Sex differences in attentional performance and their modulation by methylphenidate in children with attention-deficit/hyperactivity disorder

Abstract

Background: Still little is known about neuropsychological differences between boys and girls with attention-deficit/hyperactivity disorder (ADHD) and whether there are sex-specific differences in the modulation of attentional performance by methylphenidate (MPH).

Method: In this study, 27 males and 27 females between 8-12 years old and with ADHD were investigated in a double-blind, placebo-controlled trial on five computerized attention tests (0.25 vs. 0.5 mg/kg MPH as a single dose, versus placebo).

Results: Boys and girls with ADHD did not differ with respect to age, intelligence quotient (IQ), symptom severity, co-morbidity patterns, and ADHD subtype. However, ADHD boys were more impulsive on a sustained attention task, whereas girls with ADHD had more deficits on tasks measuring selective attention. Attentional performance increased differentially as a function of MPH dose, with some tasks showing linear improvement with higher dosage whereas more complex tasks in particular showed inverse U-shaped patterns of MPH effects. However, these effects were comparable between girls and boys.

Conclusions: Our data suggest that there are some gender differences in attentional performance in subjects with ADHD in a clinical sample, even if symptom severity and co-morbidity are controlled; however, modulation of attention by MPH does not seem to differ between sexes.