Randomized controlled trials and meta-analyses indicate that stimulant medication improves symptoms in approximately 80 percent of children with ADHD without ASD. In randomized crossover trials, methylphenidate also improved symptoms of hyperactivity and inattention in children with ASD. However, the response rate to methylphenidate is lower in children with ASD than it is in children with ADHD without ASD.
In the largest crossover trial, approximately 50 percent of children with ASD responded to methylphenidate; the effect size ranged from 0.29 to 0.54, depending upon dose, with greater improvement at higher doses (0.25 to 0.5 mg/kg versus 0.125 mg/kg per dose). Methylphenidate also may have beneficial effects on social communication and self-regulation.
Studies of amphetamines (dextroamphetamine, amphetamine-dextroamphetamine) in the treatment of attentional symptoms in children with ASD are lacking. It is not clear that the results from trials of methylphenidate can be generalized to amphetamines. However, amphetamines frequently are used in clinical practice.
The side effects of stimulant medications in children with ASD are similar to those in other patients. However, they occur with greater frequency. In the trial of methylphenidate described above, 18 percent of subjects withdrew because of adverse effects. In comparison, in a large randomized trial of stimulants for attention deficit disorder in children without ASD, the dropout rate was only 3.5 percent. Adverse effects of stimulant medications include, but are not limited to, sleep disturbance, decreased appetite, irritability, tics, sadness, dullness, and social withdrawal.