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The Impact of City Bans on Medical Marijuana Dispensaries on Marijuana Use Among High School Students in Los Angeles County, California


As marijuana policy continues to rapidly evolve in California and LA County, many regulatory approaches have been undertaken with very little evidence of their effectiveness. After storefront medical marijuana dispensaries became legal in California in 2005, some cities chose to allow them while others chose to ban them. To date, however, no empirical research has documented whether banning dispensaries or allowing and regulating them results in less harm to communities. Even less is known about which approach is more effective at achieving a policy goal that unites all sides of the debate on marijuana legalization: preventing adolescent marijuana use.

This dissertation examined the impact of city policies restricting or banning medical marijuana dispensaries on the marijuana use behaviors of public high school students in Los Angeles County, California. My first research question was whether city laws that ban or enact more restrictions on dispensaries have a preventative impact on marijuana use among high school students. My other research questions concerned what other factors might be important determinants of whether stricter dispensary regulations or total bans on dispensaries were effective in preventing high school students’ cannabis use. I theorized that the effectiveness of dispensary bans would be at least partially dependent on effective enforcement and that MMD bans would be positively correlated with greater perceptions of the risk of marijuana use among adolescents. I therefore examined the degree to which the relationship between dispensary bans and student marijuana use was mediated by the actual number of dispensaries in the city, how dispensary bans impacted students’ perceptions of the risk of marijuana use, how close dispensaries were located to participants’ schools, and how many dispensaries were located in the close vicinity of the school.

Neither dispensary bans nor the number of dispensaries in a city (normalized by population to a rate of dispensaries per 10,000 city residents) were associated with student marijuana use in cross sectional analyses comparing the prevalence of student marijuana use across 57 cities in LA County. While lower risk perceptions were related to higher use, city dispensary bans were not directly related to students perceptions of the risk of marijuana use and therefore did not mediate the relationship between city MMDs and adolescent marijuana use. However, a trend analysis using a difference-in-difference approach revealed a significant decline in the prevalence of lifetime marijuana use among City of Los Angeles high school students after Proposition D (a voter-approved ballot measure that outlawed over two thirds of the dispensaries in the city) was implemented in 2013. Dispensary bans were also significantly correlated with a longer distance between high schools and unlicensed dispensaries and a lower number of dispensaries located with 2,000 feet of participants’ high schools, factors which were in turn associated with less lifetime and recent marijuana use among students. Accounting for these factors strengthened the association between dispensary bans and student marijuana use but not to the point of statistical significance. The positive correlation between the number of licensed dispensaries located within 2,000 feet of high schools and a greater prevalence of lifetime marijuana use among students was statistically significant, but the positive correlation with recent marijuana use was not and the number of dispensaries located near schools was not a significant mediator of the negative association between dispensary bans and student marijuana use.

In a cross-sectional analysis using data from 57 LA County cities during the 2015/2016 and 2016/2017 school years, dispensary bans were negatively, not but significantly correlated with lifetime or recent marijuana use among students, which negated my focal hypothesis that MMD bans would have a significant suppressing effect on adolescent marijuana use in cities where they were enacted. This study did confirm, however, that enacting more restrictive dispensary policies can have a significant preventative impact on high school students’ marijuana use over time when followed by a committed enforcement effort as was seen in the City of Los Angeles with implementation of Proposition D. This research has also identified neighborhood and enforcement factors that are significantly associated with high school students’ marijuana use, such as how far unlicensed dispensaries are located from their school and/or how many unlicensed dispensaries were located near their school. Based on these findings, the primary conclusion of this dissertation is that regardless of whether a city chooses to ban or to allow dispensaries, rigorous enforcement of restrictions on their number and location is essential to prevent adolescent marijuana use.

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