Methylphenidate and thioridazine in the treatment of intellectually subaverage children: effects on cognitive-motor performance.

Twenty-seven children (or smaller subgroups depending upon task difficulty and subject ability) with subaverage IQs took part in a double-blind, placebo-controlled, cross-over study of methylphenidate (0.4 mg/kg/day) and thioridazine (1.75 mg/kg/day). The children were tested for IQ performance, breadth of attention, and performance on a series of electronically controlled cognitive-motor tests. Methylphenidate improved accuracy on a memory task, reduced omission errors on an attentional task, and reduced seat movements on two tasks. Thioridazine failed to have any deleterious effects on IQ performance when subjects received reinforcers for correct answers. Thioridazine at the given dose did not adversely affect performance on any of the cognitive-motor performance tests. Methylphenidate appears likely to enhance sustained attention and motivation in appropriately selected children with mild developmental delays, whereas thioridazine at this modest dose does not appear to impair performance on most psychomotor tests.