Jessica L. Bar1, Irwin D. Waldman1, David A. Hay2, & Florence Levy3
Conduct disorder (CD) is a serious childhood disorder, characterized by extreme and persistent antisocial behavior. Relatively few behavior genetic studies on childhood CD per se have been conducted. Behavior genetic studies on childhood antisocial behavior and delinquency have yielded mixed results, with many finding substantial genetic influences and some finding appreciable shared environmental influences. One mechanism by which genetic influences may operate is by predisposing a child to be more susceptible to environmental influences. Sociological studies have found correlations between antisocial behavior and various demographic factors (e.g., urban vs. rural residence, low SES, high crime), but the causal status of these factors is ambiguous. Behavior genetic designs can help elucidate the causal mechanisms by which such variables operate. In this study we examined demographic characteristics of neighborhoods and communities to examine the extent to which the genetic and environmental influences on CD vary across environmental contexts. The participants were 2183 4-14 year old male and female same- and opposite-sex twin pairs and their siblings (962 MZ pairs, 963 DZ pairs, and 258 sibling pairs) recruited from the Australian NHMRC Twin Registry, a nationwide, population-based, volunteer registry. Information on zygosity was based on mothers' reports of their twins' physical similarity. The mothers of twins filled out a questionnaire assessment of 6 DSM-III-R CD symptoms. We used multiple regression analyses of twin and sibling data to estimate genetic and environmental influences on CD symptoms and their moderation by environmental context variables. The implications of our results for the causal role of demographic factors in childhood antisocial behavior will be discussed.
Address: Department of Psychology, Emory University, Atlanta, GA, 30322, phone - (404) 727-2741, fax - (404) 727-1284, e-mail - jbar@emory.edu
1Department of Psychology, Emory University, Atlanta, GA 30322. 2Department of Psychology, Curtin University, Perth, Western Australia, Australia. 3Department of Child and Adolescent Psychiatry, The Prince of Wales Children's Hospital, High Street, Randwick, NSW 2031, Australia.