Methylphenidate treatment in children with borderline IQ and mental retardation: Analysis of three aggregated studies

Objective: To determine response of low-IQ children with attention deficit hyperactivity disorder (ADHD) symptoms to methylphenidate (MPH). Methods: An aggregated analysis was conducted in 90 children with low IQ who received the same dose regimen of MPH in three independent, placebo-controlled studies. Active drug and placebo were given from 2 to 4 weeks each. Outcome measures included teacher and parent ratings on standardized behavior scales (mean n = 84), performance on computer-controlled cognitive-motor tests (n = 62), and measures of cardiovascular response (n = 85). Results: Both teachers and parents rated the children consistently as being improved on subscales assessing attention, overactivity, and conduct problems. Some 44% of the subjects showed at least a 30% reduction compared with placebo on teacher ratings. MPH improved accuracy on several cognitive tests, response speed was increased on some, and seat activity declined for one of three tests; heart rate was mildly increased (3.9 beats/minute) with MPH. Analyses of IQ and mental age as moderator variables suggested that lower functional level (especially lower IQ) may be associated with a less favorable response to MPH. Conclusions: Children with low IQ and ADHD clearly respond to MPH, but their rate of beneficial response appears to be well under that of normal-IQ children and more varied. Different attentional mechanisms may moderate response to psychostimulants.