Abstract

Introduction

Many people view cannabis (or marijuana) as a benign substance with relatively minor negative consequences that should be tolerated for medicinal and recreational purposes (e.g., Zimmer & Morgan, 1997). Permissive beliefs about cannabis are likely fueled by the harmless and even comical manner in which the drug is portrayed in venues of popular culture. However, others argue that there are, in fact, a number of adverse consequences related to cannabis use that could potentially create a significant public health problem should its use increase (Hall & Babor, 2000). The scientific community has not given the study of cannabis the attention it deserves given the popularity of its use, and a more cautious approach to understanding the causes and effects of cannabis use is needed (Hall & Babor, 2000).

Cannabis is the most widely used illicit substance in the United States (Substance Abuse & Mental Health Services Administration, 2003). Its use is increasing among college students, in most student subgroups, and across students enrolled in all types of colleges (Gledhill-Hoyt, Lee, Strote, & Wechsler, 2000). This escalation in use appears to be related to a heightened use of cannabis among younger adolescents as well as increased experimentation and movement toward regular use of the drug after age 18 (Gledhill-Hoyt et al. 2000). More than 50% of adolescents residing in the United States experiment with cannabis and, of those who try the drug more than once, a third eventually escalate to regular use (Gruber & Pope, 2002). For heavier users, symptoms of withdrawal can develop, making it increasingly difficult to quit (Budney, Novy, & Hughes, 1999; Budney, Moore, Vandrey, & Hughes, 2003). Moreover, cannabis use is associated with a number of social, emotional, health, and legal consequences (Degenhardt & Hall, 2006; Dennis et al., 2002; Gruber & Pope, 2002; Hubbard, Franco, & Onaivi, 1999; Khalsa, Genser, Francis, & Martin, 2002; McArdle, 2006; Office of National Drug Control Policy, 2004) and may even serve as a “gateway” to using and abusing other illicit drugs (Fergusson & Horwood, 2000; Fergusson, Horwood, & Swain-Campbell, 2002; Kandel, 2003; Lynskey, Heath, Bucholz, Slutske, Madden, Nelson, Statham, & Martin, 2003).

These findings suggest that prevention and intervention efforts are necessary and must be directed at both college-aged and secondary school-aged students in order to be most effective (Dennis et al., 2002; Gledhill-Hoyt, et al. 2000). However, prevention and intervention cannot be optimally employed until the factors that lead individuals to experiment with and continue to use cannabis are better understood.

Purpose of the Review

It has been substantiated that individuals turn to substances for recreational and social reasons, to enhance and maintain positive internal states, to cope with stress, and/or to reduce or avoid aversive internal states (Goeders, 2004; Johnston & O’Malley, 1986; Sinha, 2005). However, not all drug users report using a given substance for all of the same reasons, and reasons for and expectancies of use vary according to drug type and extent or pattern of use (Boys, Marsden, Griffiths, Fountain, Stillwell, & Strang, 1999; Johnston & O’Malley, 1986; Schafer & Brown, 1991; Simons, Correia, Carey, & Borsari, 1998; Simons, Correia, & Carey, 2000). While there are many risk factors associated with cannabis consumption (van den Bree & Pickworth, 2005; von Sydow, Lieb, Pfister, Hofler, & Wittchen, 2002), and many motives for use (Simons et al. 1998, 2000), we specifically focus on stress for two reasons: first, the body’s stress arousal system is directly affected by cannabis ingestion, and 2) it has consistently been cited as important both in maintaining cannabis use but also as a reason for chronic use.

Stress has been conceptualized as a relationship between an individual and his or her environment that is appraised as exceeding the individual’s coping resources and has the potential to endanger the person’s well-being (Lazarus & Folkman, 1984). The relationship between stress and substance use is well established (Goeders, 2003; 2004; Sinha, 2001; 2005; Turner & Lloyd, 2003; Wills, 1990). However, a comprehensive synthesis and evaluation of studies examining the specific association between stress and cannabis use is lacking. Thus, we conducted a literature review examining the extent to which individuals seek cannabis for stress-coping or tension-reduction purposes. We examined the extent to which family dysfunction, stressful life events (including traumatic stress), and maladaptive methods of coping with stress are related to cannabis use and misuse. Furthermore, we examined whether stress related cannabis use is most prominent in regular and chronic users or in all categories of cannabis users. Finally, we looked at how stress and chronic cannabis use may lead to decision-making deficits that can exacerbate stress and how stress-related alterations associated with cannabis abuse can sensitize individuals to the effects of stress and stress-related cannabis use.

Method

Studies included in this review were drawn from comprehensive MEDLINE (1950–2007) and PsycINFO (1967 – 2007) searches using various combinations of the following keywords: cannabis, marijuana, motives, stress, life events, coping, emotion regulation, trauma, traumatic stress, HPA, and decision-making. A manual search was also performed by scanning reference lists of reviewed articles in order to identify relevant articles that were not selected in our computerized search. The criteria for inclusion in the review were: (a) publication in English and (b) a focus on stress-related factors associated with cannabis use or misuse (e.g., negative family life events, traumatic stress, coping).

Importantly, we focused on the construct of psychological stress and not stress-related psychiatric disorders. The only exception was Posttraumatic Stress Disorder (PTSD) which requires traumatic stress exposure as a diagnostic criterion. Furthermore, while pain associated with medical problems can be stressful, we did not review studies that examined the use of cannabis for pain management (medically supervised or otherwise). Finally, dissertation research was excluded from the review. Due to the breadth of research on this topic, studies with more sophisticated designs and which have more focused goals and informative findings are described in greater detail.

Coping Motives and Cannabis Consumption

According to stress-coping models of addiction, substances are commonly used to cope with life stress by functioning to reduce negative affect and/or increase positive affect (Wills & Hirky, 1996). The model predicts that substance use is most likely when life stress is high and when adaptive coping resources are impoverished (Wills, 1990). Support for this model derives from a wealth of research indicating a robust relationship between stress and substance use (Goeders, 2003; Goeders, 2004; Sinha, 2001; Wills, 1990).

For cannabis users in particular, stress has been cited as a significant factor for its use. Hendlin and Haas (1985) described a series of studies of adolescents and adults who were heavy long-term cannabis users. Their findings, derived from a series of intensive interviews, indicated that cannabis served a number of purposes for adolescents, one of which was to help modify disturbing emotions, particularly intense anger directed toward their parents. For adults, it provided an escape or relief from problems and helped ease the anger and frustration caused by unhappy relationships. Additional support for the model was provided by Crutchfield and Gove (1984) who analyzed data from a national probability sample of adults and found that 15% of cannabis smokers reported using to cope when upset or having personal problems. Consistent with this study, Lee, Neighbors, and Woods (2007) found that 18% of recent high school graduates who used cannabis reported using for stress-coping purposes. On the other, hand higher rates of cannabis consumption for stress-coping purposes have also been reported.

Segal, Cromer, Hobfoll, and Wasserman (1982) examined self-reported reasons for drug use among a sample of detained and adjudicated juveniles. All respondents reported cannabis use, and 51% of the sample reported using more than once per day. Their findings indicated that over 50% of the sample reported using cannabis to “make them feel mellow,” and that this reason was given much less frequently for any other drug category (stimulants, hallucinogens, depressants, & narcotics), suggesting greater use of cannabis for tension reduction as compared with other drugs. Other researchers investigated the characteristics and patterns of cannabis use in adults who had used cannabis regularly for 10 or more years and found that the most common reason for cannabis use (reported by 61%) was to relax and relieve tension (Reilly, Didcott, Swift, & Hall, 1998). Through large surveys of American high school seniors participating in the “Monitoring the Future” study, Johnston and O’Malley (1986) examined reasons for cannabis use according to participants’ degree of involvement with the drug. Participants were categorized into experimental users if they used 1–2 times in their lifetime, occasional users if they used 3–9 times, heavier users if they used 10 or more times, and daily users (a subset of the category of heavier users) if they used on 20 or more occasions in the past 30 days. The investigators found that 72% of daily cannabis users (the most severe group) reported smoking to relax or relieve tension, 36% to escape from problems, 29% to alleviate anger or frustration, and 28% to get through the day. These percentages changed as other groups were examined with 7% of experimental users, 19% of occasional users, and 53% of heavier users using to relax or relieve tension, 3% of experimental users, 11% of occasional users, and 26% of heavier users using to get away from problems, 1% of experimental users, 2% of occasional users, and 11% of heavier users using to get through the day, and 1% of experimental users, 6% of occasional users, and 18% of heavier users using to alleviate anger or frustration. These findings suggested that smoking cannabis for coping-related reasons is reported more frequently by heavier users than by experimental or occasional users, suggesting that coping motives may be more prominent in chronic use of the drug. More recently, Boys, Marsden, and Strang (2001) examined the profiles of young poly-substance users (between ages 16–22; 96.2% lifetime cannabis users) and found that 97% of cannabis users reported using in the past year to help them relax, 69% to feel better when down or depressed, and 58% to help them stop worrying about a problem. Hathaway (2003) presented experienced, mostly long-term and frequent cannabis users aged 18 to 55 with a list of 20 possible reasons for using cannabis and asked them to rate the importance of each. The author found that cannabis use as a coping mechanism was among the most important reasons for use with relaxation being the top reason and over half of the sample reporting other coping motives (to forget your worries; to blow off steam; to see the world with fresh eyes; to feel less anxious) as at least “important” for their use. Green, Kavanagh, and Young (2003) reviewed the literature examining self-reports of cannabis effects that may be associated with ongoing cannabis use and found that, while there was much variation in cannabis effects, relaxation was the most frequently reported effect and reason for use. Finally, Green, Kavanagh, and Young (2004) used a two-group longitudinal design to examine reasons for cannabis use in adult men with and without psychosis. Their findings indicated that, at baseline and follow-up, those with psychosis most commonly reported using cannabis to positively alter their mood (36% and 42%), to help cope with negative affect (27% and 29%), and for social activity reasons (38% and 29%). Those without psychosis most commonly reported using cannabis to relax (34% and 43%), and for social activity reasons (49% and 51%).

Overall, these studies provide evidence that using cannabis to cope with stress or relieve tension is common and may be most prominent in heavier users of the drug. Furthermore, there is some evidence that compared with other illicit drugs cannabis may be most commonly used for stress reduction. Using cannabis for coping purposes may be more prominent in chronic cannabis users possibly because they are unable to use alternative coping or never had the skills for adaptive coping. It is also possible that stress systems are affected by chronic drug use making stress-related motivation to use more salient for chronic users.

A number of studies provide additional support for a role of stress in cannabis consumption by demonstrating an association between coping-motives and cannabis use and/or use-related problems. For example, Boys et al. (1999) interviewed young substance users (aged 16–21) on their perceptions of the function of substance use and perceived likelihood of using substances in the future. They found that perceived mood alteration (to help relax, to feel better when low or depressed, to make activities less boring) was associated with past 90 day frequency and intensity of cannabis use and intent to use cannabis in the future. McKay, Murphy, McGuire, Rivinus, and Maisto (1992) investigated reasons for substance use in a sample of incarcerated adolescents and found that “negative reasons” (when experiencing unpleasant emotions, physical discomfort, and conflict with others) were correlated with their frequency of cannabis use. Chabrol, Massot, and Mullet (2004) examined how drug-related beliefs are related to cannabis use and dependence in a sample of high school students. Using a dependence/non-dependence variable as the criterion, the authors found that relief-oriented beliefs (e.g., “Cannabis helps one to relax and calms anxiety; Cannabis use is the only way to reduce suffering.”) was the only significant predictor of cannabis dependence among users. Anticipatory beliefs (e.g., “To have a nice time, one can take cannabis.”) and permissive beliefs (e.g., “Cannabis is less serious than taking hard drugs.”) did not predict cannabis dependence. However, all three factors were significant in the model that predicted cannabis use, with permissive beliefs being the dominant factor. In an undergraduate sample, Simons et al. (1998) found that coping motives directly predicted cannabis use but not problems, with the relationship being stronger for women than it was for men, and coping motives were associated with cannabis use problems but indirectly through use. In a later study using undergraduates, Simons and colleagues found that coping motives were directly associated with both cannabis use and cannabis use problems (Simons, Gaher, Correia, Hansen, & Christopher, 2005). Lee, Neighbors and Woods (2007) found that coping motives were associated with greater cannabis use-related problems in recent high school graduates. Finally, Bonn-Miller, Zvolensky, and Bernstein (2007) found that coping motives were associated with the frequency of past 30-day cannabis use in young adult cannabis smokers even after controlling for number of years of cannabis use and current levels of alcohol and nicotine use. Furthermore, these authors found that anxiety sensitivity was related to coping motives for cannabis use, but not to other motives.

There is also some evidence that coping motives may be more prominent when examining continuing cannabis use as compared with initial use of the drug. For example, Copeland, Swift, and Rees (2001) investigated the clinical characteristics of adults seeking treatment for cannabis use disorders and found that the most commonly reported reasons for initial use were curiosity, availability, and peer pressure. High rates of co-morbid psychological distress were found in their sample, and stress relief was the most commonly reported benefit and reason for continuing cannabis use.

Overall, this body of literature provides evidence that cannabis users, and especially more chronic users, report that they commonly and consciously seek out the drug for stress-relief and that coping motives are related to cannabis use and use-related problems. The greater coping-related use seen in heavier users may be related to a greater expectancy of positive drug effects (Schafer & Brown, 1991), less pre-morbid ability to cope with stress, or alterations in stress and reward systems as a function of chronic use and cannabis dependence. In the following sections, we will examine some of the stress-related factors associated with early onset cannabis use and continuing consumption.

Stress-related Risk Factors Implicated in Cannabis Use and Misuse

Stress, Cannabis Use & Decision Making Ability

Heavy cannabis users show deficits in decision making ability such that they are motivated more by immediate rewards than by adverse consequences and are slow to learn from their mistakes (Bolla, Eldreth, Matochik, & Cadet, 2005; Whitlow, Liguori, Livengood, Hart, Mussat-Whitlow, Lamborn, Laurienti, & Porrino, 2004). They also demonstrate abnormalities in prefrontal brain-regions involved in making decisions (Bolla et al., 2005). While these studies suggest that heavy cannabis use may lead to poor decision making and associated brain dysfunction, it is also possible that poor decision making associated alterations in brain function predate cannabis use and contribute to greater use over time (Bolla et al., 2005; Whitlow et al., 2004).

Support for the former hypothesis was provided by a recent within- subject repeated measures laboratory study (Lane, Cherek, Tcheremissine, Lieving, & Pietras, 2005) where occasional cannabis users (averaging 7.4 uses in the past 30 days) were given placebo cigarettes and three doses of cannabis cigarettes (half of 1.77%, 1.77%, and 3.58%) and tested using a risk-taking measure. Findings indicated that cannabis significantly increased risky responding, with the 3.58% THC dose having an effect greater than placebo. Overall, this study provided evidence that high doses of cannabis may have direct pharmacological effects on risky decision making and that it may influence decision making by altering one’s sensitivity to consequences (Lane et al., 2005). Consequently, poor decision making associated with acute cannabis intoxication may lead to an increased number of adverse life events (e.g., arrest, incarceration) which, in turn, can lead to greater distress and continued cannabis use for stress-relief.

Psychological stress may also negatively affect the quality of decisions people make (Fishbein et al. 2006; Keinan, 1987). One recent study found that the negative effect of stress on substance use (including cannabis) was mediated through alterations in adolescents’ ability to make and execute pro-social decisions (Fishbein et al. 2006). In all, both chronic cannabis use and stress may disrupt decision-making capabilities and place individuals at increased risk for ongoing cannabis use.

Effects of Cannabis on Brain Stress & Reward Systems

Up until now, we have primarily focused on cannabis use as a response to stress. However, it is also important to consider the profound effects that cannabis itself can have on brain stress and reward systems, which may serve to shift the motivation for cannabis use from positive reinforcing aspects of the drug to negative reinforcing effects. Thus with greater drug use, abstinence related symptoms may contribute to a negative affect state and perpetuate stress-related motivation for drug use (Koob & Le Moal, 1997; 2001). Furthermore, chronic drug use has been found to alter stress responses and enhance drug craving and negative emotions during laboratory induction of stress and alcohol/drug cue exposure in addicted individuals compared to controls (Sinha, 2001; Sinha et al., 2003; Fox et al., 2008; Sinha et al. 2008), measures that contribute to relapse factors in other groups of drug abusers including cocaine dependent (Sinha et al., 2006) and alcohol dependent (Adinoff et al., 2005; Junghanns et al., 2005) populations.

There is evidence that cannabis activates the hypothalamic-pituitary-adrenal (HPA) axis (Brown & Dobs, 2002). Brain imaging data has shown alterations in cortico-limbic circuits that are involved in stress and reward regulation in chronic cannabis users (Eldreth et al., 2004), and recent cannabis use has also been shown to decrease activation in the frontal cortex during emotional stress in cocaine dependent individuals (Li et al., 2005). Several studies have shown that cannabis intake activates the CRF-HPA axis both following acute administration of cannabinoid receptor agonists and THC in animals and in humans (D’Souza et al., 2004; Kumar and Chen, 1983; Puder et al., 1982; Martin-Calderon et al., 1998) as well as during withdrawal (de Fonseca, Carrera, Navarro, Koob, & Weiss, 1997). A study by Weidenfeld, Feldman, and Mechoulam, (1994) also showed that chronic cannabis exposure increased dose-dependent secretion of the stress hormones corticosterone and ACTH in rats. Another study indicated that increased Corticotropin-releasing hormone (CRH) mRNA expression in the rat central amydala may provide a possible mechanism for reported increased CFH release during withdrawal (Caberlotto, Rimondini, Hansson, Eriksson, & Heilig, 2004). Acute cannabis administration is also known to increase dopamine transmission in the nucleus accumbens (NAC) and mesolimbic reward systems via its action on central cannabinoid receptors (Cheer et al., 2004; Szabo et al., 1999) as well as increase prefrontal cortical catecholaminergic utilization function in rats (Jentsch et al., 1997). Many preclinical studies have also demonstrated the impact of cannabinoids on central noradrenergic function. Studies using synthetic cannabinoid agonists have shown that SR 141716A increases levels of norepinephrine in both the rat anterior hypothalamus and the frontal cortex (Tzavara et al., 2001; 2003). The cannabinoid receptor agonist WIN 55,212-2 has also been shown to dose-dependently increase the release of norepinephrine in the prefrontal region (Oropeza et al., 2005).

While there is a need to conduct more research in humans to support cannabis use related changes in stress responses, this line of research suggests that, in addition to being a response to stress, chronic cannabis consumption may impact brain development and sensitize individuals to the effects of subsequent life stressors. In effect, a vicious cycle may ensue with stress contributing as a risk factor to increase cannabis use and greater cannabis use altering brain stress and reward systems that enhance stress responses, decrease the capacity to cope with stress, and increase the salience of the drug and drug use behaviors (Sinha, 2001; 2005).

Conclusion

Numerous studies indicate that cannabis is commonly and consciously used as a stress-coping strategy. Stress-related factors including family dysfunction, negative life events, and traumatic stress are all associated with cannabis consumption. It appears that stressful life circumstances, especially those that occur early in life, may elevate distress, increase sensitivity to stress, and set individuals on a trajectory toward experimental cannabis use and a more severe course of addiction. Coping deficits that may develop from deficient care-giving and modeling of deviant peers may compound problems by reducing the coping-arsenal necessary to effectively overcome life stressors and modulate negative affect. In effect, cannabis use may be most likely in stress-vulnerable individuals as it supplies immediate stress-relief with relatively little effort. This is not to say that other factors do not influence cannabis use. Indeed, genetics may converge with psychosocial factors to influence cannabis consumption (Gruber & Pope, Jr., 2002; Lynskey et al., 2002).

While many people may be able to use cannabis socially and without consequence, there may be a subset of individuals who experience greater life stress, are more vulnerable to stress, and who may be more likely to use cannabis for stress-coping purposes. Importantly, these individuals may be at increased risk for earlier and heavier cannabis use and greater cannabis-related problems. This view is supported by a recent study that found that young adults who used cannabis primarily as a coping strategy had poorer mental health, greater pathology, more distress, and more life events than non-users whereas those with predominantly social reasons for use were not more distressed than non-users (Brodbeck, Matter, Page, & Moggi, 2007). Chronic cannabis use may further compound problems by altering brain stress and reward systems, thereby sensitizing individuals to the effects of stress. Together, these findings indicate that stress-coping focused interventions may be best applied if specifically targeted toward this subgroup of stress-vulnerable cannabis users.

A recent review indicated that cannabis dependence appears responsive to cognitive-behavioral, motivational enhancement, and contingency management interventions (McRae, Budney, & Brady, 2003). The literature we reviewed here suggests that enhanced cognitive-behavioral and pharmacological interventions specifically focused on reducing, planning for, tolerating, and coping appropriately with general life stress and traumatic stress may further improve treatment outcomes. Participation in stress-reducing activities outside of therapy, such as exercise and Yoga, may also be beneficial (Michalsen, Grossman, Acil, Langhorst, Ludtke, Esch, Stefano, & Dubos, 2005; Southwick et al., 2005; Tsatsoulis & Fountoulakis, 2006). However, given the varied reasons for cannabis use and misuse, the most effective prevention and interventions programs could benefit from incorporating stress-coping treatments with community and psychosocial interventions that enhance pleasurable activities, alter deviance-prone attitudes, and improve family, school, and social functioning. Harm reduction approaches focused on reducing the amount of cannabis ingested may also temper the stress-response, improve decision making capabilities, and lead to less aversive consequences. Reduced consequences, in turn, may translate to lower distress and less coping-related use of cannabis. Of course, randomized controlled trials are needed before any definitive conclusions or recommendations can be made.

Parents, teachers, and community and religious leaders should become more aware of the stressors children and adolescents face and implement strategies to prevent cannabis use. For instance, while childhood abuse is undoubtedly a stressful experience that necessitates immediate attention, social pressure may be a less obvious, but significant, form of stress to which adolescents must contend. The anxiety manifested in social pressure situations may lead to cannabis use as a stress-reduction strategy as well as a means to gain peer approval (Comeau, Stewart, & Loba, 2001). In all, early detection, intervention, and support for troubled adolescents may prevent experimental cannabis use and/or deter progression to problematic use (e.g., Butters, 2002). However, additional work is needed to understand the stress-related factors associated with the various stages of cannabis use and how to apply the findings to prevention and intervention programs. Further work is also needed to understand how chronic cannabis use influences brain-stress responding in humans.

A limitation of our review is that we specifically focused on stress, negative life events, and maladaptive coping as stress-related factors implicated in cannabis consumption. Viewing the problem from another perspective, positive life events and adaptive forms of coping may be protective. Indeed, positive affect has been associated with lower levels of substance use in prospective studies (Wills et al. 1999), and more research is needed to address how individuals can obtain and enhance pleasant emotions in an effort to prevent drug addiction (Labouvie, 1986).

Acknowledgments

Footnotes

References