Differential Response to Methylphenidate in Inattentive and Combined Subtype ADHD

Abstract

Objective: To examine response to methylphenidate (MPH) assessed by direct observation of ecologically valid behaviors in boys with ADHD with high hyperactivity-impulsivity (HI) and those with predominantly inattentive symptoms (ADHD/I).

Method: Sixty-three boys ages 7 to 13 participated in an ADHD Summer Treatment Program and received a double-blind placebo-controlled assessment of .3 mg/kg of MPH on problem behaviors and individualized behavior goals. Medication effect sizes were calculated for each child for each behavior.

Results: Children with ADHD/HI ( n = 21) displayed larger MPH effect sizes for interrupting, verbal abuse, and compliance, and marginally greater response for teasing and counselor-directed goals. Children with ADHD/I ( n = 21) displayed small medication effect sizes ( ds < .20) for many behaviors often identified as primary deficits in this group (e.g., attention to activities, peer interaction, class work completion, and accuracy).

Conclusion: Systematic medication assessment for ADHD/I that quantifies response in ecologically valid areas of functional impairment is essential.

Keywords: ADHD subtypes; medication treatment; methylphenidate.