In the present study, we use these MLDA policy experiments to investigate the relationship between adolescent drinking exposures and the past-year prevalence of DSMIV alcohol and substance use disorders in cohorts evaluated from age 20 to age 54. The state-by-state variation in the timing of changes in the MLDA allows us to use state and year fixed effects to purge our estimates of potentially confounding influences that are relatively constant within a state, or common to each birth cohort across states (e.g., Angrist and Pischke 2009, Cook and Campbell 1979), and the pooling of two large, nationally representative cross-sectional surveys conducted in 1991–1992 and 2001–2002 makes it possible to distinguish the effects of birth cohort from the effects of age at assessment. Some of our regression models also control for parental alcoholism, state-specific linear time trends, and for per capita alcohol consumption and state beer taxes in the year that the respondent turned 18. However, a possible concern in a study design of this kind is that some other, unobserved social process might better explain an apparent link between MLDA
