types of disability (defined in the WHO system as "a restriction or lack... of ability to perform an activity in the manner or within the range considered normal for a human being") have also conventionally been regarded as psychiatric symptoms. Examples of disability at the personal level include the ordinary, and usually necessary, activities of daily life involved in personal care and survival related to washing, dressing, eating, and excretion. Interference with these activities is often a direct consequence of psychological impairment, and is influenced little, if at all, by culture. Personal disabilities can therefore legitimately appear among diagnostic guidelines and criteria, particularly for dementia. In contrast, a handicap ("the disadvantage for an individual... that prevents or limits the performance of a role that is normal...for that individual") represents the effects of impairments or disabilities in a wide social context that may be heavily influenced by culture. Handicaps should therefore not be used as essential components of a diagnosis. 2 International classification of impairments, disabilities and handicaps. Geneva, World Health Organization, 1980. - 13 - Duration of symptoms required for schizophrenia (F20.-) Prodromal states Before the appearance of typical schizophrenic symptoms, there is sometimes a period of weeks or months - particularly in young people - during which a prodrome of nonspecific symptoms appears (such as loss of interest, avoiding the company of others, staying away from work, being irritable and oversensitive). These symptoms are not diagnostic of any particular disorder, but neither are they typical of the healthy state of the individual. They are often just as distressing to the family and as incapacitating to the patient as the more clearly morbid symptoms, such as delusions and hallucinations, which develop later. Viewed retrospectively, such prodromal states seem to be an important part of the development of the disorder, but little systematic information is available as to whether similar prodromes are common in other psychiatric disorders, or whether similar states appear and disappear from time to time in individuals who never develop any diagnosable psychiatric disorder. If a prodrome typical of and specific to schizophrenia could be identified, described reliably, and shown to be uncommon in those with other psychiatric disorders and those with no disorders at all, it would be justifiable to include a prodrome among the optional criteria for schizophrenia. For the purposes of ICD-10, it was considered that insufficient information is available on these points at present to justify the inclusion of a prodromal state as a contributor to this diagnosis. An additional, closely related, and still unsolved problem is the extent to which such prodromes can be distinguished from schizoid and paranoid personality disorders. Separation of acute and transient psychotic disorders (F23.-) from schizophrenia (F20.-) In ICD-10, the diagnosis of schizophrenia depends upon the presence of typical delusions, hallucinations or other symptoms (described on pages 86-89), and a minimum duration of 1 month is specified. Strong clinical traditions in several countries, based on descriptive though not epidemiological studies, contribute towards the conclusion that, whatever the nature of the dementia praecox of Kraepelin and the schizophrenias of Bleuler, it, or they, are not the same as very acute psychoses that have an abrupt onset, a short course of a few weeks or even days, and a favourable outcome. Terms such as "bouffée délirante", "psychogenic psychosis", "schizophreniform psychosis", "cycloid psychosis" and "brief reactive psychosis" indicate the widespread but diverse opinion and traditions that have developed. Opinions and evidence also vary as to whether transient but typical schizophrenic symptoms may occur with these disorders, and whether they are usually or always associated with acute psychological stress (bouffée délirante, at least, was originally described as not usually associated with an obvious psychological precipitant). - 14 - Given the present lack of knowledge about both schizophrenia and these more acute disorders, it was considered that the best option for ICD-10 would be to allow sufficient time for the symptoms of the acute disorders to appear, be recognized, and largely subside, before a diagnosis of schizophrenia was made. Most clinical reports and authorities suggest that, in the large majority of patients with these acute psychoses, onset of psychotic symptoms occurs over a few days, or over 1-2 weeks at most, and that many patients recover with or without medication within 2-3 weeks. It therefore seems appropriate to specify 1 month as the transition point between the acute disorders in which symptoms of the schizophrenic type have been a feature and schizophrenia itself. For patients with psychotic, but non-schizophrenic, symptoms that persist beyond the 1-month point, there is no need to change the diagnosis until the duration requirement of delusional disorder (F22.0) is reached (3 months, as discussed below). A similar duration suggests itself when acute symptomatic psychoses (amphetamine psychosis is the best example) are considered. Withdrawal of the toxic agent is usually followed by disappearance of the symptoms over 8-10 days, but since it often takes 7-10 days for the symptoms to become manifest and troublesome (and for the patient to present to the psychiatric services), the overall duration is often 20 days or more. About 30 days, or 1 month, would therefore seem an appropriate time to allow as an overall duration before calling the disorder schizophrenia, if the typical symptoms persist. To adopt a 1-month duration of typical psychotic symptoms as a necessary criterion for the diagnosis of schizophrenia rejects the assumption that schizophrenia must be of comparatively long duration. A duration of 6 months has been adopted in more than one national classification, but in the present state of ignorance there appear to be no advantages in restricting the diagnosis of schizophrenia in this way. In two large international collaborative studies on schizophrenia and related disorders3, the second of which was epidemiologically based, a substantial proportion of patients were found whose clear and typical schizophrenic symptoms lasted for more than 1 month but less than 6 months, and who made good, if not complete, recoveries from the disorder. It therefore seems best for the purposes of ICD-10 to avoid any assumption about necessary chronicity for schizophrenia, and to regard the term as descriptive of a syndrome with a variety of causes (many of which are still unknown) and a variety of outcomes, depending upon the balance of genetic, physical, social, and cultural influences. There has also been considerable debate about the most appropriate duration of symptoms to specify as necessary for the diagnosis of persistent delusional disorder (F22.-). Three months was finally chosen as being the least unsatisfactory, since to delay 3 The international pilot study of schizophrenia. Geneva, World Health Organization, 1973 (Offset Publication, No. 2). Sartorius, N. et al. Early manifestations and first contact incidence of schizophrenia in different cultures. A preliminary report on the initial evaluation phase of the WHO Collaborative Study on Determinants of Outcome of Severe Mental Disorders, Psychological medicine, 16: 909- 928 (1986). - 15 - the decision point to 6 months or more makes it necessary to introduce another intermediate category between acute and transient psychotic disorders (F23.-) and persistent delusional disorder. The whole subject of the relationship between the disorders under discussion awaits more and better information than is at present available; a comparatively simple solution, which gives precedence to the acute and transient states, seemed the best option, and perhaps one that will stimulate research. The principle of describing and classifying a disorder or group of disorders so as to display options rather than to use built-in assumptions, has been used for acute and transient psychotic disorders (F23.-); these and related points are discussed briefly in the introduction to that category (pages 97-99). The term "schizophreniform" has not been used for a defined disorder in this classification. This is because it has been applied to several different clinical concepts over the last few decades, and associated with various mixtures of characteristics such as acute onset, comparatively brief duration, atypical symptoms or mixtures of symptoms, and a comparatively good outcome. There is no evidence to suggest a preferred choice for its usage, so the case for its inclusion as a diagnostic term was considered to be weak. Moreover, the need for an intermediate category of this type is obviated by the use of F23.- (acute and transient psychotic disorders) and its subdivisions, together with the requirement of 1 month of psychotic symptoms for a diagnosis of schizophrenia. As guidance for those who do use schizophreniform as a diagnostic term, it has been inserted in several places as an inclusion term relevant to those disorders that have the most overlap with the meanings it has acquired. These are: "schizophreniform attack or psychosis, NOS" in F20.8 (other schizophrenia), and "brief schizophreniform disorder or psychosis" in F23.2 (acute schizophrenia-like psychotic disorder). Simple schizophrenia (F20.6) This category has been retained because of its continued use in some countries, and because of the uncertainty about its nature and its relationships to schizoid personality disorder and schizotypal disorder, which will require additional information for resolution. The criteria proposed for its differentiation highlight the problems of defining the mutual boundaries of this whole group of disorders in practical terms. Schizoaffective disorders (F25.-) The evidence at present available as to whether schizoaffective disorders (F25.-) as defined in the ICD-10 should be placed in block F20-F29 (schizophrenia, schizotypal and delusional disorders) or in F30-F39 (mood [affective] disorders) is fairly evenly balanced. The final decision to place it in F20-F29 was influenced by feedback from the field trials of the 1987 draft, and by comments resulting from the worldwide circulation of the same draft to member societies of the World Psychiatric Association. It is clear that widespread and strong clinical traditions exist that favour its retention among schizophrenia and delusional disorders. It is relevant to this discussion that, given a set of affective symptoms, the addition of only mood-incongruent delusions is not sufficient to change the diagnosis to a schizoaffective category. At least one typically schizophrenic - 16 - symptom must be present with the affective symptoms during the same episode of the disorder. Mood [affective] disorders (F30-F39) It seems likely that psychiatrists will continue to disagree about the classification of disorders of mood until methods of dividing the clinical syndromes are developed that rely at least in part upon physiological or biochemical measurement, rather than being limited as at present to clinical descriptions of emotions and behaviour. As long as this limitation persists, one of the major choices lies between a comparatively simple classification with only a few degrees of severity, and one with greater details and more subdivisions. The 1987 draft of ICD-10 used in the field trials had the merit of simplicity, containing, for example, only mild and severe depressive episodes, no separation of hypomania from mania, and no recommendation to specify the presence or absence of familiarly clinical concepts, such as the "somatic" syndrome or affective hallucinations and delusions. However, feedback from many of the clinicians involved in the field trials, and other comments received from a variety of sources, indicated a widespread demand for opportunities to specify several grades of depression and the other features noted above. In addition, it is clear from the preliminary analysis of field trial data that in many centres the category of "mild depressive episode" often had a comparatively low inter-rater reliability. It has also become evident that the views of clinicians on the required number of subdivisions of depression are strongly influenced by the types of patient they encounter most frequently. Those working in primary care, outpatient clinics and liaison settings need ways of describing patients with mild but clinically significant states of depression, whereas those whose work is mainly with inpatients frequently need to use the more extreme categories. Further consultations with experts on affective disorders resulted in the present versions. Options for specifying several aspects of affective disorders have been included, which, although still some way from being scientifically respectable, are regarded by psychiatrists in many parts of the world as clinically useful. It is hoped that their inclusion will stimulate further discussion and research into their true clinical value. Unsolved problems remain about how best to define and make diagnostic use of the incongruence of delusions with mood. There would seem to be both enough evidence and sufficient clinical demand for the inclusion of provisions for mood-congruent or mood-incongruent delusions to be included, at least as an "optional extra". Recurrent brief depressive disorder Since the introduction of ICD-9, sufficient evidence has accumulated to justify the provision of a special category for the brief episodes of depression that meet the severity criteria but not the duration criteria for depressive episode (F32.-). These recurrent states are of unclear nosological significance and the provision of a category for their recording - 17 - should encourage the collection of information that will lead to a better understanding of their frequency and long-term course. Agoraphobia and panic disorder There has been considerable debate recently as to which of agoraphobia and panic disorder should be regarded as primary. From an international and cross-cultural perspective, the amount and type of evidence available does not appear to justify rejection of the still widely accepted notion that the phobic disorder is best regarded as the prime disorder, with attacks of panic usually indicating its severity. Mixed categories of anxiety and depression Psychiatrists and others, especially in developing countries, who see patients in primary health care services should find particular use for F41.2 (mixed anxiety and depressive disorder), F41.3 (other mixed disorders), the various subdivisions of F43.2 (adjustment disorder), and F44.7 (mixed dissociative [conversion] disorder). The purpose of these categories is to facilitate the description of disorders manifest by a mixture of symptoms for which a simpler and more traditional psychiatric label is not appropriate but which nevertheless represent significantly common, severe states of distress and interference with functioning. They also result in frequent referral to primary care, medical and psychiatric services. Difficulties in using these categories reliably may be encountered, but it is important to test them and - if necessary - improve their definition. Dissociative and somatoform disorders, in relation to hysteria The term "hysteria" has not been used in the title for any disorder in Chapter V(F) of ICD-10 because of its many and varied shades of meaning. Instead, "dissociative" has been preferred, to bring together disorders previously termed hysteria, of both dissociative and conversion types. This is largely because patients with the dissociative and conversion varieties often share a number of other characteristics, and in addition they frequently exhibit both varieties at the same or different times. It also seems reasonable to presume that the same (or very similar) psychological mechanisms are common to both types of symptoms. There appears to be widespread international acceptance of the usefulness of grouping together several disorders with a predominantly physical or somatic mode of presentation under the term "somatoform". For the reasons already given, however, this new concept was not considered to be an adequate reason for separating amnesias and fugues from dissociative sensory and motor loss. If multiple personality disorder (F44.81) does exist as something other than a culture-specific or even iatrogenic condition, then it is presumably best placed among the dissociative group. - 18 - Neurasthenia Although omitted from some classification systems, neurasthenia has been retained as a category in ICD-10, since this diagnosis is still regularly and widely used in a number of countries. Research carried out in various settings has demonstrated that a significant proportion of cases diagnosed as neurasthenia can also be classified under depression or anxiety: there are, however, cases in which the clinical syndrome does not match the description of any other category but does meet all the criteria specified for a syndrome of neurasthenia. It is hoped that further research on neurasthenia will be stimulated by its inclusion as a separate category. Culture-specific disorders The need for a separate category for disorders such as latah, amok, koro, and a variety of other possibly culture-specific disorders has been expressed less often in recent years. Attempts to identify sound descriptive studies, preferably with an epidemiological basis, that would strengthen the case for these inclusions as disorders clinically distinguishable from others already in the classification have failed, so they have not been separately classified. Descriptions of these disorders currently available in the literature suggest that they may be regarded as local variants of anxiety, depression, somatoform disorder, or adjustment disorder; the nearest equivalent code should therefore be used if required, together with an additional note of which culture-specific disorder is involved. There may also be prominent elements of attention-seeking behaviour or adoption of the sick role akin to that described in F68.1 (intentional production or feigning of symptoms or disabilities), which can also be recorded. Mental and behavioural disorders associated with the puerperium (F53.-) This category is unusual and apparently paradoxical in carrying a recommendation that it should be used only when unavoidable. Its inclusion is a recognition of the very real practical problems in many developing countries that make the gathering of details about many cases of puerperal illness virtually impossible. However, even in the absence of sufficient information to allow a diagnosis of some variety of affective disorder (or, more rarely, schizophrenia), there will usually be enough known to allow diagnosis of a mild (F53.0) or severe (F53.1) disorder; this subdivision is useful for estimations of workload, and when decisions are to be made about provision of services. The inclusion of this category should not be taken to imply that, given adequate information, a significant proportion of cases of postpartum mental illness cannot be classified in other categories. Most experts in this field are of the opinion that a clinical picture of puerperal psychosis is so rarely (if ever) reliably distinguishable from affective disorder or schizophrenia that a special category is not justified. Any psychiatrist who is of the minority opinion that special postpartum psychoses do indeed exist may use this category, but should be aware of its real purpose. - 19 - Disorders of adult personality (F60.-) In all current psychiatric classifications, disorders of adult personality include a variety of severe problems, whose solution requires information that can come only from extensive and time-consuming investigations. The difference between observations and interpretation becomes particularly troublesome when attempts are made to write detailed guidelines or diagnostic criteria for these disorders; and the number of criteria that must be fulfilled before a diagnosis is regarded as confirmed remains an unsolved problem in the light of present knowledge. Nevertheless, the attempts that have been made to specify guidelines and criteria for this category may help to demonstrate that a new approach to the description of personality disorders is required. After initial hesitation, a brief description of borderline personality disorder (F60.31) was finally included as a subcategory of emotionally unstable personality disorder (F60.3), again in the hope of stimulating investigations. Other disorders of adult personality and behaviour (F68) Two categories that have been included here but were not present in ICD-9 are F68.0, elaboration of physical symptoms for psychological reasons, and F68.1, intentional production or feigning of symptoms or disabilities, either physical or psychological [factitious disorder]. Since these are, strictly speaking, disorders of role or illness behaviour, it should be convenient for psychiatrists to have them grouped with other disorders of adult behaviour. Together with malingering (Z76.5), which has always been outside Chapter V of the ICD, the disorders from a trio of diagnoses often need to be considered together. The crucial difference between the first two and malingering is that the motivation for malingering is obvious and usually confined to situations where personal danger, criminal sentencing, or large sums of money are involved. Mental retardation (F70-F79) The policy for Chapter V(F) of ICD-10 has always been to deal with mental retardation as briefly and as simply as possible, acknowledging that justice can be done to this topic only by means of a comprehensive, possibly multiaxial, system. Such a system needs to be developed separately, and work to produce appropriate proposals for international use is now in progress. - 20 - Disorders with onset specific to childhood F80-F89 Disorders of psychological development Disorders of childhood such as infantile autism and disintegrative psychosis, classified in ICD-9 as psychoses, are now more appropriately contained in F84.-, pervasive developmental disorders. While some uncertainty remains about their nosological status, it has been considered that sufficient information is now available to justify the inclusion of the syndromes of Rett and Asperger in this group as specified disorders. Overactive disorder associated with mental retardation and stereotyped movements (F84.4) has been included in spite of its mixed nature, because evidence suggests that this may have considerable practical utility. F90-F98 Behavioural and emotional disorders with onset usually occurring in childhood and adolescence Differences in international opinion about the broadness of the concept of hyperkinetic disorder have been a well-known problem for many years, and were discussed in detail at the meetings between WHO advisors and other experts held under the auspices of the WHO-ADAMHA joint project. Hyperkinetic disorder is now defined more broadly in ICD-10 than it was in ICD-9. The ICD-10 definition is also different in the relative emphasis given to the constituent symptoms of the overall hyperkinetic syndrome; since recent empirical research was used as the basis for the definition, there are good reasons for believing that the definition in ICD-10 represents a significant improvement. Hyperkinetic conduct disorder (F90.1) is one of the few examples of a combination category remaining in ICD-10, Chapter V(F). The use of this diagnosis indicates that the criteria for both hyperkinetic disorder (F90.-) and conduct disorder (F91.-) are fulfilled. These few exceptions to the general rule were considered justified on the grounds of clinical convenience in view of the frequent coexistence of those disorders and the demonstrated later importance of the mixed syndrome. However, it is likely that The ICD-10 Classification of Mental and Behavioural Disorders: Diagnostic criteria for research (DCR-10) will recommend that, for research purposes, individual cases in these categories be described in terms of hyperactivity, emotional disturbance, and severity of conduct disorder (in addition to the combination category being used as an overall diagnosis). Oppositional defiant disorder (F91.3) was not in ICD-9, but has been included in ICD-10 because of evidence of its predictive potential for later conduct problems. There is, however, a cautionary note recommending its use mainly for younger children. The ICD-9 category 313 (disturbances of emotion specific to childhood and adolescence) has been developed into two separate categories for ICD-10, namely emotional disorders with onset specific to childhood (F93.-) and disorders of social functioning with onset specific to childhood and adolescence (F94.-). This is because of the continuing need for a differentiation between children and adults with respect to various forms of morbid anxiety and related emotions. The frequency with which emotional disorders in childhood are followed by no significant similar disorder in adult life, and the frequent onset of neurotic disorders in adults are clear indicators of this - 21 - need. The key defining criterion used in ICD-10 is the appropriateness to the developmental stage of the child of the emotion shown, plus an unusual degree of persistence with disturbance of function. In other words, these childhood disorders are significant exaggerations of emotional states and reactions that are regarded as normal for the age in question when occurring in only a mild form. If the content of the emotional state is unusual, or if it occurs at an unusual age, the general categories elsewhere in the classification should be used. In spite of its name, the new category F94.- (disorders of social functioning with onset specific to childhood and adolescence) does not go against the general rule for ICD-10 of not using interference with social roles as a diagnostic criterion. The abnormalities of social functioning involved in F94.- are of a limited number and contained within the parent-child relationship and the immediate family; these relationships do not have the same connotations or show the same cultural variations as those formed in the context of work or of providing for the family, which are excluded from use as diagnostic criteria. A number of categories that will be used frequently by child psychiatrists, such as eating disorders (F50.-), nonorganic sleep disorders (F51.-), and gender identity disorders (F64.-), are to be found in the general sections of the classifications because of their frequent onset and occurrence in adults as well as children. Nevertheless, clinical features specific to childhood were thought to justify the additional categories of feeding disorder of infancy (F98.2) and pica of infancy and childhood (F98.3). Users of blocks F80-F89 and F90-F98 also need to be aware of the contents of the neurological chapter of ICD-10 (Chapter VI(G)). This contains syndromes with predominantly physical manifestations and clear "organic" etiology, of which the Kleine-Levin syndrome (G47.8) is of particular interest to child psychiatrists. Unspecified mental disorder (F99) There are practical reasons why a category for the recording of "unspecified mental disorder" is required in ICD-10, but the subdivision of the whole of the classificatory space available for Chapter V(F) into 10 blocks, each covering a specific area, posed a problem for this requirement. It was decided that the least unsatisfactory solution was to use the last category in the numerical order of the classification, i.e. F99. Deletion of categories proposed for earlier drafts of ICD-10 The process of consultation and reviews of the literature that preceded the drafting of Chapter V(F) of ICD-10 resulted in numerous proposals for changes. Decisions on whether to accept or reject proposals were influenced by a number of factors. These included the results of the field tests of the classification, consultations with heads of WHO collaborative centres, results of collaboration with nongovernmental organizations, advice from members of WHO expert advisory panels, results of translations of the classification, and the constraints of the rules governing the structure of the ICD as a whole. - 22 - It was normally easy to reject proposals that were idiosyncratic and unsupported by evidence, and to accept others that were accompanied by sound justification. Some proposals, although reasonable when considered in isolation, could not be accepted because of the implications that even minor changes to one part of the classification would have for other parts. Some other proposals had clear merit, but more research would be necessary before they could be considered for international use. A number of these proposals included in early versions of the general classification were omitted from the final version, including "accentuation of personality traits" and "hazardous use of psychoactive substances". It is hoped that research into the status and usefulness of these and other innovative categories will continue. - 23 - List of categories F00-F09 Organic, including symptomatic, mental disorders F00 Dementia in Alzheimer's disease F00.0Dementia in Alzheimer's disease with early onset F00.1Dementia in Alzheimer's disease with late onset F00.2Dementia in Alzheimer's disease, atypical or mixed type F00.9Dementia in Alzheimer's disease, unspecified F01Vascular dementia F01.0Vascular dementia of acute onset F01.1Multi-infarct dementia F01.2Subcortical vascular dementia F01.3Mixed cortical and subcortical vascular dementia F01.8Other vascular dementia F01.9Vascular dementia, unspecified F02Dementia in other diseases classified elsewhere F02.0Dementia in Pick's disease F02.1Dementia in Creutzfeldt-Jakob disease F02.2Dementia in Huntington's disease F02.3Dementia in Parkinson's disease F02.4Dementia in human immunodeficiency virus [HIV] disease F02.8Dementia in other specified diseases classified elsewhere F03Unspecified dementia A fifth character may be added to specify dementia in F00-F03, as follows:.x0 Without additional symptoms.x1 Other symptoms, predominantly delusional.x2 Other symptoms, predominantly hallucinatory.x3 Other symptoms, predominantly depressive.x4 Other mixed symptoms F04Organic amnesic syndrome, not induced by alcohol and other substances F05Delirium, not induced by alcohol and other psychoactive substances F05.0Delirium, not superimposed on dementia, so described F05.1Delirium, superimposed on dementia F05.8Other delirium F05.9Delirium, unspecified F06Other mental disorders due to brain damage and dysfunction and to physical disease F06.0Organic hallucinosis F06.1Organic catatonic disorder - 24 - F06.2Organic delusional [schizophrenia-like] disorder F06.3Organic mood [affective] disorders.30 Organic manic disorder.31 Organic bipolar affective disorder.32 Organic depressive disorder.33 Organic mixed affective disorder F06.4Organic anxiety disorder F06.5Organic dissociative disorder F06.6Organic emotionally labile [asthenic] disorder F06.7Mild cognitive disorder F06.8Other specified mental disorders due to brain damage and dysfunction and to physical disease F06.9Unspecified mental disorder due to brain damage and dysfunction and to physical disease F07Personality and behavioural disorder due to brain disease, damage and dysfunction F07.0Organic personality disorder F07.1Postencephalitic syndrome F07.2Postconcussional syndrome F07.8Other organic personality and behavioural disorder due to brain disease, damage and dysfunction F09Unspecified organic or symptomatic mental disorder - 25 - F10--F19 Mental and behavioural disorders due to psychoactive substance use F10.-Mental and behavioural disorders due to use of alcohol F11.-Mental and behavioural disorders due to use of opioids F12.-Mental and behavioural disorders due to use of cannabinoids F13.-Mental and behavioural disorders due to use of sedatives or hypnotics F14.-Mental and behavioural disorders due to use of cocaine F15.-Mental and behavioural disorders due to use of other stimulants, including caffeine F16.-Mental and behavioural disorders due to use of hallucinoeens F17.-Mental and behavioural disorders due to use of tobacco F18.-Mental and behavioural disorders due to use of volatile solvents F19.-Mental and behavioural disorders due to multiple drug use and use of other psychoactive substances Four- and five-character categories may be used to specify the clinical conditions, as follows: F1x.0 Acute intoxication.00 Uncomplicated.01 With trauma or other bodily injury.02 With other medical complications.03 With delirium.04 With perceptual distortions.05 With coma.06 With convulsions.07 Pathological intoxication F1x.1 Harmful use F1x.2 Dependence syndrome.20 Currently abstinent.21 Currently abstinent, but in a protected environment.22 Currently on a clinically supervised maintenance or replacement regime [controlled dependence].23 Currently abstinent, but receiving treatment with aversive or blocking drugs.24 Currently using the substance [active - 26 - dependence].25 Continuous use.26 Episodic use [dipsomania] F1x.3 Withdrawal state.30 Uncomplicated.31 With convulsions F1x.4 Withdrawal state with delirium.40 Without convulsions.41 With convulsions F1x.5 Psychotic disorder.50 Schizophrenia-like.51 Predominantly delusional.52 Predominantly hallucinatory.53 Predominantly polymorphic.54 Predominantly depressive symptoms.55 Predominantly manic symptoms.56 Mixed F1x.6 Amnesic syndrome F1x.7 Residual and late-onset psychotic disorder.70 Flashbacks.71 Personality or behaviour disorder.72 Residual affective disorder.73 Dementia.74 Other persisting cognitive impairment.75 Late-onset psychotic disorder F1x.8 Other mental and behavioural disorders F1x.9 Unspecified mental and behavioural disorder - 27 - F20-F29 Schizophrenia, schizotypal and delusional disorders F20 Schizophrenia F20.0 Paranoid schizophrenia F20.1 Hebephrenic schizophrenia F20.2 Catatonic schizophrenia F20.3 Undifferentiated schizophrenia F20.4 Post-schizophrenic depression F20.5 Residual schizophrenia F20.6 Simple schizophrenia F20.8 Other schizophrenia F20.9 Schizophrenia, unspecified A fifth character may be used to classify course:.x0 Continuous.x1 Episodic with progressive deficit.x2 Episodic with stable deficit.x3 Episodic remittent.x4 Incomplete remission.x5 Complete remission.x6 Other.x9 Course uncertain, period of observation too short F21 Schizotypal disorder F22 Persistent delusional disorders F22.0 Delusional disorder F22.8 Other persistent delusional disorders F22.9 Persistent delusional disorder, unspecified F23 Acute and transient psychotic disorders F23.0 Acute polymorphic psychotic disorder without symptoms of schizophrenia F23.1 Acute polymorphic psychotic disorder with symptoms of schizophrenia F23.2 Acute schizophrenia-like psychotic disorder F23.3 Other acute predominantly delusional psychotic disorders F23.8 Other acute and transient psychotic disorders F23.9 Acute and transient psychotic disorders unspecified A fifth character may be used to identify the presence or absence of associated acute stress:.x0 Without associated acute stress.x1 With associated acute stress - 28 - F24 Induced delusional disorder F25 Schizoaffective disorders F25.0 Schizoaffective disorder, manic type F25.1 Schizoaffective disorder, depressive type F25.2 Schizoaffective disorder, mixed type F25.8 Other schizoaffective disorders F25.9 Schizoaffective disorder, unspecified F28 Other nonorganic psychotic disorders F29 Unspecified nonorganic psychosis - 29 - F30-F39 Mood [affective] disorders Overview of this block F30 Manic episode F30.0 Hypomania F30.1 Mania without psychotic symptoms F30.2 Mania with psychotic symptoms F30.8 Other manic episodes F30.9 Manic episode, unspecified F31 Bipolar affective disorder F31.0 Bipolar affective disorder, current episode hypomanic F31.1 Bipolar affective disorder, current episode manic without psychotic symptoms F31.2 Bipolar affective disorder, current episode manic with psychotic symptoms F31.3Bipolar affective disorder, current episode mild or moderate depression.30 Without somatic syndrome.31 With somatic syndrome F31.4 Bipolar affective disorder, current episode severe depression without psychotic symptoms F31.5 Bipolar affective disorder, current episode severe depression with psychotic symptoms F31.6 Bipolar affective disorder, current episode mixed F31.7 Bipolar affective disorder, currently in remission F31.8 Other bipolar affective disorders F31.9 Bipolar affective disorder, unspecified F32 Depressive episode F32.0 Mild depressive episode.00 Without somatic syndrome.01 With somatic syndrome F32.1 Moderate depressive episode.10 Without somatic syndrome.11 With somatic syndrome F32.2 Severe depressive episode without psychotic symptoms F32.3 Severe depressive episode with psychotic symptoms F32.8 Other depressive episodes F32.9 Depressive episode, unspecified - 30 - F33 Recurrent depressive disorder F33.0 Recurrent depressive disorder, current episode mild.00 Without somatic syndrome.01 With somatic syndrome F33.1 Recurrent depressive disorder, current episode moderate.10 Without somatic syndrome.11 With somatic syndrome F33.2 Recurrent depressive disorder, current episode severe without psychotic symptoms F33.3 Recurrent depressive disorder, current episode severe with psychotic symptoms F33.4 Recurrent depressive disorder, currently in remission F33.8 Other recurrent depressive disorders F33.9 Recurrent depressive disorder, unspecified F34 Persistent mood [affective] disorders F34.0 Cyclothymia F34.1 Dysthymia F34.8 Other persistent mood [affective] disorders F34.9 Persistent mood [affective] disorder, unspecified F38 Other mood [affective] disorders F38.0 Other single mood [affective] disorders.00 Mixed affective episode F38.1 Other recurrent mood [affective] disorders.10 Recurrent brief depressive disorder F38.8 Other specified mood [affective] disorders F39 Unspecified mood [affective] disorder - 31 - F40-F48 Neurotic, stress-related and somatoform disorders F40 Phobic anxiety disorders F40.0 Agoraphobia.00 Without panic disorder.01 With panic disorder F40.1 Social phobias F40.2 Specific (isolated) phobias F40.8 Other phobic anxiety disorders F40.9 Phobic anxiety disorder, unspecified F41 Other anxiety disorders F41.0 Panic disorder [episodic paroxysmal anxiety] F41.1 Generalized anxiety disorder F41.2 Mixed anxiety and depressive disorder F41.3 Other mixed anxiety disorders F41.8 Other specified anxiety disorders F41.9 Anxiety disorder, unspecified F42 Obsessive - compulsive disorder F42.0 Predominantly obsessional thoughts or ruminations F42.1 Predominantly compulsive acts [obsessional rituals] F42.2 Mixed obsessional thoughts and acts F42.8 Other obsessive - compulsive disorders F42.9 Obsessive - compulsive disorder, unspecified F43 Reaction to severe stress, and adjustment disorders F43.0 Acute stress reaction F43.1 Post-traumatic stress disorder F43.2 Adjustment disorders.20 Brief depressive reaction.21 Prolonged depressive reaction.22 Mixed anxiety and depressive reaction.23 With predominant disturbance of other emotions.24 With predominant disturbance of conduct.25 With mixed disturbance of emotions and conduct.28 With other specified predominant symptoms F43.8 Other reactions to severe stress F43.9 Reaction to severe stress, unspecified F44 Dissociative [conversion] disorders F44.0 Dissociative amnesia F44.1 Dissociative fugue F44.2 Dissociative stupor F44.3 Trance and possession disorders F44.4 Dissociative motor disorders - 32 - F44.5 Dissociative convulsions F44.6 Dissociative anaesthesia and sensory loss F44.7 Mixed dissociative [conversion] disorders F44.8 Other dissociative [conversion] disorders.80 Ganser's syndrome.81 Multiple personality disorder.82 Transient dissociative [conversion] disorders occurring in childhood and adolescence.88 Other specified dissociative [conversion] disorders F44.9 Dissociative [conversion] disorder, unspecified F45 Somatoform disorders F45.0 Somatization disorder F45.1 Undifferentiated somatoform disorder F45.2 Hypochondriacal disorder F45.3 Somatoform autonomic dysfunction.30 Heart and cardiovascular system.31 Upper gastrointestinal tract.32 Lower gastrointestinal tract.33 Respiratory system.34 Genitourinary system.38 Other organ or system F45.4 Persistent somatoform pain disorder F45.8 Other somatoform disorders F45.9 Somatoform disorder, unspecified F48 Other neurotic disorders F48.0 Neurasthenia F48.1 Depersonalization - derealization syndrome F48.8 Other specified neurotic disorders F48.9 Neurotic disorder, unspecified - 33 - F50-F59 Behavioural syndromes associated with physiological disturbances and physical factors F50 Eating disorders F50.0 Anorexia nervosa F50.1 Atypical anorexia nervosa F50.2 Bulimia nervosa F50.3 Atypical bulimia nervosa F50.4 Overeating associated with other psychological disturbances F50.5 Vomiting associated with other psychological disturbances F50.8 Other eating disorders F50.9 Eating disorder, unspecified F51 Nonorganic sleep disorders F51.0 Nonorganic insomnia F51.1 Nonorganic hypersomnia F51.2 Nonorganic disorder of the sleep-wake schedule F51.3 Sleepwalking [somnambulism] F51.4 Sleep terrors [night terrors] F51.5 Nightmares F51.8 Other nonorganic sleep disorders F51.9 Nonorganic sleep disorder, unspecified F52 Sexual dysfunction, not caused by organic disorder or disease F52.0 Lack or loss of sexual desire F52.1 Sexual aversion and lack of sexual enjoyment.10 Sexual aversion.11 Lack of sexual enjoyment F52.2 Failure of genital response F52.3 Orgasmic dysfunction F52.4 Premature ejaculation F52.5 Nonorganic vaginismus F52.6 Nonorganic dyspareunia F52.7 Excessive sexual drive F52.8 Other sexual dysfunction, not caused by organic disorders or disease F52.9 Unspecified sexual dysfunction, not caused by organic disorder or disease F53Mental and behavioural disorders associated with the puerperium, not elsewhere classified F53.0 Mild mental and behavioural disorders associated with the puerperium, not elsewhere classified - 34 - F53.1 Severe mental and behavioural disorders associated with the puerperium, not elsewhere classified F53.8 Other mental and behavioural disorders associated with the puerperium, not elsewhere classified F53.9 Puerperal mental disorder, unspecified F54Psychological and behavioural factors associated with disorders or diseases classified elsewhere F55 Abuse of non-dependence-producing substances F55.0 Antidepressants F55.1 Laxatives F55.2 Analgesics F55.3 Antacids F55.4 Vitamins F55.5 Steroids or hormones F55.6 Specific herbal or folk remedies F55.8 Other substances that do not produce dependence F55.9 Unspecified F59Unspecified behavioural syndromes associated with physiological disturbances and physical factors - 35 - F60-F69 Disorders of adult personality and behaviour F60 Specific personality disorders F60.0 Paranoid personality disorder F60.1 Schizoid personality disorder F60.2 Dissocial personality disorder F60.3 Emotionally unstable personality disorder.30 Impulsive type.31 Borderline type F60.4 Histrionic personality disorder F60.5 Anankastic personality disorder F60.6 Anxious [avoidant] personality disorder F60.7 Dependent personality disorder F60.8 Other specific personality disorders F60.9 Personality disorder, unspecified F61 Mixed and other personality disorders F61.0 Mixed personality disorders F61.1 Troublesome personality changes F62 Enduring personality changes, not attributable to brain damage and disease F62.0 Enduring personality change after catastrophic experience F62.1 Enduring personality change after psychiatric illness F62.8 Other enduring personality changes F62.9 Enduring personality change, unspecified F63 Habit and impulse disorders F63.0 Pathological gambling F63.1 Pathological fire-setting [pyromania] F63.2 Pathological stealing [kleptomania] F63.3 Trichotillomania F63.8 Other habit and impulse disorders F63.9 Habit and impulse disorder, unspecified F64 Gender identity disorders F64.0 Transsexualism F64.1 Dual-role transvestism F64.2 Gender identity disorder of childhood F64.8 Other gender identity disorders F64.9 Gender identity disorder, unspecified F65 Disorders of sexual preference F65.0 Fetishism F65.1 Fetishistic transvestism F65.2 Exhibitionism F65.3 Voyeurism F65.4 Paedophilia - 36 - F65.5 Sadomasochism F65.6 Multiple disorders of sexual preference F65.8 Other disorders of sexual preference F65.9 Disorder of sexual preference, unspecified F66 Psychological and behavioural disorders associated with sexual development and orientation F66.0 Sexual maturation disorder F66.1 Egodystonic sexual orientation F66.2 Sexual relationship disorder F66.8 Other psychosexual development disorders F66.9 Psychosexual development disorder, unspecified A fifth character may be used to indicate association with:.x0 Heterosexuality.x1 Homosexuality.x2 Bisexuality.x8 Other, including prepubertal F68 Other disorders of adult personality and behaviour F68.0 Elaboration of physical symptoms for psychological reasons F68.1 Intentional production or feigning of symptoms or disabilities, either physical or psychological [factitious disorder] F68.8 Other specified disorders of adult personality and behaviour F69 Unspecified disorder of adult personality and behaviour - 37 - F70-F79 Mental retardation F70 Mild mental retardation F71 Moderate mental retardation F72 Severe mental retardation F73 Profound mental retardation F78 Other mental retardation F79 Unspecified mental retardation A fourth character may be used to specify the extent of associated behavioural impairment: F7x.0 No, or minimal, impairment of behaviour F7x.1 Significant impairment of behaviour requiring attention or treatment F7x.8 Other impairments of behaviour F7x.9 Without mention of impairment of behaviour - 38 - F80-F89 Disorders of psychological development F80 Specific developmental disorders of speech and language F80.0 Specific speech articulation disorder F80.1 Expressive language disorder F80.2 Receptive language disorder F80.3 Acquired aphasia with epilepsy [Landau-Kleffner syndrome] F80.8 Other developmental disorders of speech and language F80.9 Developmental disorder of speech and language, unspecified F81 Specific developmental disorders of scholastic skills F81.0 Specific reading disorder F81.1 Specific spelling disorder F81.2 Specific disorder of arithmetical skills F81.3 Mixed disorder of scholastic skills F81.8 Other developmental disorders of scholastic skills F81.9 Developmental disorder of scholastic skills, unspecified F82 Specific developmental disorder of motor function F83 Mixed specific developmental disorders F84 Pervasive developmental disorders F84.0 Childhood autism F84.1 Atypical autism F84.2 Rett's syndrome F84.3 Other childhood disintegrative disorder F84.4Overactive disorder associated with mental retardation and stereotyped movements F84.5 Asperger's syndrome F84.8 Other pervasive developmental disorders F84.9 Pervasive developmental disorder, unspecified F88 Other disorders of psychological development F89 Unspecified disorder of psychological development - 39 - F90-F98 Behavioural and emotional disorders with onset usually occurring in childhood and adolescence F90 Hyperkinetic disorders F90.0 Disturbance of activity and attention F90.1 Hyperkinetic conduct disorder F90.8 Other hyperkinetic disorders F90.9 Hyperkinetic disorder, unspecified F91 Conduct disorders F91.0 Conduct disorder confined to the family context F91.1 Unsocialized conduct disorder F91.2 Socialized conduct disorder F91.3 Oppositional defiant disorder F91.8 Other conduct disorders F91.9 Conduct disorder, unspecified F92 Mixed disorders of conduct and emotions F92.0 Depressive conduct disorder F92.8 Other mixed disorders of conduct and emotions F92.9 Mixed disorder of conduct and emotions, unspecified F93 Emotional disorders with onset specific to childhood F93.0 Separation anxiety disorder of childhood F93.1 Phobic anxiety disorder of childhood F93.2 Social anxiety disorder of childhood F93.3 Sibling rivalry disorder F93.8 Other childhood emotional disorders F93.9 Childhood emotional disorder, unspecified F94 Disorders of social functioning with onset specific to childhood and adolescence F94.0 Elective mutism F94.1 Reactive attachment disorder of childhood F94.2 Disinhibited attachment disorder of childhood F94.8 Other childhood disorders of social functioning F94.9 Childhood disorder of social functioning, unspecified F95 Tic disorders F95.0 Transient tic disorder F95.1 Chronic motor or vocal tic disorder F95.2 Combined vocal and multiple motor tic disorder [de la Tourette's syndrome] F95.8 Other tic disorders F95.9 Tic disorder, unspecified - 40 - F98 Other behavioural and emotional disorders with onset usually occurring in childhood and adolescence F98.0 Nonorganic enuresis F98.1 Nonorganic encopresis F98.2 Feeding disorder of infancy and childhood F98.3 Pica of infancy and childhood F98.4 Stereotyped movement disorders F98.5 Stuttering [stammering] F98.6 Cluttering F98.8Other specified behavioural and emotional disorders with onset usually occurring in childhood and adolescence F98.9Unspecified behavioural and emotional disorders with onset usually occurring in childhood and adolescence F99 Unspecified mental disorder F99 Mental disorder, not otherwise specified - 41 - Clinical descriptions and diagnostic guidelines - 42 - F00-F09 Organic, including symptomatic, mental disorders Overview of this block F00 Dementia in Alzheimer's disease F00.0Dementia in Alzheimer's disease with early onset F00.1Dementia in Alzheimer's disease with late onset F00.2Dementia in Alzheimer's disease, atypical or mixed type F00.9Dementia in Alzheimer's disease, unspecified F01Vascular dementia F01.0Vascular dementia of acute onset F01.1Multi-infarct dementia F01.2Subcortical vascular dementia F01.3Mixed cortical and subcortical vascular dementia F01.8Other vascular dementia F01.9Vascular dementia, unspecified F02Dementia in other diseases classified elsewhere F02.0Dementia in Pick's disease F02.1Dementia in Creutzfeldt-Jakob disease F02.2Dementia in Huntington's disease F02.3Dementia in Parkinson's disease F02.4Dementia in human immunodeficiency virus [HIV] disease F02.8Dementia in other specified diseases classified elsewhere F03Unspecified dementia A fifth character may be added to specify dementia in F00-F03, as`follows:.x0 Without additional symptoms.x1 Other symptoms, predominantly delusional.x2 Other symptoms, predominantly hallucinatory.x3 Other symptoms, predominantly depressive.x4 Other mixed symptoms F04Organic amnesic syndrome, not induced by alcohol and other psychoactive substances F05Delirium, not induced by alcohol and other psychoactive substances F05.0Delirium, not superimposed on dementia, so described F05.1Delirium, superimposed on dementia F05.8Other delirium F05.9Delirium, unspecified F06Other mental disorders due to brain damage and dysfunction and to physical disease F06.0Organic hallucinosis F06.1Organic catatonic disorder F06.2Organic delusional [schizophrenia-like] disorder - 43 - F06.3Organic mood [affective] disorders.30 Organic manic disorder.31 Organic bipolar disorder.32 Organic depressive disorder.33 Organic mixed affective disorder F06.4Organic anxiety disorder F06.5Organic dissociative disorder F06.6Organic emotionally labile [asthenic] disorder F06.7Mild cognitive disorder F06.8Other specified mental disorders due to brain damage and dysfunction and to physical disease F06.9Unspecified mental disorder due to brain damage and dysfunction and to physical disease F07Personality and behavioural disorders due to brain disease, damage and dysfunction F07.0Organic personality disorder F07.1Postencephalitic syndrome F07.2Postconcussional syndrome F07.8Other organic personality and behavioural disorder due to brain disease, damage and dysfunction F07.9 Unspecified organic personality and behavioural disorders due to brain disease, damage and dysfunction F09Unspecified organic or symptomatic mental disorder - 44 - Introduction This block comprises`a range of mental disorders grouped together on the basis of their common, demonstrable etiology in cerebral disease, brain injury, or other insult leading to cerebral dysfunction. The dysfunction may be primary, as in diseases, injuries, and insults that affect the brain directly or with predilection; or secondary, as in systemic diseases and disorders that attack the brain only as one of the multiple organs or systems of the body involved. Alcohol- and drug-caused brain disorders, though logically belonging to this group, are classified under F10-F19 because of practical advantages in keeping all disorders due to psychoactive substance use in a single block. Although the spectrum of psychopathological manifestations of the conditions included here is broad, the essential features of the disorders form two main clusters. On the one hand, there are syndromes in which the invariable and most prominent features are either disturbances of cognitive functions, such as memory, intellect, and learning, or disturbances of the sensorium, such as disorders of consciousness and attention. On the other hand, there are syndromes of which the most conspicuous manifestations are in the areas of perception (hallucinations), thought contents (delusions), or mood and emotion (depression, elation, anxiety), or in the overall pattern of personality and behaviour, while cognitive or sensory dysfunction is minimal or difficult to ascertain. The latter group of disorders has less secure footing in this block than the former because it contains many disorders that are symptomatically similar to conditions classified in other blocks (F20-F29, F30-F39, F40-F49, F60-F69) and are known to occur without gross cerebral pathological change or dysfunction. However, the growing evidence that a variety of cerebral and systemic diseases are causally related to the occurrence of such syndromes provides sufficient justification for their inclusion here in a clinically oriented classification. The majority of the disorders in this block can, at least theoretically, have their onset at any age, except perhaps early childhood. In practice, most tend to start in adult life or old age. While some of these disorders are seemingly irreversible and progressive, others are transient or respond to currently available treatments. Use of the term "organic" does not imply that conditions elsewhere in this classification are "nonorganic" in the sense of having no cerebral substrate. In the present context, the term "organic" means simply that the syndrome so classified can be attributed to an independently diagnosable cerebral or systemic disease or disorder. The term "symptomatic" is used for those organic mental disorders in which cerebral involvement is secondary to a systemic extracerebral disease or disorder. It follows from the foregoing that, in the majority of cases, the recording of a diagnosis of any one of the disorders in this block will require the use of two codes: one for the psychopathological syndrome and another for the underlying disorder. The etiological code should be selected from the relevant chapter of the overall ICD-10 classification. Dementia - 45 - A general description of dementia is given here, to indicate the minimum requirement for the diagnosis of dementia of any type, and is followed by the criteria that govern the diagnosis of more specific types. Dementia is a syndrome due to disease of the brain, usually of a chronic or progressive nature, in which there is disturbance of multiple higher cortical functions, including memory, thinking, orientation, comprehension, calculation, learning capacity, language, and judgement. Consciousness is not clouded. Impairments of cognitive function are commonly accompanied, and occasionally preceded, by deterioration in emotional control, social behaviour, or motivation. This syndrome occurs in Alzheimer's disease, in cerebrovascular disease, and in other conditions primarily or secondarily affecting the brain. In assessing the presence or absence of a dementia, special care should be taken to avoid false-positive identification: motivational or emotional factors, particularly depression, in addition to motor slowness and general physical frailty, rather than loss of intellectual capacity, may account for failure to perform. Dementia produces an appreciable decline in intellectual functioning, and usually some interference with personal activities of daily living, such as washing, dressing, eating, personal hygiene, excretory and toilet activities. How such a decline manifests itself will depend largely on the social and cultural setting in which the patient lives. Changes in role performance, such as lowered ability to keep or find a job, should not be used as criteria of dementia because of the large cross-cultural differences that exist in what is appropriate, and because there may be frequent, externally imposed changes in the availability of work within a particular culture. If depressive symptoms are present but the criteria for depressive episode (F32.0- F32.3) are not fulfilled, they can be recorded by means of a fifth character. The presence of hallucinations or delusions may be treated similarly..x0 Without additional symptoms.x1 Other symptoms, predominantly delusional.x2 Other symptoms, predominantly hallucinatory.x3 Other symptoms, predominantly depressive.x4 Other mixed symptoms Diagnostic guidelines The primary requirement for diagnosis is evidence of a decline in both memory and thinking which is sufficient to impair personal activities of daily living, as described above. The impairment of memory typically affects the registration, storage, and retrieval of new information, but previously learned and familiar material may also be lost, particularly in the later stages. Dementia is more than dysmnesia: there is also impairment of thinking and of reasoning capacity, and a reduction in the flow of ideas. The processing of incoming information is impaired, in that the individual finds it increasingly difficult to attend to more than one stimulus at a time, such as taking part in a conversation with several persons, and to shift the focus of attention from one topic to another. If dementia is the sole diagnosis, evidence of clear consciousness is - 46 - required. However, a double diagnosis of delirium superimposed upon dementia is common (F05.1). The above symptoms and impairments should have been evident for at least 6 months for a confident clinical diagnosis of dementia to be made. Differential diagnosis. Consider: a depressive disorder (F30-F39), which may exhibit many of the features of an early dementia, especially memory impairment, slowed thinking, and lack of spontaneity; delirium (F05); mild or moderate mental retardation (F70-F71); states of subnormal cognitive functioning attributable to a severely impoverished social environment and limited education; iatrogenic mental disorders due to medication (F06.-). Dementia may follow any other organic mental disorder classified in this block, or coexist with some of them, notably delirium (see F05.1). F00 Dementia in Alzheimer's disease Alzheimer's disease is a primary degenerative cerebral disease of unknown etiology, with characteristic neuropathological and neurochemical features. It is usually insidious in onset and develops slowly but steadily over a period of years. This period can be as short as 2 or 3 years, but can occasionally be considerably longer. The onset can be in middle adult life or even earlier (Alzheimer's disease with early onset), but the incidence is higher in later life (Alzheimer's disease with late onset). In cases with onset before the age of 65-70, there is the likelihood of a family history of a similar dementia, a more rapid course, and prominence of features of temporal and parietal lobe damage, including dysphasia or dyspraxia. In cases with a later onset, the course tends to be slower and to be characterized by more general impairment of higher cortical functions. Patients with Down's syndrome are at high risk of developing Alzheimer's disease. There are characteristic changes in the brain: a marked reduction in the population of neurons, particularly in the hippocampus, substantia innominata, locus ceruleus, and temporoparietal and frontal cortex; appearance of neurofibrillary tangles made of paired helical filaments; neuritic (argentophil) plaques, which consist largely of amyloid and show a definite progression in their development (although plaques without amyloid are also known to exist); and granulovacuolar bodies. Neurochemical changes have also been found, including a marked reduction in the enzyme choline acetyltransferase, in acetylcholine itself, and in other neurotransmitters and neuromodulators. As originally described, the clinical features are accompanied by the above brain changes. However. it now appears that the two do not always progress in parallel: one may be indisputably present with only minimal evidence of the other. Nevertheless, the clinical features of Alzheimer's disease are such that it is often possible to make a presumptive diagnosis on clinical grounds alone. Dementia in Alzheimer's disease is at present irreversible. Diagnostic guidelines The following features are essential for a definite diagnosis: - 47 - (a) Presence of a dementia as described above. (b)Insidious onset with slow deterioration. While the onset usually seems difficult to pinpoint in time, realization by others that the defects exist may come suddenly. An apparent plateau may occur in the progression. (c)Absence of clinical evidence, or findings from special investigations, to suggest that the mental state may be due to other system

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