The current findings should be interpreted in the context of 6 potential methodological limitations. First, we examined only twins from male-male pairs born in Virginia. (Endorsement rates of several CD criteria in female-female pairs were too low for meaningful analysis.) Our results may not extrapolate to females or other ethnic groups. Second, our analyses used CD criteria from DSM-III-R17 not DSM-IV.1 Two criteria were omitted because of rarity, and 2 others were collapsed. However, 9 of the 10 DSM-III-R items assessed were similar to DSM-IV CD criteria, with all criterion subsets represented: aggression to people/animals (3 items), property destruction (2 items), deceitfulness/theft (2 items), and serious rule violations (2 items). Third, CD criteria in the current study were assessed by self-report questionnaire, not structured interview. However, for socially undesirable traits like CD behaviors, research suggests that more accurate responses are obtained by more anonymous means of as sessment.35 Furthermore, several prior studies support the validity of self-report assessment of CD.36-38 Fourth, CD symptoms were reported retrospectively. We can not, therefore, rule out a substantial effect of memory bias. It is,
