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.