Tobacco and marijuana use among adolescents and young adults: A systematic review of their co-use
Highlights
► This review examined tobacco and marijuana co-use among youth and young adults. ► Most relationships (85%) between TOB and MJ use were significant. ► Ethnicity, health, and school factors were consistently associated with co-use. ► The only consistent consequence of co-use was exacerbation of psychiatric symptoms. ► Few studies examined prevention or cessation interventions for TOB and MJ co-use.
Introduction
Tobacco (TOB) use is the leading cause of preventable death and is estimated to kill more than 5 million people each year worldwide (World Health Organization, 2009). By the end of this century, TOB is projected to kill a billion people or more (Peto & Lopez, 2001). TOB use among teens and young adults is particularly important to address as more than 90% of U.S. adults who smoke became regular smokers before the age of 18 (U.S. Department of Health and Human Services, 1994). In 2009, 11% of U.S. adolescents and 42% of young adults aged 18–25 reported using a TOB product in the past month (Substance Abuse and Mental Health Services Administration, 2010). Throughout the world, nearly 20% of 13 to 15 year olds use some type of TOB product (Global Youth Tobacco Survey Collaborative Group, 2002). In order to reduce the health and societal impact of TOB use worldwide, it is important to understand factors that contribute to the onset and perpetuation of TOB use among young people. Further, TOB is relevant to adolescent and young adult health given its implication as a gateway drug to marijuana and other illicit drug use (Beenstock and Rahav, 2002, Bentler et al., 2002).
Marijuana (MJ) is the most commonly used illicit substance among youth and young adults, with approximately 7% of U.S. adolescents age 12 to 17 and 18% of those age 18 to 25 reporting MJ use in the past month in 2009 (Substance Abuse and Mental Health Services Administration, 2010). Rates for both age groups have increased since 2008, and are highest among young adults compared to any other age group.
There has been great interest in the relationship between TOB and MJ use among teens and young adults. Epidemiological data indicate that the co-use of TOB and MJ increased throughout the 1990s in Western countries (e.g., Choquet, Morin, Hassler, & Ledoux, 2004). Similarly, higher cigarette taxes are associated with lower likelihood of MJ use and frequency of use among adolescents in the U.S. (Farrelly, Bray, Zarkin, & Wendling, 2001). TOB and MJ, taken in combination, potentially raise the likelihood of dependence on these substances and problems associated with their use. For example, one study of college students at the University of Florida who used both cigarettes and MJ found that 65% had smoked both substances in the same hour; 31% reported they smoked TOB to prolong and sustain the effects of MJ; and 55% had friends who engaged in these behaviors (Tullis, DuPont, Frost-Pineda, & Gold, 2003).
As smoked substances, there is evidence that TOB and MJ use support and reinforce use of each other. One mechanism by which this may take place is through the use of “blunts,” or MJ rolled up in a cigar or cigarillo shell. Blunts are an increasingly common drug delivery device among middle and high-school age youth (Golub, Johnson, & Dunlap, 2005), and their use is associated with current cigarette and cigar usage (Soldz, Huyser, & Dorsey, 2003). Several studies have described TOB and MJ co-use through blunts. For example, Sifaneck, Johnson, and Dunlap (2005) describe “blunt chasing” – the smoking of a cigarillo or cigar following a blunt – as an emerging phenomenon that further expands the market for TOB products among blunt smokers, and explains how blunts can contribute to the likelihood of nicotine dependence among blunt users. Ethnographic studies of blunt use generally tend to support the notion that for some young people who use MJ, their MJ use supports and reinforces a TOB smoking habit (Amos et al., 2004, Highet, 2004, Lee et al., 2010), and that a substitution phenomenon often takes place between the two substances (Akre et al., 2009, Amos et al., 2004). In an ethnographic study of blunt users in New York City, Dunlap, Benoit, Sifaneck, and Johnson (2006) argued that the culture of blunt smoking (specifically the social aspects of the behavior) calls for a different construction of MJ dependence than current DSM-IV criteria. Interviews with blunt smokers revealed that some do perceive blunt use as “addictive,” and it tends to be the TOB rather than the MJ that contributes to the addictive process.
Viveros, Marco, and File (2006) reviewed the pharmacological processes underlying addiction to TOB and MJ, focusing on adolescent animal studies examining perpetuation of the use of both substances. Their review described systems that were mutually enhanced by the two substances (i.e., reinforcing effects, effects on anxiety-related behaviors) and those that have contrasting effects (i.e., food intake and cognition), suggesting that there is a complex relationship between the two substances. They concluded that “the joint consumption of nicotine and cannabis will [likely] enhance the rewarding effects of low doses” (p. 1174), and called for more human and animal studies in this area, particularly in sex differences in the interaction of TOB and MJ use.
While a number of studies have examined the association between TOB and MJ use both in North America and abroad, the consistency in findings have not been evaluated. In an effort to characterize the relationship between TOB and MJ use among teens and young adults, we present a systematic review of human studies in this area. Specifically, this paper summarizes the literature on TOB and MJ co-use including the relationship of co-use, correlates and consequences of co-use, and the success of interventions for prevention or cessation of co-use.
Section snippets
Method
Articles published in print or online between 1999 and 2009 were identified through computerized literature searches in two databases (PubMed, PsycINFO), published meta-analyses, review articles, and reference lists. Keyword search terms were: smoking, tobacco, nicotine, or cigarette, combined with marijuana or cannabis. Study title, abstracts, and bodies were reviewed by the first and second authors to determine study inclusion. Selection was restricted to English language publications with
Coding associations between TOB and MJ use
For studies examining co-use of TOB and MJ, relationships were summarized for cross-sectional and longitudinal studies separately. For studies that considered multiple use relationships, we considered each relationship separately. For example, if a study examined the association between past 30-day TOB and MJ use and also past 30-day TOB use and MJ dependence symptoms, we coded these as two separate relationships. The individual studies used a variety of statistical techniques to evaluate
Coding associations between correlates and consequences of co-use
For correlates and consequences of co-use, we computed “summary codes” for each category, to summarize the state of the literature for that category. The percentages refer to the number of associations supporting the expected association divided by the total number of associations for the category. Based on the percent of findings supporting the association, each category was classified using the following rules, consistent with Sallis et al. (2000): 0%–33% of analyses supporting a category = no
Coding prevention and intervention studies
Studies describing a prevention or cessation intervention were included if they directly measured TOB and MJ co-use among participants (i.e., not just the use of each substance independently in a sample). We coded each study by findings directly related to the co-use of TOB and MJ (+, −, ?, or 0) and calculated an overall summary rating for each category (prevention, intervention) as described above.
Results
PubMed yielded 1572 and PsycINFO yielded 1254 peer-reviewed studies with at least one TOB- and one MJ-related keyword. Of these 163 were directly relevant to concurrent use of TOB and MJ and had participants who were only adolescents or young adults (ages 13 to 25).
Epidemiology/use patterns
One hundred studies addressed the co-use of TOB and MJ in a cross-sectional or longitudinal design. We categorized these studies as 1) cross-sectional (n = 56); 2) cross-sectional time course (n = 10; retrospective assessment of the causal relationship between TOB and MJ use); and/or 3) longitudinal (n = 37; Table 1). The results of the review are summarized below. Table 1 summarizes the 169 total associations between TOB and MJ use for all cross-sectional and longitudinal studies reviewed. Across
TOB and MJ use among teens and young adults with mental health problems
Adolescents and young adults with mental health problems are at high risk for TOB and MJ co-use, as rates of both TOB (Ramsey, Brown, Strong, & Sales, 2002) and MJ (Roberts, Roberts, & Xing, 2007) use are higher in this population compared to those without such problems. Among teens and young adults with mental health problems, like the general population, there is a strong association between TOB and MJ use. We found eight studies that examined whether there was an association between TOB and
Simultaneous use
The issue of simultaneous TOB and MJ use has been recognized as important (Burns, Ivers, Lindorff, & Clough, 2000), especially since the drugs are one of the most common combinations among adolescents and young adults (Barrett, Darredeau, & Pihl, 2006). TOB and MJ co-use represents the second most common pattern of polydrug use among Bosnian adolescents (75%; Redzic, Licanin, & Krosnjar, 2003), and the third most common combination among Dutch adolescents, following co-use of alcohol with TOB
Predictors/correlates of TOB and MJ co-use
While there is a clear association between TOB and MJ use among adolescents and young adults, the factors associated with co-use are less well-identified. Over the past 10 years, a number of factors have been tested as possible correlates or predictors of TOB and MJ co-use. We found 25 individual studies, which examined 24 different predictors or correlates of TOB and MJ co-use, in six categories (genetic/environmental, demographics, individual mental and physical health, parenting
Consequences of TOB and MJ co-use
Most studies examining the long-term effects of TOB and MJ co-use have been conducted with adult samples, which were not included in the present review. The adult literature supports a substitution phenomenon between TOB and MJ, whereby reduction in use of one substance leads to an increase in use of the other substance (Copersino et al., 2006). Research on the consequences (both immediate and longer-term) of using both TOB and MJ in adolescence and young adulthood is growing (Table 4). Our
Prevention/intervention
Moving beyond descriptive studies is intervention research to prevent or treat TOB and MJ co-use associated problems. While a great many intervention studies have addressed the prevention and/or cessation of TOB, alcohol, and MJ use among teens and young adults, few interventions have directly addressed the co-use of TOB and MJ.
Prevention
Between 1999 and 2009, we found thirty-five peer-reviewed publications that addressed the prevention of both TOB and MJ use among teens and young adults. Of those, only three directly measured the co-use of TOB and MJ and all (100%) found significant effects on co-use (see Table 5). Trudeau, Spoth, Randall, and Azevedo (2007) found that the Iowa Strengthening Families Program, a family-focused universal preventive intervention, slowed the growth of polysubstance use (including TOB, MJ and other
Intervention
Between 1999 and 2009, eight studies described interventions that were designed to treat TOB and MJ use among teens and/or young adults. However, only two articles, describing the same trial of a one-session Motivational Interviewing intervention, directly measured the co-use of TOB and MJ, and initial findings were not sustained (Table 5). McCambridge and Strang (2004) reported that at termination of treatment, MJ reduction was greatest among heavy cigarette smokers; but these effects were
Discussion
We conducted a systematic review of the recent literature describing TOB and MJ co-use among adolescents and young adults. A large body of cross-sectional and longitudinal research globally has defined the basic relationship between TOB and MJ use in young people. Clearly, the use of one substance increases the likelihood of concurrent or future use of the other substance. Research efforts should turn to the more rarely studied areas of who is most likely to co-use TOB and MJ, how this co-use
Acknowledgments
This study was supported by an institutional training grant (T32 DA007250; PI, J. Sorensen), a center grant from the National Institute on Drug Abuse (P50 DA09253; PI, J. Guydish), and an individual Postdoctoral Fellowship Award from the California Tobacco-Related Diseases Research Program (18FT-0055; PI, D. Ramo). The preparation of this manuscript was supported in part by a career development award from NIDA (K23 DA018691; J. Prochaska, P.I.), a research project grant from the National
References (124)
- et al.
Tobacco and cannabis co-occurrence: Does route of administration matter?
Drug and Alcohol Dependence
(2009) - et al.
Correlates of cannabis initiation in a longitudinal sample of young women: The importance of peer influences
Prevention Medicine
(2007) - et al.
Transitions to regular smoking and to nicotine dependence in women using cannabis
Drug and Alcohol Dependence
(2008) - et al.
Prospective study of adolescent drug use among community samples of ADHD and non-ADHD participants
Journal of the American Academy of Child and Adolescent Psychiatry
(2006) - et al.
Association between early onset of cigarette, alcohol and cannabis use and later drug use patterns: An analysis of a survey in European metropolises
European Addiction Research
(2005) - et al.
Testing Gateway theory: Do cigarette prices affect illicit drug use?
Journal of Health Economics
(2002) - et al.
Transitions from first substance use to substance use disorders in adolescence: Is early onset associated with a rapid escalation?
Drug and Alcohol Dependence
(2009) - et al.
Marijuana use motives: concurrent relations to frequency of past 30-day use and anxiety sensitivity among young adult marijuana smokers
Addictive Behaviors
(2007) - et al.
Cannabis: A Trojan horse for nicotine?
Australian and New Zealand Journal of Public Health
(2000) - et al.
Is alcohol, tobacco, and cannabis use as well as polydrug use increasing in France?
Addictive Behaviors
(2004)