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 disorder, 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)