Etiology of the impulsivity aggression relationship: Genes or environment?

Genetic and environmental influences on the phenotypic relationship between the Barratt Impulsiveness Scale and the aggression scales from the Buss-Du rkee Hostility Inventory in adult males were examined. This study used 182 pairs of male MZ twins and 118 pairs of male DZ twins from the Vietnam Era Twin Registry. Phenotypic relationships between the measure of impulsivity and subscales of the measure of aggression (direct assault, verbal assault, indirect assault, and irritability) ranged from 0.22 to 0.51. Genetic and environmental mediation of the phenotypic relationship between impulsivity and aggression were approximately the same for all four models. Multivariat e model-fitting analysis indicated that irritability and impulsivity had a larger phenotypic relationship, as well as a greater portion of shared gene s and environment than the other three subscales of aggression. This sugges ts, for example, that there are more overlapping genetic and environmental influences accounting for the relationship between irritability and impulsi vity than between direct assault and impulsivity. The effects of such findi ngs on our understanding of impulsive aggression are discussed. (C) 1999 El sevier Science Ireland Ltd. All rights reserved.