The Massachusetts General Hospital studies of gender influences on attention-deficit/hyperactivity disorder in youth and relatives

The substantial discrepancy in the male-to-female ratio between clinic-referred (10 to 1) and community samples (three to one) of children with attention-deficit/hyperactivity disorder (ADHD) suggests that gender differences may be operant in the phenotypic expression of ADHD. In this study, the authors systematically examined the impact of gender on the clinical features of ADHD. The authors conducted a study of 140 boys with ADHD, 140 girls with ADHD, 120 non-ADHD boy comparisons, and 122 non-ADHD girl comparisons. These groups had 454 and 368 first-degree biological relatives, and 417 and 369 first-degree biological relatives, respectively. All subjects were assessed systematically with structured diagnostic interviews and neuropsychological batteries for subtypes of ADHD, emotional, school, intellectual, interpersonal, and family functioning. Girls with ADHD were more likely than boys to have the predominantly inattentive type of ADHD, less likely to have learning disability, and less likely to manifest problems in school or in their spare time. In addition, girls with ADHD were at a reduced risk for comorbid major depression, conduct disorder, and oppositional defiant disorder. Also, a statistically significant gender by ADHD interaction was identified for comorbid substance use disorders. The co-occurrence of ADHD and comorbid psychopathology in families was the same for families ascertained through boy and girl probands. The lower likelihood for girls to manifest psychiatric, cognitive, and functional impairment than boys could result in gender-based referral bias unfavorable to girls with ADHD. The results also suggest that boys and girls do not differ in the familial risk factors that mediate comorbid psychopathology and the familial aggregation of comorbid disorders in ADHD families.