We tested whether potentially important demographic and methodologic factors across the studies moderated the association between stimulant treatment and later substance use and abuse or dependence when heterogeneous effect sizes were detected. The following demographic characteristics were coded: (1) mean age of the sample at follow-up (in years), (2) sex composition (percentage male), (3) racial diversity (percentage white), and (4) mean age of initial ADHD assessment. Methodologic characteristics of each study were coded as follows: (1) percentage of participants with ADHD in the medicated group, (2) sample source (ie, clinic referred vs other), (3) DSM version used to determine ADHD status (ie, DSM-III, DSM-III-R, or DSM-IV), and (4) the mean number of years between the initial assessment and follow-up. Although symptom severity has been associated with substance outcomes,20 we were unable to include it in any moderator analyses because only 3 studies reported severity of baseline ADHD separately for stimulant· treated youth with untreated youth with ADHD.
