Attention-Deficit/Hyperactivity Disorder (ADHD) is a common childhood behavioural disorder – systematic reviews indicate that the community prevalence of ADHD globally is between 2% to 7%, with an average of around 5%. In addition, a further 5% of children have significant difficulties with over-activity, inattention and impulsivity that are just sub-threshold to meet full diagnostic criteria for ADHD. Estimates of the administrative (clinically diagnosed and/or recorded) prevalence vary worldwide and although increasing over time, ADHD is still relatively under-recognised and under-diagnosed in most countries, particularly in girls and older children. ADHD often persists into adulthood and is a risk factor for other mental health disorders...