We also adjusted for the current use of each of these products/substances to address the potential confounding in all the models except for any use of the three. For example, we coadjusted for the use of e-cigarettes and marijuana in the model regressing the odds of using cigarettes. A jackknife method based on design-based replicate weights was used to estimate variances and significance values of regression coefficients. The same types of analyses were conducted separately for use of different types of products/substances. All analyses were implemented using SAS 9.4 . In 2018, 1.66 million California young adults, ages 18 to 25, were currently using at least one form of cigarette, e-cigarette, or marijuana: 314,000 smoked cigarettes, 682,000 used e-cigarettes, and 1.3 million used marijuana. There was no statistically significant change in cigarette use between 2017 and 2018 . In contrast, there was escalating use of e-cigarettes and marijuana. Between 2017 and 2018, current e-cigarette use climbed by 4.8% and current marijuana use rose by 4.6% among young adults. The proportion of young adults currently using any of these products/substance increased by 5.5% between 2017 and 2018 . Table 1 presents descriptive analyses of the current use of cigarettes, e-cigarettes, marijuana, and any use of the three by age, gender, race/ ethnicity, income , psychological distress, urban/ rural residence, and region of residence. Young adults aged 18–20 were smoking cigarettes at significantly lower rates than other young adults aged 21–25 . Underage use was substantial for e-cigarettes and marijuana. About 17% of underage young adults were current e-cigarette users. About 27% of underage young adults were current marijuana users. A wide and significant male–female difference was seen in e-cigarette use , vertical farming system with male e-cigarette use nearly doubled female e-cigarette use. Any use of cigarettes, e-cigarettes, or marijuana was also significantly higher for males than females.
Young adults who were white have higher rates of cigarette and e-cigarette use than those who were Latino. Approximately 27% of young adult Latino, whites, and Asians used marijuana. Only e-cigarette rates differed significantly by income: young adults with incomes at or below 200% FPL- used e-cigarettes at lower rates than young adults with incomes greater than 200% FPL. Young adults with psychological distress had higher rates of use of cigarettes, e-cigarettes, marijuana, or any use of the three.From 2017 to 2018, California saw an increase in e-cigarette and marijuana use among young adults, while cigarette smoking remained flat. Psychological distress was observed to be associated with cigarette, e-cigarette, marijuana use, or any use of the three. Using cigarettes, ecigarettes and marijuana were also found mutually correlated. California’s trends in cigarette and e-cigarette smoking are parallel to those observed nationwide . What stands out in our findings are several aspects. One is that the percentage of California young adults using marijuana increased to 28.5% from 2017 to 2018 while the national rate remained to be 22% for both years Another finding is that in 2018, those young adults who were using each of these products/substance also significantly increased the odds of using cigarettes, e-cigarettes, or marijuana than their counterparts. Importantly, we found that severe psychological distress was significantly associated with the use of cigarettes and marijuana. Although many tobaccos and recreational cannabis use policies restrict sales to young adults under age 21, underage use is considerable– about half of the young adults were current e-cigarette users and more than half a million or 40% of current marijuana users were underage. Our findings that cigarette smoking rates remained flat between 2017 and 2018, but e-cigarette smoking and marijuana increased could be possibly explained by the current policy changes related to the cigarette tax increase and recreational marijuana legalization in California.
The finding that the smoking rates would remain flat is expected since the CHIS 2017 data were collected after the cigarette tax increase in April 2017. Studies have found that marijuana policy could inadvertently affect cigarette and marijuana use and this spillover effect poses challenges to tobacco cessation . Similar to our findings, other studies have also shown that cannabis and e-cigarettes uses have increased among youth, and these trends will likely continue as e-cigarettes remain to gain popularity and cannabis legalization policies proliferate . Our findings that the use of tobacco is positively associated with the use of marijuana or vice versa among young adults are consistent with other studies . There are several explanations for this association. One is that tobacco and marijuana use support and reinforce the use of each other Research has shown that tobacco use is associated with initiation and dependence on other substances, such as marijuana . Longitudinal studies that examined tobacco use before marijuana use generally supported a gateway sequence and progression, in that case, people smoked tobacco first, then marijuana . Additional studies have shown a “reverse gateway effect,” that those who used marijuana were at increased risk of initiating tobacco . Another explanation for the concurrent use of cigarettes, e-cigarettes and marijuana is that tobacco and marijuana use can co-occur via the same devices for both tobacco and marijuana . Studies showed that concurrent users were more likely to use e-cigarettes and blunts to administer marijuana. Vaporizers are increasingly popular among young people. Many youths replace nicotine with marijuana in battery-powered vaporizers . Another way is through the use of “blunts,” or rolling up marijuana in a cigar or cigarillo shell. Research has shown that ’smoking’ was found to constitute a social construct within which the use of cigarettes, cigars, and blunts was somewhat interchangeable among the youth . Tobacco and marijuana, taken in combination, potentially raise the likelihood of dependence on these substances and problems associated with their use.
For example, one study of University of Florida college students who used both cigarettes and marijuana found that 65% had smoked both substances in the same hour; 31% reported they smoked tobacco to prolong and sustain the effects of marijuana, and 55% had friends who engaged in these behaviors . Our findings that psychological distress was significantly associated with smoking cigarettes or using marijuana were supported by previous studies . Studies showed that adolescents and young adults with mental health problems were at high risk for tobacco and marijuana use, compared to those without such problems . Studies also showed that affective disorders and psychological distress were more common among those who smoke than those who do not smoke and among cannabis-dependent participants . Daily cannabis use was significantly more common among persons with serious psychological distress and was increasing in this group, as well as among those without . Lower quit rates among those with serious psychological distress are one factor that could contribute to the higher prevalence of smoking in this group . A study using the 2008–2016 National Survey on Drug Use and Health showed that quit rates among individuals with past-month psychological distress were approximately half than quit rates of those without psychological distress and had not increased over the past decade . Adults with depression or psychological distress had a lower quit ratio overall,vertical farming racks but were equally or even more likely to make quit or self-regulation attempts . One study’s findings suggest an increase in psychological distress among those who smoke over time may be due to the fact that as smoking has declined, thus those with psychological distress are comprising a greater proportion of those remaining to smoke. . Given that our study is cross-sectional, the direction of the association between substance use and mental health could not be established. If substance use is an antecedent to psychological distress, our estimated effects of psychological distress on smoking cigarettes and marijuana use may be biased upward. A few longitudinal studies provide causal evidence that smoking or marijuana use increased with psychological distress. For instance, a study using longitudinal data showed that smoking uptake was associated with an increase in psychological distress . Another birth cohort study that tracks youth longitudinally from before marijuana onset also reinforced that early-onset and chronic marijuana use was associated with a greater risk of psychiatric disorders . Data from a cohort study with an 8-year follow-up in the general population in Stockholm County also showed cannabis use was associated with an increased risk of psychological distress eight years later in Sweden women .
Regardless of the causal direction, to protect the health and well-being of young adults, decision-makers need to consider both the mental health and substance use behavior implications of less restrictive substance use policies. California laws banned sales of cigarettes, e-cigarettes in 2016, and marijuana to young adults under 21 years old. Though underage young adults had lower odds of smoking cigarettes than older young adults, the underage use was substantial for e-cigarettes and marijuana.The studies did show that California law reduced illegal sales to youth under 18 . Researchers from UC Davis used data from the 2012–2019 Behavioral Risk Factor Surveillance System and observed that although the trends of ever and current smoking did not change significantly before and after California’s T21 policy, while there was an 8% annual decrease of daily smoking before the policy and a 26% annual decrease after the policy among underage in California . Our study and others showed that underage use could still be an issue due to limited knowledge of such laws and other influencing factors . A study found that the knowledge of the minimum legal age was inversely associated with the intention to use tobacco among youth. Educational campaigns to raise awareness and support for MLA among youth may improve the impact of MLA policies . The strength of this study is that it is based on CHIS data, which is the largest state health survey in the nation, and it collects extensive information for assessing the health and health behaviors of adults, adolescents, and children in California. Each year, CHIS surveys over 20,000 households. Also, from 2016 to January 2018, California implemented a series of policies, including prohibiting the sale of tobacco products and e-cigarettes to persons under 21, a cigarette tax increase, and recreational marijuana legalization. All these state-level policy changes make California a natural experimental ground for studies on tobacco and marijuana use behaviors and risk factors associated with smoking behaviors among young adults. It is worth noting that the findings in this study are subject to some limitations. First, data were self-reported, which might have resulted in recall and social desirability biases. Specifically, we were unable to examine whether decriminalization and legalization of adult marijuana use affected self-reporting bias; that is, respondents might have felt more comfortable reporting marijuana use as it became legal in California. Second, the survey does not include institutionalized populations and persons in the military in its sample, so the results might not be generalizable to those populations. Lastly, as noted, it is based on cross-sectional data, it is difficult to determine the direction of the relationships we estimated, for instance, if cigarette use caused marijuana use or vice versa. The adverse consequences of illicit drug use on users’ physical and psychological health have been examined extensively. Substance abuse has been found to be associated with reduced cognitive abilities , educational attainment , as well as undesirable labor market outcomes such as unemployment , employment mobility and lower wages . Studies that specifically focus on marijuana-use and labor market outcomes have yielded similar findings , where regular cannabis use is associated with poor school performance, higher dropout rates , and lower levels of educational attainment – an important factor that facilitates subsequent labor market outcomes including occupational status and income . Despite the growing number of studies investigating the relationship between substance abuse and labor market outcomes, however, a closer examination of the empirical evidence reveals a surprising lack of concurrence among their findings. Using data from both the 1980 and 1984 waves of the National Longitudinal Survey of Youth , Gill & Michaels , examine the effects of substance abuse on wages. After accounting for what they refer to as “self-selection” effects, the authors conclude that users of illicit drugs receive higher wages than their non-drug using counterparts.