There are a number of important limitations to the present study. The 1970’s were a turbulent era, and MLDA laws were not the only social processes that might have affected lifetime patterns of alcohol and other substance use for cohorts coming of age in this period. However, we have greatly narrowed the range of possible explanations by comparing cohorts coming of age in the 1970’s (when drinking ages were being lowered) and in the 1980’s (when drinking ages were being raised again), and by comparing subjects close in age who were coming of age just before and after a change in state law. If the apparent MLDA effects are not attributable to changing drinking-age laws themselves, then they are due to an environmental factor closely tied to the timing of these changing laws.
