| This dissertation addressed three primary aims. First, I conducted a systematic literature review to assess the evidence for birth cohort effects in alcohol consumption, disorder, and mortality. Thirty-two articles were included. Evidence suggests that younger birth cohorts, especially those born after World War II, are more likely than older cohorts to engage in heavy episodic drinking and develop alcohol disorders. This cohort effect appears to exist in North America and Eastern Europe, but not in Australia and Western Europe. Women in younger-born cohorts are at especially high risk for heavy episodic drinking and alcohol disorders.;Second, I investigated whether adolescents in birth cohorts and/or time periods with high disapproval of alcohol and cigarette use were at decreased risk for alcohol and cigarette use, controlling for personal attitudes towards use and age. Data were drawn from the Monitoring the Future study, a nationally-representative annual survey of 8th, 10th, and 12th grade students conducted from 1976 through 2007. Social norms were measured by a period- and cohort-specific score incorporating the percentage of the population disapproval of alcohol and cigarette use. I employed cross-classified random effects models with individuals clustered in time periods of observation and birth cohorts, and modeled period- and cohort-specific score on social norms as predictors in a multi-level modeling framework. Individuals who matured in disapproving cohorts were less likely to use alcohol compared to individuals who matured in less disapproving cohorts; each 5% increase in the disapproval of the birth cohort was associated with a 25% decrease in the odds of past-year alcohol use (OR=0.75, 99% C.I. 0.72--0.78). The effects of disapproval were notably stronger among White than Black adolescents. In contrast, period-specific disapproval predicted cigarette use; each five percentage point increase in period-specific disapproval was associated with a 20% decrease odds (OR=0.81 99% C.I. 0.79--0.82).;Third, I investigated whether adolescents in birth cohorts and/or living in time periods with high disapproval of marijuana use were at decreased risk for marijuana use, controlling for individuals' perceptions of social norms, attitudes toward marijuana, as well as socio-demographics. Individuals in disapproving cohorts were less likely to use marijuana compared to individuals in less disapproving cohorts, controlling for individual-level attitudes, perceived norms and availability, socio-demographic factors including age as well as population-level time period. Each five percentage point increase in cohort-specific disapproval was associated with a 12% decrease in the odds of past-year marijuana use (OR=0.88, 99% C.I. 0.87--0.89, p=0.004). Compared to cohorts in which 87--90.9% of adolescents disapproved of marijuana use, odds of marijuana use were 3.53 times higher in cohorts where 42--46.9% of adolescents disapproved (99% C.I. 2.75, 4.53).;Taken together, this dissertation documents the importance of considering time-varying population-level risk factors in the study of adolescent substance use. Further, this research suggests that social norms and attitudes regarding marijuana and alcohol use cluster in birth cohorts, and this clustering has a direct effect on risk for marijuana and alcohol use that remains even after controlling for individual perceptions of attitudes and norms. Finally, this dissertation research indicates that underlying processes for the impact of changing social norms on alcohol, marijuana, and cigarette use in adolescence differ, suggesting that theories regarding the effects of macro-level processes on drug use need to be developed in a substance specific manner. This dissertation work further indicates that public health invention and prevention efforts aimed at changing societal norms towards alcohol and drug use may be effective in shifting the population prevalence of adolescent substance use. |
