Late-Onset Attention-Deficit/Hyperactivity Disorder: Do the Findings ADD Up?

A diagnosis of attention-deficit/hyperactivity disorder (ADHD) requires symptom onset by age 12. To examine support for this requirement, two research groups conducted longitudinal studies of birth cohorts in Brazil (N=5249) and in the U.K. (N=2040). Both studies used repeated assessments with DSM-IV screening instruments in childhood (at age 11 in the Brazil study and at multiple ages in the U.K. study) and interviews using DSM-5 criteria (other than age) at age 18 or 19.

Of the Brazilian cohort, 9% had ADHD at age 11 (childhood ADHD [C-ADHD]), and 12% had this diagnosis at age 18 or 19 (young adult [YA-ADHD]), about half of whom had no comorbidities. The rate of persistence of C-ADHD into YA-ADHD was 17%, whereas 13% of YA-ADHD patients ha…