A family study of psychiatric comorbidity in girls and boys with attention-deficit/hyperactivity disorder

Background: Because attention-deficit/hyperactivity disorder (ADHD) is rela tively infrequent among girls, little is known about the nature and causes of psychiatric comorbidity in girls and the reason for gender differences i n the prevalence of these comorbidities. Methods: Using blinded, structured psychiatric interviews, we studied two g roups of boys: 140 ADHD probands and 120 non-ADHD comparisons. These groups had 454 and 368 first-degree biological relatives, respectively. We also s tudied two groups of girls: 140 ADHD probands and 122 non-ADHD comparisons. These groups had 417 and 369 first-degree biological relatives, respective ly. Results: The co-occurrence of ADHD and comorbid psychopathology in families was the same for families ascertained through boy and girl probands. Conclusions: Our results suggest that boys and girls do not differ in the f amiliar risk factors that mediate comorbid psychopathology and the familial aggregation of comorbid disorders in ADHD families. Although this is consi stent with prior work suggesting more similarities than differenceS in the nature of psychiatric comorbidity in ADHD boys and girls, we cannot make st rong conclusions, owing to the possibility of cohort effects. (C) 2001 Soci ety of Biological Psychiatry.