ADHD

Attention-Deficit Hyperactivity Disorder (ADHD)

• ADHD is a neurodevelopmental disorder characterized by inattention, impulsiveness, and hyperactivity.
• Core symptoms include problems with attention, impulsivity, and hyperactivity.
• ADHD presents in two main domains: inattention and hyperactivity/impulsivity.
• Three presentations exist: inattentive, hyperactive/impulsive, and combined type.
• Inattention symptoms in adults (at least 5/9): failing to pay attention to details, difficulty concentrating, not seeming to listen, not following instructions, difficulty organizing tasks, avoiding tasks requiring effort, easily distracted, forgetfulness.
• Hyperactivity/Impulsivity symptoms in adults (at least 5/9): fidgeting, inability to stay seated, feeling restless, talking excessively, difficulty awaiting turn, interrupting others.
• ADHD often persists into adolescence and adulthood with often different symptoms.
• Prevalence in children is 4-6%, and in adults 2-3%.
• The male-to-female ratio in childhood/adolescence is approximately 2.5:1.

Outline of Presentation

• Clinical presentation of ADHD
• Catecholaminergic neurotransmission (a recap)
• Catecholaminergic dysfunction in ADHD
• Management of ADHD
• Stimulant mechanisms of action
• Stimulant effects on the brain
• Non-stimulant medication
• Predicting treatment response

Prevalence and Demographic Differences

• Prevalence of ADHD is similar across different socioeconomic regions (LMIC and HIC).
• No significant differences observed in prevalence between LMIC and HIC regions.
• 4-6% of children exhibit ADHD, whereas 2-3% of adults show ADHD symptoms.
• 2.5 to 1 male-to-female ratio in children and adolescents (referral bias).
• ADHD persists in adolescence (50-80%) and adulthood (30-50%), but the symptoms may change.

Adult Life

• Symptoms of ADHD usually decline with age.
• Functional impairment associated with ADHD decreases over time.
• Approximately 15% of diagnosed ADHD cases persist with full diagnostic criteria in adulthood.

Clinical Cases

• Presented with detailed examples of case studies, which included various ages and presentations of ADHD.

ADHD and Everyday Life

• ADHD is associated with negative outcomes, including:
• Academic problems
• Employment problems
• Risk-taking behaviours
• Addictions
• Health problems (obesity, etc.)
• Emotional and conduct problems (bullying, criminal behaviours)
• Teen pregnancies

Diagnosis of ADHD

• Requires observable symptoms in multiple settings (e.g., home, school, etc.) for at least six months.
• Symptoms emerge primarily during early to mid-childhood.
• No single biological marker exists.
• Psychologists use a combination of psychiatric interviews & collateral information (e.g., school reports)
• Rating scales and neuropsychological test results support the clinical assessments.

Etiology of ADHD

• The liability threshold model suggests both genetic and environmental factors determine ADHD.
• Neither factor alone is sufficient to cause ADHD; accumulation of risk factors leads to symptom manifestation.
• Genetic factors include polygenic risk, familiarity, and a p-factor.
• Environmental factors include toxins (including alcohol and nicotine exposure during pregnancy), nutritional deficiencies, obstetric complications, low birth weight, premature birth, maternal hypertension, obesity, stress levels, and infections.

Neurobiology of ADHD

• ADHD correlates with structural and functional differences that are primarily present in the fronto-striatal networks (and also the parietal and cerebellar regions).
• These areas play key roles in functions like attention, inhibition, motivation, and emotion.
• Catecholaminergic pathways (dopamine and norepinephrine) are essential in these brain processes.

Catecholaminergic pathways

• Dopamine and norepinephrine are key neurotransmitters impacted in ADHD.
• Activity within these networks is modulated by dopamine (DA) and norepinephrine (NE).
• The areas in which these neurotransmitters are released have a direct impact on functions such as concentration and attention.

Cortico-striatal loops

• These loops consist of GABAergic and glutamatergic circuits.
• These pathways are modulated by dopamine.
• Involved in motor planning, cognitive functions, and emotional processing.
• Function disruption can explain the symptoms of ADHD.

Stimulant effects on brain regional structure and function

• Early MRI studies show that stimulant treatment can attenuate or eliminate early grey matter differences in ADHD.
• Further studies on chronic treatment showed inconsistent results, showing no conclusive evidence for longer-term brain functional improvement.

Stimulant effects on brain structural and functional connectivity

• Emerging evidence suggests stimulant treatments influence brain activity and connectivity patterns.
• Stimulant treatments can enhance connectivity of task-related brain regions and reduce connectivity of default mode brain networks.

Non-stimulants

• Atomoxetine is a selective norepinephrine reuptake inhibitor.
• It reduces NE reuptake (primarily in the prefrontal cortex).
• Guanfacine is selective alpha-2A receptor agonist. It modulates norepinephrine effects within the prefrontal cortex.

Predictors of Treatment Response

• Neuroimaging studies try to identify biological predictors of treatment response in adults with ADHD
• Using different types of neuroimaging (MRI, fMRI, PET, and others) helps identify specific brain structures or functions that might predict who responds well to treatment or not in adults with ADHD. Brain connectivity patterns can predict treatment response.

Management of ADHD (NICE Guidelines)

• Pre-schoolers (< 5 years): ADHD-focused parent training programs are an initial step. Consider medication if symptoms persist across multiple domains.
• Children and adolescents (≥ 5): Consider medication, such as methylphenidate, lisdexamfetamine, or atomoxetine/guanfacine if symptoms persist across multiple domains. Consider additional support if symptoms related to Oppositional Defiant Disorder or Conduct Disorder co-occur.
• Adults: Consider medication (methylphenidate, lisdexamfetamine or dexamphetamine, atomoxetine) in order; Consider supportive psychological interventions if medication is ineffective.

Indication for ADHD meds

• Stimulants (methylphenidate, Ritalin, Concerta) are often first-line treatment for moderate to severe impairment.
• Other options (lisdexamfetamine, atomoxetine, guanfacine) might also be considered.

Cautions/Side Effects of ADHD medication

• Stimulant medication may increase blood pressure and heart rate.
• Stimulants can sometimes impact appetite and sleep patterns.
• Regular monitoring of blood pressure, heart rate, height, and weight during treatment is appropriate.

Different formulations of Methylphenidate Medication

• Different formulations exist for methylphenidate, offering variable release patterns. This helps maintain optimal medication levels throughout the day. 

MPH vs Amphetamines

• Methylphenidate and amphetamines (and their derivatives) are both stimulants.
• D-enantiomer of methylphenidate is responsible for most effects (unlike amphetamines).
• Methylphenidate directly and indirectly affects the release of dopamine and/or norepinephrine in the brain.

Test your knowledge about Attention Deficit Hyperactivity Disorder (ADHD) focusing on its symptoms, prevalence, and treatment options. From common symptoms in children to management strategies for adults, this quiz covers the key aspects of ADHD. Perfect for students and professionals looking to enhance their understanding of this condition.