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Jerald G. Bachman, Lloyd D. Johnston, Patrick M. O'Malley, Explaining the Recent Decline in Cocaine Use among Young Adults: Further Evidence That Perceived Risks and Disapproval Lead to Reduced Drug Use, Journal of Health and Social Behavior, Vol. 31, No. 2 (Jun., 1990), pp. 173-184
Bachman et al. (Fri,) studied this question.