OBJECTIVE:

To determine to what extent the clinical response to methylphenidate (MPH) is affected by psychiatric comorbidities in children diagnosed with attention-deficit hyperactivity disorder (ADHD).

METHODS:

Children (n = 267) aged 6 to 12 years diagnosed with ADHD participated in a double-blind, placebo-controlled, 2-week medication trial of MPH. Children were assessed using parent and teacher ratings and laboratory measures. Clinical response to MPH was determined by integrating all obtained measures.

RESULTS:

Meeting criteria for conduct disorder (CD) was 27.7% of children, 40.8% for oppositional defiant (ODD), 47.2% for anxiety, and 7.9% for depressive disorders. The presence of CD or ODD was associated with good response to MPH. In contrast, children diagnosed with only comorbid anxiety were more likely to receive poor response rating independent of age, sex, or socioeconomic status. Low family income was found to be predictive of good response to MPH.

CONCLUSIONS:

The response to MPH in children with ADHD may be dependent on the type of comorbid disorder present.

CLINICAL TRIAL REGISTRATION NUMBER:

NCT00483106.