Authors' reply

In response to Tyrie & Knibbs, positive accounts of improvement and recovery from any disorder or difficulties are important and inspiring, but they cannot be taken as evidence for the efficacy of a particular treatment. The efficacy of treatments can only be established by randomised controlled trials, and these demonstrate that people taking stimulants for adult attention-deficit hyperactivity disorder do only slightly better than those taking a placebo in the short term and do no better in the long term. The effectiveness of a drug is then judged by balancing the gains against placebo, if there are any, with the adverse effects associated with the drug, as well as other considerations. Stimulants do have effects, of course. They are not inert. Low-dose stimulants modify behaviour in animals and humans alike, improving attention and focus on mundane tasks. ¹ Animal studies also show that this effect is accompanied by a reduction in spontaneous exploratory behaviour, interest in the environment and social interaction. ^2,3 Moreover, any initial effects may decline due to tolerance, which, although little investigated in the case of therapeutic stimulant use, is known to occur in response to most psychoactive substances.