A negative interaction of exactly this sort was found fairly consistently across countries. All 17 interactions for alcohol use were <1.0 (14 of them significant at the 0.05 level). Seven of nine interactions were <1.0 in predicting tobacco use (five of them significantly so). The comparable counts were 13 of 15 interactions (five significant) in predicting use of cannabis, and six of 11 (two significant) in predicting cocaine use. It is noteworthy that the interactions are less consistent for illegal drugs, although the pattern is in the same direction as for the legal drugs.
