Many children and adults with AD/HD also experience other difficulties. It seems that having AD/HD makes it more likely that an individual will also have other difficulties. If a child meets criteria for AD/HD, it may not be enough to prescribe a stimulant get a few checklists and do follow up twice a year.
There has been increasing awareness that many adults and children with AD/HD may also meet criteria for one or more other psychiatric diagnoses. (Comorbidity means having two or more diagnosable conditions at the same time) There is some evidence that the incidence of comorbidity is somewhat higher in adults than in children.
However, many of the studies looking at the issue of comorbidity are difficult to compare. Studies used different criteria for AD/HD and bipolar disorder, and sometimes got their subjects from different populations. For example, one might expect to see more complex types of AD/HD in specialized hospital clinics than one would see in a door-to-door survey or in a primary care physician’s office. Despite the differing criteria across studies, and the lack of large general population studies of adult AD/HD, there is still convincing data that several other psychiatric diagnoses are common among children and adults with AD/HD.