Declared Rationale for Cannabis Use Before and After Legalization for Nonmedical Use: A Longitudinal Study of Community Adults in Ontario

Objectives: To examine the proportion of individuals using cannabis for medical purposes who reported nonmedical use of cannabis after it became legal to do so.Materials and Methods: We acquired data from the Population Assessment for Tomorrow's Health, the Cannabis Legalization Surveillance Study on a subpopulation of participants residing in Hamilton, Ontario, Canada, who reported using cannabis for medical purposes. Specifically, we acquired data 6 months before, and again 6 months after, legalization of cannabis for nonmedical purposes. We constructed a logistic regression model to explore the association between potential explanatory factors and endorsing exclusively nonmedical use after legalization and reported associations as odds ratios and 95% confidence intervals.Results: Our sample included 254 respondents (mean age 33 +/- 13; 61% female), of which 208 (82%) reported both medical and nonmedical use of cannabis (dual motives) before legalization for nonmedical purposes, and 46 (18%) reported cannabis use exclusively for medical purposes. Twenty-five percent (n=63) indicated they had medical authorization to use medical cannabis, of which 37 (59%) also endorsed nonmedical use. After legalization of nonmedical cannabis, similar to 1 in 4 previously exclusive cannabis users for medical purposes declared dual use (medical and nonmedical), and similar to 1 in 4 previously dual users declared exclusively nonmedical use of cannabis. No individual with medical authorization reported a change to exclusively nonmedical use after legalization. Our adjusted regression analysis found that younger age, male sex, and lacking authorization for cannabis use were associated with declaring exclusively nonmedical use of cannabis after legalization. Anxiety, depression, impaired sleep, pain, and headaches were among the most common complaints for which respondents used cannabis therapeutically. Most respondents reported using cannabis as a substitute for prescription medication at least some of the time, and approximately half reported using cannabis as a substitute for alcohol at least some of the time.Conclusions: In a community sample of Canadian adults reporting use of cannabis for medical purposes, legalization of nonmedical cannabis was associated with a substantial proportion changing to either dual use (using cannabis for both medical and nonmedical purposes) or exclusively nonmedical use. Younger men without medical authorization for cannabis use were more likely to declare exclusively nonmedical use after legalization.