School context and genetic influences on aggression in adolescence

Genetic and environmental contributions to variation in aggression were exa mined using adolescents' self-reports of aggressive behavior The National L ongitudinal Study of Adolescent Health provided a sample of 1,515 pairs of adolescents in five genetically informative groups (i.e., monozygotic twins , dizygotic twins, full siblings, half siblings, and unrelated siblings rea red together). The analysis a DeFries-Fulker regression within a hierarchic al linear model, yielded findings on individual-level heritability (h(2)), shared environmental effects (c(2)), school-level effects, and school-level moderation of h(2) and c(2). The estimate of h(2) for aggression in the fu ll sample was .32, and c(2) was .05. In the moderating effect, h(2) increas ed and c(2) decreased with greater school-level family warmth. Two effects on school means were Sound: Those schools with greater ethnic-racial hetero geneity had higher mean levels elf aggression, and schools where students p erceived greater family warmth had lower mean levels of aggression.