The role of family background and cognitive ability on smoking and body mass index during adolescence and in young adulthood.

The purposes of this research was to investigate (a) to what extent family background and adolescent cognitive ability affected smoking and body mass index (BMI) during adolescence; and (b) whether post high-school socioeconomic position (SEP) was associated with smoking and BMI in early adulthood. Three analyses were conducted in a nationally representative sample of US adolescents: (a) a longitudinal analysis of repeatedly measured smoking for the role of adolescent cognitive ability and family background on smoking during adolescence; (b) a longitudinal analysis of repeated measured BMI for the effects of the same set of variables on BMI during adolescence; and (c) a cross-sectional analysis for the association of achieved socioeconomic position with smoking and BMI in young adulthood. Results showed that family socioeconomic background was not strongly associated with smoking over adolescent years, but the presence of a smoker in the household and having easy access to cigarettes at home were strong predictors. Although adolescent cognitive ability was inversely related to the risk of heavy smoking during adolescence, the association was explained by adolescent academic achievement. Poor family SEP was associated with increased BMI in girls but not among boys, independently of parental obesity. An inverse relation was found between cognitive ability and BMI over time only among girls. However, the association was confounded by family SEP, in particular by maternal education. Strong socioeconomic gradients in smoking and BMI emerged when socioeconomic position was measured by the adolescents achieved SEP in early adulthood. The observed socioeconomic gradients were not explained by potentially important family background and individual characteristics during adolescence. In sum, there is no strong effect of family socioeconomic circumstances on adolescent smoking and BMI over time, yet the socioeconomic gradients emerge by early adulthood, suggesting that behavioral crystallization by socioeconomic position occurs between adolescence and young adulthood. Even though adolescent cognitive ability is somewhat related to smoking and BMI during adolescence, the association is inconsistent across sexes and outcomes, providing little support for the hypothesis that pre-adult cognitive ability affects health in later life via behaviors.Ph.D.Health and Environmental SciencesPublic healthUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125782/2/3208576.pd