Chunk #58 — II. G × E Interaction in Aggressive Behavior — A. Potential moderators of genetic influence found in adoption and twin studies — 1. Family adversity and social disadvantage
G × E interaction for aggressive behavior has been found in several of the early adoption studies, using a mean levels approach. What these early adoption study findings generally showed was that early adverse environments had a greater negative impact on genetically “higher risk” children. Adopted children with criminal biological parents reared by a family where there was adversity showed higher rates of antisocial and aggressive behavior than adopted children with antisocial biological parents not raised in a home with adversity, and than adopted children raised in adversity who are not at higher genetic risk. For example, the interaction of inherited and postnatal factors was examined in about 800 Swedish men adopted at an early age. When both inherited factors and environmental risk factors were present, 40% were found to be criminal; if only genetic factors were present, 12.1% were criminal; if only environmental factors were present, 6.7% were criminal; and with neither inherited nor environmental factors being present, 2.7% were criminal (Cloninger et al., 1982). The fact that 12.1% plus 6.7% is less than 40% would thus be an
