In addition to leave-one-out analyses, we also explored whether moderators were associated with heterogeneous effect sizes in the 4 substance outcomes identified above. We tested each coded moderator separately using the metareg command for simple regressions. Two moderator variables predicted heterogeneity in effect size in alcohol abuse or dependence. The percentage of children with ADHD treated with stimulant medication (number who received medication/total number of children with ADHD) was negatively associated with pooled effect size (t = −4.25, P =.003, adjusted R2 = 89.05). As the proportion of those with ADHD who received stimulant medication increased, the OR decreased significantly. In other words, studies with a smaller proportion of individuals treated with stimulant medication were more likely to have those youth meet diagnostic criteria for alcohol abuse or dependence. In addition, as the number of years between initial assessment and the substance use follow-up assessment increased, ORs were larger (t = −4.25, P =.003, adjusted R2 = 28.91). That is, increased rates of alcohol abuse or dependence were observed for youth treated with medication with longer follow-up. When both moderators
