A prevailing epidemiological theory about occurrence of drug use among secondary school students is that use follows trends in perceived risk of drug-related harms. If so, one might expect occurrence and clustering of drug use to occur more often in schools with concurrent or previously low levels of drug risk perceptions. This thesis aims to estimate the degree to which cannabis use might be clustering among secondary school students in the United States and to investigate a hypothesis about the prediction from the senior class’s cannabis risk perceptions in one school year to the occurrence of newly incident cannabis use in the next year’s senior class. Each year from 1976-2013, roughly 16,000 12th graders in ~133 schools completed questionnaires with standardized survey items for the Monitoring the Future study. The statistical approach harnessed Alternating Logistic Regressions to derive pairwise odds ratio estimates (PWOR), with PWOR > 1 providing evidence of clustering and a possible ‘contagion’ process, as well as regression slopes to estimate effect of prior year risk perception on next year risk of initiating cannabis use. The PWOR estimate is consistent with modest clustering of cannabis use suggestive of within-school social sharing of cannabis or ‘contagion’ (PWOR = 1.11; 95% CI = 1.06, 1.16). Statistically robust regression slope estimates suggest a lower risk of becoming a newly incident user for each risk perception unit (OR = 0.10; 95% CI = 0.03, 0.33). The most important discovery might be that school-level risk perceptions of 12th graders in one year may account for occurrence of newly incident cannabis use among seniors the next year. A causal link can be confirmed by experimental manipulation of perceived risk via public health interventions.
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