Changes in Modes of Marijuana Consumption Among Colorado High School Students after Recreational Marijuana Legalization: Differences By Sex, Race, and Grade

Background: Emerging modes of marijuana use tend to be high potency (dabs) or have delayed effects (edibles). With changes in recreational marijuana laws, these modes may be increasingly available to adolescents, leading to potential acute overconsumption or an increase in risk of later dependence. This study aimed to assess differences in usual mode of marijuana consumption before and after recreational marijuana legalization (RML) by sex, race, and grade level among adolescents who report past 30-day marijuana use, and the association between these demographic characteristics and any mode of consumption.

Methods: Data come from the Healthy Kids Colorado Survey (HKCS), a biennial cross-sectional survey completed by high school students attending public and alternative schools in Colorado. High school students who reported past 30-day marijuana use in 2013 (n=2,792) and 2015 (n=1,644) were included in the study sample. Prevalence estimates for usual mode and any mode of marijuana in the past 30 days stratified by sex, race, and grade were calculated. Rao-Scott Chi-Square and multivariate logistic regression models were used to assess differences across years and by sex, race, and grade.

Results: Overall, the prevalence of students reporting ingestion as the usual mode of consumption decreased from 4.7% pre-RML to 2.1% post-RML, while dabbing and "other" as the usual mode increased from 4.0% to 6.0%. Post-RML, males were more likely than females to use all modes other than smoking in the past 30 days. Males were also more likely to use multiple modes (aPR=1.3, 95% CI:1.1, 1.4). Hispanic students were more likely than White students to report only using one mode (aPR=1.2, 95% CI:1.1, 1.3). Multi-racial students were more likely to report any ingestion (aPR=1.5, 95%CI:1.1, 1.8) and "other" modes (aPR=3.1, 95% CI:1.5, 5.9) compared to White students. Older students were more likely to report dabbing in the past 30 days compared to those in 9th grade (10th grade: aPR=2.2, 95% CI:1.6-2.9; 11th grade: aPR=1.7, 95% CI:1.2-2.4; 12th grade: aPR=1.8, 95% CI:1.2-2.5). The prevalence of all other modes of use, usual mode, and using multiple modes did not differ by grade level after RML (p>0.05).

Conclusions: Among Colorado high school students who currently use marijuana, past month mode of consumption differed by sex, race, and grade. Differences in usual mode of consumption were also present comparing years before and after the implementation of legalized recreational marijuana. Because of potential health consequences, further surveillance of modes of marijuana consumption among adolescents, particularly with dabbing, is needed, as marijuana policies continue to evolve.