Langley and colleagues ^{Reference Langley, Fowler, Ford, Thapar, van den Bree and Harold1} reported 5-year follow-up outcomes of young children with attention-deficit hyperactivity disorder (ADHD) and the maternal and social factors related to the prognosis. The findings provide evidence of high comorbidity of antisocial behaviours associated with ADHD, drawing attention to the long-term outcomes of the disorder. Yet, in my opinion, additional information needs to be clarified regarding the findings.

The authors showed that medication use was not significantly associated with conduct disorder diagnosis or other antisocial behaviours. However, this interesting result was not discussed in detail in the article. What I am interested in is whether medication could reduce the risk of developing psychiatric diseases. Recently, studies have shown that treatment with stimulant drugs for ADHD could reduce the risk for some psychiatric disorders. In a systematic review, Wilens et al ^{Reference Wilens, Faraone, Biederman and Gunawardene2} reported that medication in childhood was associated with a reduction in the risk for subsequent substance misuse. Biederman et al ^{Reference Biederman, Monuteaux, Spencer, Wilens and Faraone3} showed that stimulant treatment of youths with ADHD decreased the risk for depressive and anxiety disorders and disruptive behaviour later in life. Both studies indicate that medication can benefit psychiatric outcomes. In Langley et al's study, ^{Reference Langley, Fowler, Ford, Thapar, van den Bree and Harold1} most of the participants (63%) received prescribed stimulant drugs, but the psychological outcomes were not optimistic regarding the prognosis of conduct disorder. Does this result suggest that medication is not beneficial for children with ADHD in the long term? What can account for it? In addition, why did children who were prescribed medication have more ADHD symptoms than those no longer using medication? ^{Reference Langley, Fowler, Ford, Thapar, van den Bree and Harold1}