Investigators have previously contended40,41 that the putative protective effect of stimulant medication in the original study by Biederman et al42 may have instead revealed age-related differences given that older participants simply have greater opportunity to have ever tried substances or to have ever met criteria for substance abuse or dependence. Furthermore, in the more recent study by Biederman et al,13 hazard ratio CIs included 1 for lifetime alcohol abuse and dependence, drug abuse and dependence, and nicotine dependence at a 10-year follow-up based on stimulant medication treatment status. Age at follow-up remains an important consideration for substance use outcomes because substance patterns may continue to change as individuals enter middle and older adulthood.
