ratio (OR) = 0.95, Wald w 2 = 13.78, P50.001). Verma et al are concerned that we excluded patients with shorter treatment durations. However, when we include all individuals who ever used stimulants, we find the same effect (OR = 0.95, Wald w 2 = 11.89, P = 0.001). Purely for illustrative purposes, we plotted the predicted probability of substance use disorder for the control group in Fig. 1. The figure shows that delay in the first age at stimulant use leads to marked increases in the probability of developing substance use disorder. In our article, we examined whether the effect of stimulant treatment depended on other factors (i.e. current use of stimulants, age at stimulant treatment initiation, age-adjusted duration of stimulant use and ageadjusted cumulative dosage), but found no other significant predictors than age at first stimulant use. Verma and colleagues refer to a meta-analysis, but provide the wrong citation. Recently, a meta-analysis on this topic was published. 2 Here no difference was found between treated and untreated patients in risk of developing substance use disorder (including alcohol, marijuana, cocaine and non-specific drugs) and nicotine use. Unfortunately, in this meta-analysis specific moderator variables such as age at first stimulant use were not taken into account, probably because of the relatively low numbers of studies to date that include such variables. We thank the authors for discovering the mistake in the table, 9% should have read 59%.