This study followed 239 people who did not have ADHD in childhood. They had been classmates of children in a large ADHD study and were group-matched by sex. Researchers checked them eight times from about age 10 to about age 24. The group may include more males and slightly higher family income than the general population.
The team used a step-by-step process to test for late-onset ADHD. It weighed symptom counts, real-life problems, the age symptoms began, heavy substance use, and other mental health conditions. In adolescence, many first screened positive on symptom checklists (97 of 239). Only a small number passed every step of the process (6 of 239, or 2.5%). In adulthood, fewer still showed adult-onset ADHD that stood on its own (2 of 239, or 0.8%), and both met criteria at just one visit and had other mental health symptoms. Over half of the adolescents who met all the criteria were dropped because heavy substance use or another condition better explained their symptoms (53%). Among the adults who met all the criteria, most were dropped for the same reason (83%). The retained late-onset cases usually began in the teen years and faded.
The authors suggest clinicians assess impairment, psychiatric history, and substance use before diagnosing late-onset ADHD in this age group.
Source: Margaret H. Sibley, Luís Augusto Rohde, James M. Swanson, et al.. Late-Onset ADHD Reconsidered With Comprehensive Repeated Assessments Between Ages 10 and 25. American Journal of Psychiatry (2017). doi:10.1176/appi.ajp.2017.17030298