Motor/vocal tics and compulsive behaviors on stimulant drugs: is there a common vulnerability?

The occurrence of abnormal movements or perserverative/compulsive behaviors was noted in 34 (76%) of a group of 45 hyperactive boys during a double-blind crossover treatment trial of methylphenidate and dextroamphetamine given in a wide range of doses. These adverse effects were often subtle and transient, and they usually occurred only on one drug. There was only one case where treatment was discontinued due to the severity of the tic the subject developed during his initial treatment phase. Dextroamphetamine tended to produce more compulsive behaviors, which were also more likely to resemble clinical obsessive-compulsive disorder (OCD), than did methylphenidate. Abnormal movements and compulsive behaviors tended to co-occur on methylphenidate only; no general "Tourette-OCD diathesis" was found for this population.