The datasets used in this study are large and have complementary designs, but there are potential limitations. First, both studies relied on in-person measurements of self-reported alcohol use, rather than anonymous reports. This is of concern because when comparing alcohol use from in-person surveys to anonymous surveys, the in-person surveys show under-reporting of alcohol use (Polich 1982; Del Boca and Darkes 2003). In addition, although outcomes were measured at the end of the study period, alcohol use patterns were measured once. This likely resulted in higher variance than if repeated measures of use were available.
