The causes of ADHD are complex and multifactorial, with genetics, early environment and gene-environment interplay all being involved. No single risk factor is either necessary or sufficient to explain its occurrence. ADHD is highly heritable, and multiple types of genetic variants appear to be involved. None are diagnostic. Early environmental factors (e.g. diet, pre-and perinatal factors, toxins and psychosocial risks) have also been extensively investigated but whilst correlations have been

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... ound between many environmental influences and ADHD, it is difficult to prove definite causes. Later, potentially modifiable factors might influence its course and outcomes and more research is needed on this. Clinical assessment should be detailed and go beyond asking about diagnostic items. There are specific guidelines for the stepwise management of ADHD, and when following these, the severity of symptoms and an individual's circumstances and medical history should be taken into account. If ADHD medications are prescribed, it should be in conjunction with behavioural interventions. ADHD medication needs to be regularly reviewed. ADHD in many respects behaves like a chronic medical disorder. For many individuals, multimodal interventions that are carefully adjusted over time will be important. A developmental approach to assessment and treatment is necessary, taking into account how presentation and risks change over time.