Prevalence of Marijuana and other Substance use before and after Washington State's Change from Legal Medical Marijuana to Legal Medical and Nonmedical Marijuana: Cohort Comparisons in a Sample of Adolescents

Abstract

Background A growing number of states have new legislation extending prior legalization of medical marijuana by allowing non-medical marijuana use for adults. The potential influence of this change in legislation on adolescent marijuana and other substance use (e.g., spillover or substitution effects) is uncertain. We capitalize on an ongoing study to explore the prevalence of marijuana and other substance use in two cohorts of adolescents who experienced the non-medical marijuana law change in Washington State at different ages. Method Participants were 8th graders enrolled in targeted Tacoma, Washington public schools and recruited in two consecutive annual cohorts. The analysis sample was 238 students who completed a baseline survey in the 8th grade and a follow-up survey after the 9th grade. Between the two assessments, the second cohort experienced the Washington State non-medical marijuana law change, whereas the first cohort did not. Self-report survey data on lifetime and past month marijuana, cigarette, and alcohol use were collected. Results Multivariate multilevel modeling showed that cohort differences in the likelihood of marijuana use were significantly different from those for cigarette and alcohol use at follow-up (adjusting for baseline substance initiation). Marijuana use was higher for the second cohort than the first cohort, but this difference was not statistically significant. Rates of cigarette and alcohol use were slightly lower in the second cohort than in the first cohort. Conclusions This exploratory study found that marijuana use was more prevalent among teens shortly after the transition from medical marijuana legalization only to medical and non-medical marijuana legalization, although the difference between cohorts was not statistically significant. The findings also provided some evidence of substitution effects. The analytic technique used here may be useful for examining potential long-term effects of non-medical marijuana laws on adolescent marijuana use and substitution or spillover effects in future studies.

Simultaneous Alcohol and Marijuana Use Among College Students: Patterns, Correlates, Norms, and Consequences

“…Whereas a higher percentage of students at School C (52%), compared with School B (47%) and School A (36%), reported very easy access to marijuana, access did not appear to account for the school differences found. Evidence is mixed with regard to the effects of state policy‐related changes on marijuana use, attitudes regarding risk and acceptability, and norms (Blevins et al., ; Lynne‐Landsman et al., ; Mason et al., ). Students at School B perceived higher norms for SAM use among same‐gender peers and close friends compared with students at the other 2 schools, suggesting that the normative environment of a campus, which is affected by everything from perceived harm to enforcement of policies and laws on campus, may be more important for SAM use than the state's legal environment.…”

Cannabis and Mood Disorders

“…However, there are some negative effects that are critical to consider with widespread legalization, including the impact upon adolescents and people with psychiatric illnesses such as mood disorders. There is evidence demonstrating increased adolescent cannabis use [2] and increased cannabis use disorder (CUD) diagnoses [1*] in states that have legalized recreational cannabis. Furthermore, relatively little is known about the burden of problematic cannabis use on vulnerable populations such as the mentally ill and adolescents.…”

Support for marijuana legalization in the US state of Washington has continued to increase through 2016

“…The legalization of recreational marijuana sales and use has become a highly debated policy topic in recent years, especially in the US, although scientific research on the effects of these policies is very limited (Kim et al, 2016; Mason et al, 2016). Still, support for legalization of recreational marijuana continues to increase across the United States and globally (Cruz et al, 2016; Galston and Dionne, 2013).…”