ADHD has a strong genetic clustering (80%) but its etiology is still in question. The current requirement that all of the symptoms must be manifested by seven years of age will probably be dropped in future diagnostic criteria.15
Once it was thought that ADHD disappeared in adolescence but what we were really seeing was the transformation of the most visible feature of hyperactivity, calm into mere restlessness. The degree to which ADHD “persists” depends upon the criteria that are used to define persistence. About 35% of children who met full DSM criteria in childhood continue to meet full criteria as adults. If you lower the cut off to just five out of nine symptoms instead of six, the persistence rates jump to 65%. If you define persistence as having met criteria in childhood and still having areas of significant impairment as an adult, the persistence rate reaches 85%.17
The disorder is manifested as a persistent pattern of inattention/easy distractibility and/or hyperactivity-impulsivity that is significantly more severe than that observed in persons of a comparable level of development. This inattention and/or impulsivity interferes significantly in all areas of function (school, work, social/family relationships, mood regulation, and self-esteem).
Historic estimates for prevalence are 3 to 5 percent of the population but only the hyperactive or “disruptive” child was identified and the “silent” or inattentive child was missed. Two recent nearly identical prospective studies give clearer estimates:
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