Long-term follow-up of children with mental retardation/borderline intellectual functioning and ADHD.

Fifty-two children (ages 7 to 14 years) with moderate retardation to borderline intellectual functioning were recontacted 12 to 65 months following participation in a double-blind, placebo-controlled trial of methylphenidate (MPH). Sixty-nine percent of subjects continued to be prescribed medication for behavior control at follow-up. While 72% of the sample evidenced improvement, over two-thirds continued to be rated at or above the 98th percentile on the Hyperactivity Index of the Parent Conners. In fact, 22% of subjects had received inpatient psychiatric treatment between the time of the initial MPH trial and follow-up. Finally, subjects with high initial ratings on the Parent Conners Conduct Problems scale were more likely to be suspended from school or receive inpatient psychiatric treatment than subjects with low initial ratings. The results suggested that children with ADHD and mental retardation of borderline intellectual functioning continued to exhibit significant symptoms associated with attention deficit hyperactivity disorder (ADHD) at follow-up and that early conduct problems were predictive of continuing behavioral difficulties.