Attention Deficit Hyperactivity Disorder (ADHD)

Persistent pattern of inattention and/or hyperactivity-impulsivity that is more frequent and severe than is typically observed in individuals at a comparable level of development and which interferes with functioning and/or development

Aetiology

• Present in about 4-5% of children

• Genetic predisposition + perinatal precipitants + psychosocial adversity → neuroanatomical brain changes → cognitive and behavioural features of ADHD

Genetic factors

• Mainly dopamine and serotonin transporter genes involved

Perinatal factors

• Alcohol and tobacco use during pregnancy

• Significant prematurity and perinatal hypoxia

• Other complications include unusually short or long labour, foetal distress, low forceps delivery and eclampsia

• Some evidence suggests an association with exposure to viral infection in first trimester

Psychosocial adversity

• There are some weak links between particular parenting styles and an increase of ADHD - in particular inconsistent parenting

• Severe marital discord, lower social class, large family size, paternal criminality, maternal mental disoder, maltreatment and emotional trauma have all been associated with higher rates of ADHD

• BUT the relationship between causation and simple association cannot really be established

Pathophysiology

Neurobiology of ADHD

• The typical brainmap pattern seen in children with ADHD shows an underactive function within the frontal lobe
• Frontal lobe is mainly responsible for reasoning, planning, impulse control etc.

Neurochemistry of ADHD

• There seems to be an excessively efficient dopamine-removal system (higher concentration of dopamine transporters - re-uptake inhibitors)

• Symptoms may also be caused by the reduction of norepinephrine (can affect attention when acting as stress hormone); and serotonin (which influences mood, social behaviour, sleep, and memory)

Impact of childhood ADHD

• Significant difficulties parenting children with ADHD

• Increased level of home stress and high expressed emotions

• Emotional dysregulation leads to difficulties in peer relationships and reckless and dangerous behavior

• Poor problem solving ability leading to developmentally inappropriate decision making

• Significant barrier to learning and potentially exlusion from education

• Higher likelihood of antisocial behaviours

Impact of adult ADHD

• There is an increase in the frequency of psychiatric comorbidity as compared to children

• Higher levels of criminality, antisocial behaviour

• Higher level of substance misuse - link to self-medication?

• Significant impairments in occupational function that could easily be accommodated for if diagnosis known

• Most adults will still present with residual symptoms but will no longer meet diagnostic criteria
• Possibly because there is an improvement in cortical thickness (maturation) that allows for the brain to compensate for cognitive deficits

Clinical presentation

• Triad of inattention, hyperactivity, and impulsivity

• Frequently co-occuring with a cluster of impairing symptoms relating to self-regulation (i.e. executive functioning, emotional regulation)

• These symptoms are: developmentally inappropriate, impairing functioning, pervasive across settings, and longstanding from age 5

Investigations

• ADHD is a spectrum disorder - cut off is clinically determined, aided by screening and assessment tools generally based on level of impairment
• Can be subjective which can be controversial due to different thresholds for diagnosis

Assessment in childhood

• Mainly driven by parents/school

• Ideal assessment is a school observation

• Screening questionnaires and structured diagnostic questionnaires are helpful

• Background information regarding risk factors, including developmental history and family history

• Exploration of early history and attachment styles

• 6 or more symptoms of inattentiveness; and/or

• 6 or more symptoms of hyperactivity and impulsiveness

• Present before 5 years

• Reported by parents, school, and seen in clinic

• Symptoms get in the way of daily life

Assessment in adulthood

• Driven by the patient

• Historical concerns by parents/siblings/relatives

• Specific adult screening toolds are avaliable

• Current clinical picture should be consistent with ADHD (not just historical difficulties)

• Cognitive difficulties and ability to function need to be evaluated

• Comorbidities are much more common

• There is disagreement about whether symptoms used to diagnose children also apply

• In general, 5 or more of the symptoms of inattentiveness; and/or

• 5 or more of hyperactivity and impulsiveness

• Historical concerns since early age

• For adults it is essential for the diagnosis that symptoms should have a moderate effect on different areas of their life, such as:
• Underachieving at work or in education
• Driving dangerously
• Difficulty making or keeping friends
• Difficulty in relationships with partners

Management

• Medical treatment is key in moderate to severe cases but needs to be accompanied by social, educational and parenting interventions

Psychosocial interventions for mild, moderate, and severe ADHD in children

• Parent training

• Social skills training

• Sleep and diet (controversial)

• Behavioural classroom management strategies

• Specific educational interventions

Pharmacological only for moderate-severe ADHD

• Methyphenidate - increases dopamine by blocking its transporter

• Dexafetamine - as above but also increases extracellular norepinephrine and possibly serotonin

• Lisdexafetamine

• Atomoxetine - increases norepinephrine by blocking its transporter

• Clonidine - increases norepinephrine by reducing sympathetic stimulation

• Guanfacine - as above