Attention-deficit–Hyperactivity Disorder Attention-deficit hyperactivity disorder (ADHD) is characterised by a triad of symptoms: inattention, hyperactivity and impulsivity.1 The disorder

Attention-deficit hyperactivity disorder (ADHD) is characterised by a triad of symptoms: inattention, hyperactivity and impulsivity.1 The disorder affects around 3–5% of school-age children, and symptoms often continue into adulthood, although severity lessens to some extent for most patients.2 Much research has been conducted aimed at the causal factors of the disorder. In short, genetic factors contribute more to increasing the risk of developing the disorder than environmental factors. About 75–80% of the variance can be explained by genetic factors,3 with multiple genes of small individual effect together increasing the risk of ADHD. Despite the fact that genetic factors are more important in relation to ADHD, certain environmental risk factors have also been identified as related to ADHD. Epilepsy, brain infections, complications during pregnancy and delivery, and exposure to alcohol, drugs and tobacco as a foetus are all more likely to have occurred in children who develop ADHD.4–6