GENETIC AND SHARED ENVIRONMENTAL-INFLUENCES ON ADOLESCENT BMI - INTERACTIONS WITH RACE AND SEX

The present study uses a behavioral genetic design to investigate the genetic and environmental influences on variation in adolescent body m ass index (BMI) and to determine whether the relative influences of ge netic and environmental factors on variation in BMI are similar across racial groups and sexes. Data for the present study come from the Nat ional Longitudinal Study on Adolescent Health (Add Health), a large, n ationally representative study of adolescent health and health-related behaviors. The Add Health sample contains a subset of sibling pairs t hat differs in levels of genetic relatedness, making it well suited fo r behavioral genetics analyses. The present study examines whether gen etic and environmental influences on adolescent BMI are the same for m ales and females and for Black and White adolescents. Results indicate that genetic factors contribute substantially to individual differenc es in adolescent BMI, explaining between 45 and 85% of the variance in BMI. Furthermore, based on an analysis of opposite-sex sibling pairs, the genes that influence variation in adolescent BMI are similar for males and females. However, the relative importance of genetic and env ironmental influences on variation in BMI differs for males and female s and for Blacks and Whites. Although parameter estimates could be con strained to be equal for Black and White males, they could not be cons trained to be equal for Black and White females. Moreover, the best-fi tting model for Black females was an ADE model, for White females it w as an ACE model, and for males it was an AE model. Thus, shared enviro nmental influences are significant for White female adolescents, but n ot for Black females or males. Likewise, nonadditive genetic influence s are indicated for Black females, but not for White females or males. Implications of these results are discussed.