Clinical and cognitive effects of methylphenidate on children with attention deficit disorder as a function of aggression/oppositionality and age.

Children diagnosed with attention deficit disorder (ADD; n = 44), ADD plus aggression/oppositionality (ADD/O; n = 34), and as not meeting ADD criteria (NC; n = 29) received methylphenidate and placebo for 21 consecutive days each. Parents and teachers rated all groups improved under medication, but teachers reported less improvement for NC than for ADD/O children. Methylphenidate and chronological age had generally similar effects in a Sternberg task: greater accuracy and speed (especially for nontargets at low memory loads), larger P3b waves of event-related potentials, more pronounced slowing of P3b latency by memory load, and a greater trend of earlier peaks for targets than for nontargets. Both methylphenidate and maturation promoted more efficient strategies involving differentiated evaluation of targets and nontargets. These results were comparable among ADD groups.