Background. To examine the familial associations of overt and covert antisocial behavior within the diagnosis of conduct disorder (CD) in families ascertained by referred children with attention-deficit hyperactivity disorder (ADHD), and to test if these familial associations differed between male and female probands.

Method. Subjects were clinically-referred male and female ADHD children (n=273) and their first-degree biological relatives (n=807). Scores for overt and covert conduct problems were calculated by summing the DSM-III-R conduct disorder symptoms, as derived from structured diagnostic interviews. Familial aggregation analyses were conducted with multivariate regression modeling methodology.

Results. Proband overt scores significantly predicted the overt scores of their relatives, and proband covert scores significantly predicted the covert scores of their relatives. There was no evidence of covert symptom scores predicting overt scores or vice versa. There was some evidence that the aggregation of covert symptoms was stronger in the families of female probands.

Conclusions. These results provide preliminary evidence that overt and covert conduct disorder symptoms are independently transmitted through families and may represent distinct familial syndromes.