Although AttentionDeficit Hyperactivity Disorder (ADHD) has traditionally been thought of as a childhood condition there is evidence that in a high proportion of cases it carries on into adulthood. ADHD in adulthood can be a serious risk factor for a number of other mental-health problems such as antisocial personality disorder, substance misuse and depression and is also linked to a lower level of education and higher levels of unemployment, divorce, criminality and road-traffic accidents. A review of studies into adult ADHD found that its prevalence was around 2.5%. Younger people and men were most likely to show symptoms of the condition which declined in prevalence with age.
Simon, Viktoria ... [et al] - Prevalence and correlates of adult attention-deficit hyperactivity disorder: meta-analysis British Journal of Psychiatry March 2009, 194(3), 204-211