Stimulant medication is frequently and effectively used to treat attention-deficit/hyperactivity disorder (ADHD). Given the large number of patients currently being treated with stimulants, concerns have been raised about the possibility that use of stimulants could predispose these children to substance abuse in adolescence and young adulthood. Barkley and colleagues designed a longitudinal study focusing on the way stimulant use in childhood affects substance abuse and dependence in later life. Their study differs from previous studies in that it also controls for the current severity of ADHD and the lifetime severity of conduct disorder in determining this risk.

The study followed a group of 158 children strictly diagnosed with ADHD, as well as 81 matched community control subjects, for approximately 13 years. Participants were evaluated at baseline (ages four to 12 years), and again at ages 12 to 20 years, and at 19 to 25 years. Evaluation included parent and patient interviews, psychologic testing, and rating scales. The study focused on children who had ever been treated with stimulants and those who had not.

At adolescent follow-up, no significant difference was seen regarding substance abuse between children who had been treated with stimulants and those who had not. At adult follow-up, the two groups did not differ significantly in most measures of drug use, but a marginally significant increase in cocaine use was found among treated children. However, after controlling for conduct disorder, this difference disappeared. Lifetime conduct disorder symptoms did contribute significantly to increased cocaine use. The authors repeated the analysis for the hyperactive probands who had or had not been treated with stimulants in high school. These findings were similar to those of the adult follow-up.

The authors conclude that treating children and adolescents who have ADHD with stimulants does not increase their risk of substance abuse in adolescence and adulthood. This finding is consistent with the results of most previous studies. The increased risk of cocaine use in treated children disappears when controlling for severity of current conduct disorder symptoms.