|Vol. 4, No. 1, 1998 Page 6|
Last year, Wendy Slutske and colleagues reported that genes strongly influence whether or not children develop conduct disorder (see related article, Crime Times, 1997, Vol. 3, No. 3, Page 1). In a new study, Peter McGuffin and Anita Thapar report similar findings.
The researchers studied antisocial behaviors in adolescent twins, using information from questionnaires sent to 43 monozygotic ("identical") and 38 dizygotic ("fraternal") same-sex twins. Their data suggest, McGuffin and Thapar say, "that common bad behaviors of the sort admitted to by the majority of adolescents have a substantially heritable component. Additive genetic effects account for most of the variation, with no evidence of a contribution from shared environment."
The researchers say these results are quite different from those of an earlier study (also by McGuffin and Thapar) of younger children, between the ages of 8 and 16. In the younger group, they say, bad behavior appeared to be largely determined by environmental factors. "However," they say, "the finding of higher heritability in adolescents is in keeping with the tendency for other behavioral traits to show increasing genetic effects over time." For instance, they note, the effects of genes on cognitive ability increase considerably with age.
"Genetic basis of bad behaviour in adolescents," Peter McGuffin and Anita Thapar, The Lancet, Vol. 350, August 9, 1997, pp. 411- 412. Address: Peter McGuffin, Division of Psychological Medicine, University of Wales College of Medicine, Heath Park, Cardiff CF4 4XN, UK.