Since California has progressive tobacco control policies and recent legalization of marijuana, data on co-use of tobacco and marijuana among AYA in this state would provide evidence from a unique regulatory environment that is likely to represent where the rest of the country may be headed. Using three school-based convenience samples of California AYA , we aimed to examine the patterns of past 30-day co-use of tobacco and marijuana products , and the product-specific associations between past 30-day use of these substances. Since the original surveys varied in questionnaires and methodologies, three samples were analyzed separately using the same analytic procedures. Only participants with complete data on past 30-day use of all tobacco and marijuana products were included in the analyses. Unweighted frequencies and proportions were computed for each tobacco and marijuana product. A cross tab of past 30-day use of tobacco and marijuana products was used to describe frequencies and proportions of past 30-day co-use patterns. To examine product-specific associations, a multi-variable logistic regression model for each marijuana product included all tobacco products and demographic variables . Estimates of each product specific association from individual samples were then combined by a pooling procedure for analysis of multiple studies using the command “metan” in STATA 15.0. All tests of hypotheses were two-tailed with a significance level of α less than 0.05.Table 2 presents proportions of co-use patterns of specific tobacco and marijuana products in the total samples.
For tobacco, e-cigarettes and cigarettes were the most commonly used products, while cigars were the least used product. Regarding marijuana,ebb flow table the combustible form was used the most, while the vaporized form was used the least. The most common couse patterns in all three samples were combinations of e-cigarettes or cigarettes and combustible marijuana . Figure 1 displays each of marijuana products used among only past-30-day tobacco users and vice versa. Across the three samples, 76.5%, 61.1%, and 70.8% of past 30-day tobacco users were using any marijuana product. On the other hand, 41.8%, 42.9%, and 32.4% of past 30-day marijuana users were using any tobacco product. Using 2016–2017 data from three demographically diverse California samples totaling 4,893 adolescents and young adults, we found that past 30-day co-use of tobacco and marijuana was common, with AYA using numerous different combinations of these substances. More importantly, those who used each tobacco product were more likely to use some or all marijuana products . Notably, co-use of tobacco and marijuana in our samples was consistently higher than use of tobacco only, but less than use of marijuana only. This finding differs from previous studies, which found that either co-use was more prevalent than single substance use among youth during 2009–2014,or that co-use was more prevalent than marijuana-only use but less than tobacco-use only among young adults during 2014–2015.It should be noted that national data from these studies were from an earlier time period, and therefore may not capture the changes and secular trend in co-use or tobacco and marijuana products.
In addition, there are regional variations in tobacco and marijuana regulations, and the findings from our California samples may reflect a unique regulatory environment with strong tobacco control policies but more marijuana normalization.Indeed, proportions of tobacco use across all our samples was less than national estimates, and proportions of marijuana use was higher than those reported from national surveys.Therefore, more research in other states is needed to unfold national average estimates of co-use. Although our study focused on the co-use of marijuana and tobacco, we found an interesting result that the use of a single-tobacco product was more prevalent than the use of multiple tobacco products, while the poly-marijuana use was more popular than the use of a single marijuana product. While the popularity of poly-marijuana use is consistent with prior research,the predominance of single-tobacco use seems in opposition to that reported previously.National data have documented that e-cigarette use has been the most commonly used tobacco products among adolescents since 2014.Since our data were collected during 2016–2017, we did find that exclusive e-cigarette use was the most common tobacco use pattern, which may reflect the recent transformation of tobacco use patterns among AYAs. Our study stands out by characterizing co-use in light of specific products for both tobacco and marijuana, notably the inclusion of under-studied forms of marijuana . We found that combinations of e-cigarettes or cigarettes and combustible marijuana were the most common patterns of co-use. This result is not surprising given the popularity of these products found in our samples, as well as in other national and state data. In addition to these common patterns, we also found that the co-use happened in all combinations across the spectrum of tobacco and marijuana products, including alternative or less common forms of two substances.
Regarding product specific associations, current use of each specific tobacco product was positively associated with some or all of the marijuana products in our study. This finding is in line with several recent studies,suggesting that not only popular forms of tobacco but also alternative forms increase the use of marijuana among AYA. However, the associations between hookah and vaporized marijuana and between cigar and combustible marijuana were not statistically significant. Since our samples were school-based convenience samples, these non-significant associations may be due to sample features. For example, small numbers of hookah and cigar users may limit our power to examine these associations. Additionally, small proportions of Black AYA may impact our findings related to cigars, since this subgroup is more likely to use cigars.More representative data are warranted to replicate our findings. While the current literature provides reasons for co-use of tobacco and marijuana in general, it may also help to explain co-use of specific products. Existing research revealed that the same routes of administration and the similarities in product appearance may explain the crossover between combustible and vaporized forms of these substances.A qualitative study among young adults also described distinct reasons for co-use depending on the type of tobacco products used with combustible marijuana. For example, cigarettes were used with marijuana to enhance the synergistic effects ,hydroponic grow table hookah was used with marijuana in most social settings , e-cigarettes were mainly used as a substitution or a means of lessening marijuana use, and cigars were used to roll blunts.Collectively, specific products should be considered in both research and practice of substance use prevention. The exponential growth of emerging tobacco products among adolescents coupled with the increasing legalization of marijuana nationwide make studying co-use of tobacco and marijuana a timely issue.This issue is even more important for California since the state is considered as the largest marijuana market in the US.Furthermore, the 2018 state report indicated that approximately 790,000 California adolescents had reported past-30 day co-use of tobacco and marijuana.The prevalence of marijuana use and co-use with tobacco may be partly due to AYA’s perceptions of harm related to marijuana and tobacco products.Marijuana is widely viewed as harmless or even good for health, and consistently perceived as more socially acceptable and less risky than tobacco.Moreover, AYA perceive a risk gradient with respect to tobacco, with cigarettes rated as most risky, followed by cigars and chew, with hookah and e-cigarettes rated as least risky. Given our finding that co-use was more prevalent than tobacco-only use, educational programs and interventions should address perceptions related to both tobacco and marijuana products to reduce the use of both substances among AYA.This study is subject to several limitations. Since our samples were school-based convenience samples, the findings may not be representative of the California AYA population.
The findings may not generalize to other states that have fewer tobacco control policies and less marijuana normalization than California. We could not establish causal relationships between tobacco and marijuana use due to the cross-sectional design. Additionally, our self-reported data were not biochemically verified and did not include information on several uncommon products . Finally, due to our measures of past-30-day use, we were unable to assess temporal specificity of co-use, such as use of tobacco and marijuana products at the same time or sequentially on the same occasion. Marijuana is one of the most widely used psychoactive substances, with an estimated annual prevalence of 3.8% of the global population age 15-65 who reported marijuana use in the past year . In the United States, there were 23.9 million current marijuana users in 2016 , and epidemiological trends show an increase of marijuana use in recent years . A national survey showed that anxiety, depression, and paranoia were associated with the use of marijuana . Stress is also a common problem reported by marijuana users . Moreover, these co-occurring problems may be interrelated. For example, a study by Ketcherside and Filbey indicated that among heavy marijuana users, perceived stress is associated with depression and anxiety symptoms, which in turn affected problematic marijuana use. Marijuana users have more adverse physical conditions than non-users. For example, sleep disturbance and poor appetite are frequently observed among individuals experiencing marijuana withdrawal symptoms . Impairment in respiratory function, as seen with tobacco smoking, is also associated with marijuana use , but a causal relationship is not clear . Additionally, pain is a common physical problem among marijuana users, and potential analgesic properties of marijuana have been explored in prior studies. A nationally representative survey demonstrated that chronic pain was significantly associated with an increased risk of marijuana use , which may be related to pain relieving compounds in marijuana . Quality of life assessments are important in evaluating treatment for substance use disorders as they focus on perceived functioning and well-being . Health related quality of life focuses on perceived satisfaction and functioning in both mental and physical health domains . A previous study suggested improved HRQoL with abstinence and lower marijuana use frequency . In contrast, a longitudinal study demonstrated that reduction in marijuana use was not associated with improvement in HRQoL . In a recent meta-analysis, it was reported that heavy marijuana use was linked with poorer HRQoL, but the association was inconsistent across studies and the quality of included studies was determined to be low . Furthermore, a prospective epidemiological survey revealed that marijuana use significantly affected mental, but not physical domains of HRQoL . In sum, findings regarding the relationship between marijuana use and HRQoL are mixed, and this relationship may be different for the mental versus physical domains of HRQoL. The inconsistent relationship between marijuana use frequency and HRQoL could be due to several reasons. First, factors influencing mental and physical domains of HRQoL could be different, so separate analyses may be preferable to explore the relationships. Second,marijuana use affects HRQoL via the severity of problems experienced by users. Frequent marijuana use increases the likelihood of developing marijuana-associated problems. Some users will subsequently develop related problems, such as diminished life satisfaction and achievement and problems with social activities . However, others may use marijuana without similar harms because problems do not occur immediately and may develop over time. Assessments of the relationship between marijuana use frequency and HRQoL may need to consider marijuana-related problems as perceived by the users, as well as separately consider the impacts of mental health symptoms and physical health conditions on HRQoL. It is important for treatment to not only target marijuana use reduction or abstinence, but to also address problems associated with marijuana and assess changes in perceived problems over time in order to fully evaluate the effectiveness of treatment. This knowledge may contribute to more tailored interventions provided by clinicians when treating problematic marijuana use. The present study investigates if marijuana-related problems mediates the relationship between marijuana use and HRQoL separately for mental and physical domains. Additionally, mental and physical symptoms were separately controlled for in the respective analyses due to the aforementioned issue that marijuana use often co-occurs with mental health symptoms and worse physical conditions, both of which could influence the respective HRQoL . A cross-sectional survey was designed to explore functional outcomes associated with reduction in marijuana use. This survey was conducted among participants with a history of marijuana use recruited from substance use disorder treatment programs and the general community in Los Angeles between April 2017 and February 2018.