Why have drug treatments been so disappointing?

The title of this contribution involves two consecutive questions: have the effects of medication in autism indeed been disappointing? And if so, why? The answer to the first question depends on whether one focuses on the core social and communicative deficits of autism, or on various complicating behaviour problems. Attempts over the past decades to develop drugs that specifically improve social and communicative functioning have failed. Among the most ambitious attempts were medical interventions in the endogenous opioid system that were motivated from animal models on the involvement of this system in various aspects of social behaviour. By contrast, medications such as the newer antipsychotics, psychostimulants, presynaptic noradrenergic blocking agents (clonidine and guanfacine) and selective serotonin reuptake inhibitors were shown to reduce impairing complicating symptoms of affective instability, irritability, hyperactivity and inattentiveness, aggression, self-injury and stereotypies. The explanation for the medication-refractory status of social and communicative deficits should be sought in at least two related factors: (1) the as yet unidentified neurochemical basis of autism, and (2) the obvious lack of involvement of the main neurotransmitter systems (dopamine, noradrenaline and serotonin) in the pathophysiology of social and communicative behaviour.