Long-term usefulness of thioridazine for institutionalized mentally retarded patients.

Thioridazine (Mellaril) medication was discontinued for 4 to 5 weeks for 106 institutionalized mentally retarded patients after an extended period of previous drug treatment. Time-sampling of behavior while patients were receiving medication and while receiving placebo showed a significant increase in self-stimulation and active negative behavior and decreased work and life skills while receiving placebo. Although most patients' behavior was better while on active medication, some showed significant improvement when medication was temporarily discontinued. Favorable long-term progress among those who had medication restored was greater for patients whose behavior had worsened to the greatest degree during the placebo trial.