Limiting consideration to respondents who reported past-30-day marijuana use and adjusting for complex survey design, sampleweighted multivariable logistic regressions estimated associations between a binary indicator for respondents’ selection of vaping as their primary mode of use and indicators for state marijuana policies at the respondent’s interview date. Covariates adjusted for interview year to capture national time trends in product choice/availability, census region to capture time-invariant regional differences in attitudes towards marijuana use and access, and respondent sociodemographics . Sensitivity checks added three binary covariates for MM-only laws that allowed home cultivation, that had operational dispensaries, and that forbade smoking as a mode of use. Robustness checks repeated these analyses with a vaping-or-dabbing indicator as the outcome variable.Yale University’s IRB deemed this study exempt from review . This study is the first to show a relationship between MM policy attributes and EVALI. It also replicates prior findings on the relationship between RM and EVALI : states that legalized RM by August 1, 2019 had a lower EVALI incidence. Given that EVALI cases stemmed primarily from informally-sourced vaporizable marijuana concentrates, these results are consistent with crowd-out, whereby introduction of one market displaces utilization of another . Simply put, if the public can obtain products legally from reputable sources, there is less demand for illicit market products. Thus, RM legalization could have dampened market penetration of tainted marijuana concentrates by reducing consumption of informally-sourced marijuana products more generally.
Findings for MM legalization, however, were more nuanced: among states with MM only, laws allowing home cultivation were associated with fewer EVALI cases relative to those prohibiting it. This might be expected if home cultivation increases the availability of marijuana flower while decreasing reliance on commercial marijuana markets, reducing exposure when tainted marijuana concentrates are introduced. Specifically, patients and caregivers who can grow their entire grow cannabis supply at home would be less likely to consume illicit market products. The resulting reduction in demand for marijuana flower on the illicit market should depress its price, such that individuals who continue to rely on the illicit market face financial incentives to consume flower over vaping concentrates, based on the change in their relative prices. Both of these effects—directly on MM patients’ and caregivers’ likelihood of exposure to tainted products and, via price, on product choice among consumers who remain in the informal market—should reduce exposure to tainted marijuana concentrates. An additional policy attribute, prohibitions on smoking as a mode of MM use, was also associated with increases in hospitalized EVALI cases when excluding states that had this policy attribute but allowed sales of marijuana flower, effectively enabling combustible use. This might be explained by impacts on mode of use. Specifically, given that vaping is the second most popular mode of marijuana consumption after smoking , restrictions on combustible use could lead to increased use of vaporizable marijuana. For MM patients, this could occur via both new MM users initiating with vaporizable marijuanaproducts and established MM users switching from smoking to vaping. Effects could also extend to non-medical users if consumers interpret the prohibition as a signal that vaporizable marijuana products are safer or switch to vaping as a means to evade detection of illicit use. Indeed, devices used to vaporize marijuana concentrates are often indistinguishable from nicotine e-cigarettes and produce less odor than smoking marijuana, making them easier to conceal . Consequent increases in the share of people who vape concentrates would be expected to increase the number of EVALI cases when a contaminated product enters the informal market.
Among those living in MM-only states, allowing home cultivation was associated with reduced odds of reporting vaping as one’s primary mode of use, consistent with increased reliance on home cultivation and/or reduced prices of marijuana flower. Concurrently, operational dispensaries were associated with increased odds of vaping as the primary mode of use, consistent with increased access to marijuana concentrates as well as potential effects on perceptions of vaping marijuana as a safe mode of use. Further adjusting for MM-only states that prohibited combustible use found a positive but statistically non-significant association between this restriction and marijuana vaping , although limited power may have influenced the ability to detect a significant finding. Variation in MM policy attributes’ associations with both EVALI case counts and adults’ mode of marijuana use suggests that understanding the implications of such policy details is critical for informing marijuana regulatory decisions. Indeed, analyses suggest different relationships when using a single yes-no indicator of MM legalization versus adjusting for the laws’ policy attributes. These policy details may also be politically malleable: they can be modified via legislative amendments without requiring the full repeal of existing MM laws, which are often quite popular with the electorate . This study improves upon prior analyses of states’ marijuana policies and the prevalence of EVALI in three important ways. First, while others relied on binned case data , we used exact case counts, removing a potential source of bias . Second, we assessed the role of MM policy attributes in this relationship, revealing greater nuance in the MM-EVALI relationship by identifying specific policy details that may be consequential for EVALI and subject to amendment in established legislation. Third, we considered how these attributes related to adults’ self-reported mode of marijuana use to clarify the mechanism behind the MM-EVALI relationship. This study’s primary limitation was related to available data on marijuana vaping. BRFSS, the US’s only annual, state-representative adult dataset that asks about mode of marijuana use, did not field thisquestion in all states. Moreover, its wording did not clearly differentiate vaping indoor cannabis grow system concentrates from vaporizing marijuana flower . This distinction is critical: while vaping marijuana concentrates was implicated in EVALI, vaping flower was not. As even preEVALI analyses suggest that vaping marijuana flower poses lower health risks than vaping marijuana concentrates , future research will require nationally representative data that clearly distinguishes these modes of use. A second limitation was the potential for differences in case detection between states. Reassuringly, findings held when limiting consideration to hospitalized EVALI case counts, which state and local health departments regularly reported to the CDC over December 2019 and January 2020. Moreover, to drive this study’s results, case detection would have to have been systematically lower in states that legalized recreational marijuana use or medical use with home cultivation. It is not clear why that would be so. A third limitation was our inability to assess variation in recreational marijuana policy attributes.
Specifically, among the 10 states that implemented recreational marijuana legalization prior to 2020—excluding Washington DC, which was not in our data—none prohibited combustible use, only one forbade home cultivation , and three lacked recreational retailers as of August 1, 2019. Beyond concerns about generalizability and limited statistical power with variation based on so few states, none of those four states fielded the BRFSS marijuana module between 2016 and 2019, precluding estimation of RM policy attributes’ associations with mode of use. Thus, we leave consideration of recreational marijuana policy attributes to future work. Although this study’s findings are not causal, they provide direction to states that have passed or are considering MM legalization. Specifically, to the extent that such policies affect licit and illicit marijuana use, policymaking not only must ensure the safety of legal products but also should consider potential impacts on illicit market offerings. In particular, incentivizing or restricting a particular mode of marijuana use based on presumed or demonstrated health effects with unadulterated product may have unexpected consequences if the proposed “less harmful” mode of use involves a product that is more vulnerable to adulteration, as was likely the case for vaporizable marijuana concentrates during the 2019 EVALI outbreak. This is relevant to RM states as well, since youth who cannot purchase marijuana legally may turn to informal sources. To the extent that these findings reflect causal relationships, carefully-crafted marijuana legalization policies may provide a means to reduce the scope of future EVALI outbreaks, whether due to vitamin E acetate or other additives. More work is needed in this area, as the stakes for getting these policy details right are high: with over 17% of Americans ages 12-and-up reporting past-year marijuana use , population health depends on it. While rates of adolescent combustible tobacco product use have continued to decline in recent years , rates of noncombustible tobacco product ) use have risen in U.S. high school youth . In 2019, e-cigarettes were the most commonly used tobacco product by high school students with 27.5% reporting past 30-day use behavior . Rates of adolescent lifetime and current use of marijuana are also increasing among youth in the U.S. , with reported annual use rates of 36% in 12th grade students and 29% in 10th grade students in 2019 . Adolescents who use marijuana are at increased risk to initiate use of e-cigarettes and to be dual users of e-cigarettes and marijuana . Tobacco product use is a leading preventable cause of morbidity and mortality. There are known adverse health effects associated with ecigarette use including nicotine addiction, respiratory symptoms, asthma exacerbations, and e-cigarette or vaping product use associated lung injury. There is also concern that similar to individuals who smoke combustible tobacco products, individuals who use e-cigarettes may be at increased risk for cardiovascular disease . Further, individuals who use marijuana are at increased risk for respiratory illnesses such as asthma and also at increased risk for cardiovascular disease .
Obesity is also another leading preventable cause of morbidity and mortality. Rates of obesity in adolescents are 20.6% . Obesity in adolescents is also associated with adverse health consequences, some of which overlap with tobacco product- and marijuanarelated morbidity, including type 2 diabetes, hypertension, cardiovascular disease, and metabolic syndrome . Previous research indicates that adolescent males who are obese are at increased odds of using e-cigarettes compared to peers who are not obese , and that female adolescents who use substances including marijuana are at increased odds to be overweight or obese . Even though the association of substance use and obesity is complex, they share common risk factors. Particularly, use of e-cigarettes or marijuana is individually linked to increased appetite, reduced physical activity, and increased screen time, all of which contribute to excess weight. In addition, research evidence suggests dual use of ecigarettes and marijuana exacerbates the likelihood for risk behaviors compared to single or non-users.Given the rising rates of e-cigarette and marijuana dual use in adolescents and the potential associations with obesity, it is important to identify behaviors that may contribute to obesity in adolescents who use e-cigarettes and/ or marijuana. These behaviors include unhealthy diet and inadequate exercise patterns during childhood and adolescence which may continue throughout adulthood if not modified early . To evaluate this, we examined data from adolescents who participated in the 2017 Youth Risk Behavior Survey. To assess risk factors of obesity, we examined the associations of exclusive and dual use of ecigarettes and marijuana and the attainment of the “Let’s Go! 5–2-1–0” obesity prevention guidelines from the Maine Youth Collaborative . The ‘5–2-1-0’ recommendations have been used to screen and evaluate healthy behaviors in children in various settings and in research . These daily guidelines recommend that youth eat at least five servings of fruits and vegetables , view two hours or less of screen time , participate in at least one hour of physical activity , and consume zero sugar-sweetened beverages . We also assessed the associations between current e-cigarette and marijuana use and perceptions of weight status among adolescents. We hypothesized that compared to non-users of e-cigarettes and marijuana, exclusive e-cigarette users, exclusive marijuana users, and dual users of e-cigarettes and marijuana would be at reduced odds of meeting the ‘5–2-1-0’ recommendations and of perceiving themselves as slightly/ very overweight. Specific to current users only, we also hypothesized that dual users would be at decreased odds to meet these recommendations and perceive themselves as slightly/very overweight than exclusive users of either e-cigarettes or marijuana.