Discussion
We have previously reported that children with ADHD prospectively followed through adulthood have deficits in multiple domains, relative to non-ADHD peers3 . However, outcomes vary substantially, warranting investigation of their early precursors. This study was designed to explain variation in functional outcomes of ADHD among children followed through adulthood (at mean age 41), when participants had reached functional independence. A summary of our findings is presented in Table 5. Contrary to expectations, we identified very few factors that contributed meaningfully to multiple aspects of adult outcome. This finding is congruent with the extant literature on adult outcome of children with ADHD6,11-13,31,32, which, with the exception of severity of ADHD and comorbid conduct disorder31,32, has not been able to identify many common predictors of later outcome. In terms of the variety of outcomes predicted, childhood IQ emerged as the most meaningful contributor. It was positively associated with higher educational attainment, occupational ranking, occupational functioning, and social functioning. This relationship is striking insofar as we excluded children with IQ’s below 85, indicating the contribution of IQ even within the average range of intellectual functioning. Evidence for the relationship between IQ and functional outcomes has been less equivocal (although significant associations are not always found) than its influence on other outcomes6,11,13,31,32. For example, in the Multimodal Treatment Study of Children with ADHD (MTA), IQ was predictive of several aspects of young adult functioning11, but it was not found to be a meaningful predictor of persistence of ADHD into adulthood33. It is likely that different characteristics in childhood are relevant for different aspects of adult outcome. Two other features, parental socioeconomic status and child reading level, both correlated with IQ, were also associated with higher educational attainment.
