Multivariate Analyses in Behavioural Genetics - Reading PDF

Multivariate Analyses in Behavioural Genetics - Reading 19 December 2023 14:37 Source Notes Schizophrenia genetics: emerging themes for a complex disorder (Kavanagh et al., 2015) Background Methods Results Schizophrenia, a complex psychiatric The review synthesizes findings from various genetic Comm...

Multivariate Analyses in Behavioural Genetics - Reading 19 December 2023 14:37 Source Notes Schizophrenia genetics: emerging themes for a complex disorder (Kavanagh et al., 2015) Background Methods Results Schizophrenia, a complex psychiatric The review synthesizes findings from various genetic Common Genetic Variation: GWAS studies disorder, has long been recognized to have studies, including GWAS and sequencing studies. identified over 100 common risk loci associated a genetic component. It covers research on common genetic variation with schizophrenia. These findings revealed Despite earlier challenges, recent through GWAS, investigation of rare genetic polygenic contributions, emphasizing the highly advancements in genetic technology, such variation via copy number variant (CNV) analysis, and polygenic nature of the disorder. as genome-wide association studies (GWAS) recent exome sequencing studies focusing on rare Rare Genetic Variation: CNV and sequencing single-nucleotide variants (SNVs) and small and sequencing, have provided valuable studies highlighted the role of rare variants, insights into the genetic architecture of insertions/deletions (indels). particularly in genes related to synaptic plasticity, schizophrenia. glutamate system disruption, and calcium signalling. The study aims to review these recent genomic findings and their implications for Overlap with Other Disorders: Evidence showed understanding the genetic basis of shared genetic risk among schizophrenia, bipolar disorder, autism spectrum disorders, major schizophrenia. depressive disorder, and attentiondeficit/hyperactivity disorder, indicating overlapping disease mechanisms. Strengths: The study represents a comprehensive review of recent advancements, amalgamating findings from various genetic studies, providing a holistic perspective on the genetic landscape of schizophrenia. Collaborative efforts among researchers enabled the analysis of large sample sizes, crucial for identifying both common and rare genetic contributors. Identification of common risk loci and rare variants associated with synaptic functions offers promising directions for understanding the biological mechanisms underlying schizophrenia. Limitations: Challenges in pinpointing specific functional variants for most findings underscore the need for richer annotation data to enhance biological understanding. The study's focus on specific gene sets and regions limits the exploration of broader biological processes potentially implicated in schizophrenia. The complexity of genetic contributions poses challenges for precise mechanistic understanding and translation of findings into clinical applications. Implications for the Field: The findings emphasize the need for larger sample sizes and enhanced genomic resources to elucidate the full spectrum of genetic contributions to schizophrenia. Shared genetic risk among psychiatric disorders underscores the importance of considering overlapping disease mechanisms for more effective research and clinical approaches. Identified biological pathways related to synaptic functions and neural signalling pathways offer potential targets for future research aiming at better understanding the disorder and developing new treatments. Evidence for substantial genetic risk for psychopathy in 7 -year-olds Background Method Results (Viding et al., 2005) The study investigates the heritability and environmental influences on callous-unemotional traits (CU) and antisocial behavior (AB) in children aged 7 years, focusing on their potential role in predicting later life-course persistent antisocial behavior. CU traits, characterized by lack of guilt, empathy, and emotional shallowness, are linked with psychopathy and often co-occur with AB. Understanding the genetic and environmental factors behind these traits in childhood can inform prevention and treatment strategies for severe antisocial behavior. Participants: 7374 twins from the 1994-1995 birth cohorts were part of the Twins Early Development Study (TEDS). Teacher assessments were collected for 3487 pairs at 7 years old. CU Traits: Extreme CU at age 7 Strengths: The study provides insights into the genetic and showed strong genetic influence (h2g environmental underpinnings of CU and AB in children, highlighting = 0.67) and minimal shared the significant role of genetics in these traits. Limitations: Data collected at a single age, reliance on teacher environment (c2g = 0.06). AB with Psychopathic Tendencies: reported measures, and a non-standard CU scale might limit Extreme AB in children with generalizability. Future research may benefit from longitudinal psychopathic tendencies (AB/CU+) assessments and additional measurement sources. exhibited high heritability (h2g = 0.81) Implications: Findings suggest that genetic vulnerability strongly and negligible shared environment influences CU and AB in children, emphasizing the need for (c2g = -0.05). targeted interventions focusing on these traits. The study AB without Psychopathic Traits: underscores the importance of early prevention strategies, molecular genetics research, and brain-behavior studies in Extreme AB in children lacking psychopathic traits (AB/CU-) displayed understanding and treating severe antisocial behavior. modest heritability (h2g = 0.30) and moderate shared environment (c2g = 0.34). The severity of AB did not affect heritability estimates, indicating that CU traits largely accounted for the higher heritability seen in children with psychopathic tendencies. Developmentally dynamic genome: Evidence of genetic influences on increases and decreases in conduct problems from early childhood to adolescence (Pingault et al., 2015) Generalist Genes and Learning Disabilities (Plomin and Kovas, 2005) Measures: Teachers rated CU and AB using a scale derived from the Strengths and Difficulties Questionnaire (SDQ) and Antisocial Process Screening Device items. Analyses: The study used twin analyses to estimate group heritability (h2g) and shared environment (c2g) for extreme CU and AB, distinguishing children with and without psychopathic tendencies. Introduction: Participants: Genetic and Environmental The study aimed to explore the genetic The study involved 10,038 twin pairs Contributions: and environmental influences on the from the Twins Early Development Genetic factors consistently developmental course versus the baseline Study (TEDS) with conduct problem influenced conduct level of conduct problems from early assessments between ages 4 and 16. problems across ages, childhood to adolescence. showing genetic continuity. Conduct problems in childhood and Measures: Substantial genetic adolescence are linked to adverse long Conduct problems were assessed innovation was observed, term outcomes like increased mortality, using the Strength and Difficulty with new genetic influences psychiatric morbidity, and criminality. Questionnaire (SDQ), completed by emerging over time. Understanding individual differences in Shared environmental parents at ages 4, 7, 12, and 16 the development of conduct problems is years. influences were small and crucial. did not significantly Statistical Analysis: contribute to long-term changes. Previous Studies: The study employed Cholesky Previous meta-analyses and longitudinal decomposition to analyse genetic Latent Growth Curve Model: studies have highlighted moderate to high and environmental influences at heritability estimates for antisocial different ages and used a latent Conduct problems showed a growth curve model (LGC) to assess behavior and conduct problems. significant linear decrease the developmental course of Longitudinal research showed genetic from age 4 to 16. conduct problems. continuity but also the emergence of new Both baseline levels and genetic factors contributing to changes in developmental courses were behavior over time. strongly influenced by genetic factors. Research Gap: Genetic factors specific to Existing longitudinal studies the developmental course demonstrated genetic influences on agewere largely independent of to-age change but didn't directly address those influencing the baseline level. the role of genes in the developmental course of conduct problems—systematic changes occurring with age, like linear Complementary Analyses: increases or decreases. Removing aggression from This study aimed to bridge this gap using a conduct problem measures large twin sample followed from early slightly altered the decline childhood to adolescence. pattern but didn't significantly affect genetic and environmental influences. Critical analysis Strengths: Large and representative sample size. ○ This allows for more reliable and conclusive inferences about the role of genetic and environmental influences on the developmental course of conduct problems. Longitudinal design capturing developmental changes. ○ longitudinal approach provides a more comprehensive understanding of the developmental trajectory of conduct problems and their underlying influences Limitations: Low internal consistency in conduct problem measures. ○ reliance on parent reports of conduct problems may introduce measurement error due to potential discrepancies between parent perceptions and children's actual behavior Reliance on parent reports instead of self-reports. ○ finding of non-significant shared environmental influences on the developmental course of conduct problems suggests that interventions targeting shared environmental factors may have limited effectiveness. However, the study's reliance on parent reports may have underestimated the influence of shared environmental factors, which could be further explored using more objective measures Non-significant shared environmental influences on the developmental course might limit intervention strategies focused on shared environmental factors. Significance: The study shows that genetic factors play a significant role in both the baseline level and the developmental course of conduct problems. This highlights the importance of considering genetic influences in interventions and research targeting conduct problems. Future Directions: Need for integrated models considering genetic influences on behavior development. Importance of distinguishing between genetic and environmental predictors in intervention studies for conduct problems. Calls for repeated interventions at different developmental stages for long-term impact. Background: The study focuses on genetic research in psychology, particularly on the genetic links within and between learning disabilities, such as language, reading, and mathematics disabilities. The research aims to review the genetic links between learning disabilities and abilities, genetic homogeneity within learning disabilities, and genetic comorbidity between learning disabilities and abilities. The study assumes a background in quantitative genetics and emphasizes the importance of genetic findings in understanding learning disabilities. Methods: The study uses multivariate genetic analyses, such as the DeFries-Fulker (DF) extremes analysis and Cholesky path model, to assess genetic links between learning disabilities and abilities. It also conducts bivariate and trivariate genetic analyses to examine genetic homogeneity and comorbidity across different learning disabilities. The research utilizes twin studies, including the Twins Early Development Study (TEDS), to investigate genetic correlations and heritability estimates for language, reading, and mathematics disabilities and abilities. Results: The findings indicate substantial genetic links between learning disabilities and abilities, suggesting that learning disabilities are the quantitative extreme of the same genetic influences that contribute to the normal range of learning abilities. The study also reveals strong genetic homogeneity within learning disabilities, with substantial genetic correlations found for language, reading, and mathematics components. Additionally, the research demonstrates strong genetic comorbidity between language and reading, as well as between language and mathematics, indicating significant genetic overlap between different learning disabilities. PSYC0036 Genes and Behaviour Page 1 different learning disabilities. Critical Analysis: The study's strengths lie in its comprehensive use of multivariate genetic analyses and twin studies to provide robust evidence for genetic links within and between learning disabilities. The findings contribute to the field by challenging the traditional notion of distinct genetic bases for disabilities and highlighting the importance of genetic research in understanding the genetic underpinnings of learning disabilities. However, the study also acknowledges limitations, such as the need for further research to test the hypothesis of genetic homogeneity and comorbidity across different components of learning disabilities. Additionally, the study emphasizes the importance of considering environmental factors and the interplay between nature and nurture in the development of learning disabilities. Overall, the research provides valuable insights into the genetic basis of common learning disabilities and their overlap with normal learning abilities, but further research is needed to confirm and expand upon these findings. Genetic Heterogeneity Between the Three Components of the Autism Spectrum: A Twin Study (Ronald et al., 2005) Background: The study aimed to explore the influence of genetics and environment on autistic-like traits, using a community sample of 8-year-olds, focusing on the Childhood Asperger Syndrome Test (CAST) as a measurement tool. It sought to understand the genetic heterogeneity of various components of autism spectrum disorders (ASDs) – social impairments (SIs), communication impairments (CIs), and restricted, repetitive behaviors and interests (RRBIs) – and their genetic and environmental influences. The research was derived from twin studies and family analyses in the field of autism research. Methods: Participants: Utilized a subset of the Twins Early Development Study (TEDS) comprising 3,419 pairs of 8-year-old twins. Measure: Employed the CAST, a 31-item screening instrument for ASDs, categorized into SIs, CIs, and RRBIs based on DSM-IV criteria. Analyses: Conducted various statistical methodologies including heritability estimation, probandwise concordances, liability threshold modeling, and DeFries-Fulker extremes analysis, along with twin correlations and multivariate genetic analysis. Results: Heritability: High heritability, limited shared environment, and moderate nonshared environment were observed for autistic-like traits across the spectrum. Extreme Traits: Extreme autistic-like traits showed similar genetic influences to traits across the spectrum. Genetic Heterogeneity: SIs, CIs, and RRBIs exhibited genetic heterogeneity with minimal shared genetic influences between the components. Gender Differences: Minor gender differences were found, suggesting X-linked genetic influences on autistic-like traits. Phenotypic Correlations: The three components showed moderate correlations, indicating distinct genetic origins for each component. Limitations: The study relied on parent reports, had attrition bias, and minor missing data. Additionally, the CAST's low internal consistency cautioned interpretation. Critical Analysis: Strengths: ○ Sample Size: Large community-based sample size provided robust statistical power. ○ Analytical Depth: Employed various statistical methods to assess genetic and environmental influences comprehensively. ○ Continuum to Extreme Analysis: Investigated the relationship between extreme traits and the broader spectrum of autistic -like traits. Limitations: ○ Reliance on Parent Reports: Potential biases and subjective interpretations in reporting autistic-like traits. ○ Measurement Tool Reliability: The CAST's low internal consistency raises concerns about subscale interpretations. ○ Missing Data and Attrition Bias: Could impact the study's generalizability and robustness of conclusions. Contributions to the Field: ○ The study's findings suggest genetic heterogeneity among different components of ASDs, emphasizing the need for molecular gen etics research to identify specific genes associated with each component. ○ The continuum-to-extreme relationship warrants further exploration, especially through molecular genetic studies to validate the relationship between extreme traits and clinical ASD diagnoses. All for One and One for All: Mental Disorders in One Dimension (Caspi and Moffitt, 2018) Background: The study explores the concept of a single dimension, termed "p," which measures a person’s liability to mental disorder, comorbidity among disorders, persistence of disorders over time, and severity of symptoms. It discusses the potential implications of this dimension in biological psychiatry, treatment, and prevention of mental disorders. The study also emphasizes the need for further research to develop reliable measures for "p" and explore its potential implications in various aspects of psychiatric disorders. Methods: The study utilizes a combination of cross-sectional and longitudinal data, as well as statistical analyses such as network analysis and bifactor modeling to investigate the correlations among psychiatric symptoms and disorders. It also incorporates external validation to test the response style hypothesis and explores various hypotheses regarding the substantive meaning of the "p" factor, including neuroticism, emotional dysregulation, and intellectual impairments. Results: The study finds that there is a potential single underlying factor, "p," that summarizes individuals’ propensity to develop any and all forms of common psychopathologies. It suggests that this factor may represent a diffuse unpleasant affective state, poor impulse control over emotions, and deficits in intellectual function. The study also highlights the potential for "p" to enhance discovery in biological psychiatry and encourages the development and experimentation with transdiagnostic treatments. Critical Analysis: Strengths of the study include its comprehensive review of existing literature, the use of both cross-sectional and longitudinal data, and the exploration of multiple hypotheses regarding the substantive meaning of the "p" factor. However, the study also has limitations, such as the need for further validation of the "p" factor and the potential for publication bias in the transdiagnostic studies. The findings contribute to the field by highlighting the potential for a unified approach to understanding and treating psychiatric disorders, but further research is needed to fully validate and understand the implications of the "p" factor. PSYC0036 Genes and Behaviour Page 2