Background The potential for increases in adolescent marijuana use is an important concern given recent changes in marijuana policy. The purpose of this study was to estimate trends in marijuana use from 1999-2013 among a national sample of US high school students. We examine changes over time by race/ethnicity and sex. Methods Data are from the National Youth Risk Behavior Survey (YRBS), which involves biennial, school-based surveys that generate nationally-representative data about 9th-12th grade students in the United States. Students self-reported sex, race/ethnicity, and marijuana use (i.e., lifetime use, current use, any use before age 13). We generated national estimates of the prevalence of marijuana use for the time period, and also tested for linear and quadratic trends (n=115,379). Results The prevalence of lifetime marijuana use decreased modestly from 1999 to 2009 (44% to 37%), and has increased slightly since 2009 (41%). Other marijuana use variables (e.g., past 30-day use) followed a similar pattern over time. The prevalence of past 30-day use from 1999-2013 for all groups and both sexes was 22.5%, and it was lowest among Asians and highest among American Indian/Alaska Natives. Although boys have historically had a higher prevalence of marijuana use, results indicate that male-female differences in marijuana use decreased over time. Conclusion Despite considerable changes in state marijuana policies over the past 15 years, marijuana use among high school students has largely declined. Continued surveillance is needed to assess the impact of policy changes on adolescent marijuana use.

Participation in MMJ programs varies considerably by state and within states over time. Trends are discussed within the context of federal and state policies, and the availability of marijuana via dispensaries.

Background In most of the world, cannabis smokers mix loose tobacco inside a joint, pipe, spliff, or cone. More recently, a ‘blunt’ formulation combines these two drugs by inserting cannabis into a hollowed-out cigar. Epidemiological research linking simultaneous use of these two drugs and the development of cannabis use disorders (CUD) remains unclear. This study estimates associations linking blunt smoking with levels and subtypes of cannabis problems. Methods Cross-sectional data on 27,767 past-year cannabis users were analyzed from the US National Survey on Drug Use and Health (NSDUH) conducted from 2009–2012. Ten self-reported items of DSM-IV CUD features elicited a single latent trait of cannabis problem (CP) severity, which was then regressed on past-year blunt smoking and past-month blunt frequency measures within the context of a conceptual model. Differential item functioning (DIF) analysis evaluated potential bias in CP feature response by blunt smoking history. Results Past-year blunt smoking was associated with higher CP severity compared to cannabis users who did not smoke blunts. Days of blunt smoking in the past month also predicted higher CP severity than less frequent blunt use. Those smoking blunts experienced more subjectively felt tolerance and having spent more time obtaining or using cannabis, but were less likely to experience other problems, even at the same level of CP severity. Conclusions These findings suggest smoking blunts might promote the development of problematic cannabis use. Responses to cannabis problems differed by history of blunt smoking, possibly implicating an influence of tobacco on measurement of cannabis use disorders.

Early-onset cannabis use is widespread in many countries and might cause later onset of depression. Sound epidemiologic data across countries are missing. The authors estimated the suspected causal association that links early-onset (age <17 years) cannabis use with later-onset (age > or =17 years) risk of a depression spell, using data on 85,088 subjects from 17 countries participating in the population-based World Health Organization World Mental Health Survey Initiative (2001-2005). In all surveys, multistage household probability samples were evaluated with a fully structured diagnostic interview for assessment of psychiatric conditions. The association between early-onset cannabis use and later risk of a depression spell was studied using conditional logistic regression with local area matching of cases and controls, controlling for sex, age, tobacco use, and other mental health problems. The overall association was modest (controlled for sex and age, risk ratio = 1.5, 95% confidence interval: 1.4, 1.7), was statistically robust in 5 countries, and showed no sex difference. The association did not change appreciably with statistical adjustment for mental health problems, except for childhood conduct problems, which reduced the association to nonsignificance. This study did not allow differentiation of levels of cannabis use; this issue deserves consideration in future research.

ABSTRACT. Objective: The purpose of this study was to assess the prevalence of modes of marijuana consumption among Colorado youth and explore variation by demographics, access, substance use, and risk perceptions. Method: Data are from a 2013 survey of Colorado high school students (N = 25,197; 50.5% female). The outcome variable was usual mode of marijuana consumption (i.e., smoking, vaporizing, ingesting edibles, or other) among those reporting past 30-day marijuana use. Classification variables included sex, grade level, race/ethnicity, sexual orientation, current alcohol and cigarette use, frequent marijuana use, early marijuana use (<13 years), perceived harmfulness, and perceived wrongfulness. We calculated prevalence estimates overall and by the variables listed above, and also conducted multinomial logistic regression models. Results: Findings indicate that 15% of Colorado high school students who use marijuana report that they usually use a mode of consumption other than smoking. Among students reporting past 30-day marijuana use, 85% said smoking was their usual mode of consumption. The remainder reported that their usual mode of consumption was vaporizing (6%), ingesting edibles (5%), or another method (4%). Boys, Whites, Asians, and 12th graders were the most likely to report vaporizing. High perceived harmfulness was associated with vaporizing or ingesting edibles. Conclusions: The majority of Colorado youth who use marijuana usually smoke it. Youth may be using vaporizers and ingesting edibles as a way to reduce the harm associated with inhaling combusted smoke. (J.