|Vol. 3, No. 3, 1997 Page 1|
Data from a new study of 2,682 adult twin pairs reveal "a substantial genetic influence on risk for conduct disorder (CD)," according to researchers in the United States and Australia. Symptoms of CD, usually identified in childhood, include chronic steal l l l l l ling, lying, bullying, arson, property destruction, weapons use, physical cruelty to animals or people, fighting, aggression, truancy, and/or running away from home.
Wendy Slutske and colleagues say their data revealed that "the best-fitting model [for risk of developing CD] yielded a point estimate of heritability of 71%," but did not reveal any clear effect of shared family environment. However, the researchers say that "a modest effect of the shared environment on the risk for CD could not be excluded."
Boys are identified as having conduct disorder far more often than girls, but the researchers found that "the magnitude of genetic and environmental influences for CD liability did not vary significantly for boys and girls." They also found evidence that conduct disorder is not a discrete disorder, but rather "an extreme of the normal variation in conduct-disordered behavior found in the general population."
Study data revealed that twins who shared childhood playmates were more likely than other twins to be concordant for CD-that is, to both be identified as having the disorder. The researchers note, however, that this may be a result of genetic factors as well, "because there is evidence to suggest that peer choice is itself a genetically driven behavior."
Likewise, they say, this study suggests that the association of CD in children with disturbed behavior in their parents is likely to stem more from genetic than from environmental factors. "If this is true," Slutske et al. say, "then modification of paren n n n n nt characteristics may not have the anticipated effect of reducing antisocial behaviors in their children." The researchers stress that the relative unimportance of environmental factors in conduct disorder should not discourage professionals seeking treatments for conduct-disordered children. "The genetic etiology of a disorder does not imply immutability," th h h h h hey note, "and there are many examples of genetically influenced traits that have been modified through environmental interventions."
"Modeling genetic and environmental influences in the etiology of conduct disorder: a study of 2,682 adult twin pairs," Wendy Slutske, Andrew Heath, Stephen Dinwiddie, Pamela Madden, Kathleen Bucholz, Michael Dunne, Dixie Statham, and Nicholas Martin, > > > > >Journal of Abnormal Psychology, Vol. 106, No. 2, 1997, pp. 266-279. Address: Wendy Slutske, Dept. of Psychiatry, Washington University School of Medicine, Box 8134, 4940 Children's Place, St. Louis, MO 63110-1093.