BACKGROUND AND OBJECTIVES
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- BACKGROUND AND OBJECTIVES
- DISCUSSION AND CONCLUSIONS
Data from the National Epidemiological Survey on Alcohol and Related Conditions demonstrates that 28% of adults in the US who smoke tobacco concurrently use cannabis. Given that concurrent tobacco–cannabis users believe that they are more physically and mentally addicted to nicotine and are less likely to quit smoking cigarettes than nonusers of cannabis,[3, 4] tobacco cessation interventions for concurrent tobacco–cannabis users may be enhanced by targeting mechanisms underlying cannabis use. Unfortunately, scarce research describes why tobacco users may use cannabis. To date, most research on the underlying mechanisms of cannabis use has neglected cannabis' link to tobacco.
The majority of research into cannabis use motives has relied upon collecting data from mixed samples (ie, some use tobacco while other participants do not) and controlling statistically for concurrent tobacco use. This research has found that stronger endorsement of coping, enhancement, social, and expansion motives is associated with greater frequency of cannabis use. Further, studies have shown that using cannabis to cope is related to an increased risk for negative emotional symptoms and disorders, while using cannabis for enhancement purposes is related to greater positive affectivity and lower anxious arousal.[7, 8] Individual differences in emotional vulnerability may contribute to these observed relations, such that those who are very sensitive to anxiety may be more apt to use cannabis to cope with their negative affect, while those who are less sensitive to anxiety may be more likely to use cannabis to increase their positive affect. Partially consistent with this speculation, positive associations between anxiety sensitivity and coping motives for cannabis use have been reported when controlling statistically for concurrent tobacco use[6, 9]; however, enhancement motives have not been related to anxiety sensitivity.
In order to identify methodological changes that will improve research and further our knowledge about the relationship between concurrent cannabis and tobacco use, we believe it is necessary to examine the limitations of the above-mentioned research. First, and foremost, previous work has relied upon statistically controlling for tobacco use. Although useful for establishing how anxiety sensitivity and motives relate to cannabis use independently of tobacco use, failure to examine these risk factors explicitly among concurrent tobacco–cannabis users has prevented an understanding of why cigarette smokers use cannabis, and therefore has limited researchers' ability to tailor smoking cessation treatment to target concurrent cannabis use, a behavior that contributes to cigarette smoking. Second, most research has focused on the individual effects of these variables in relation to cannabis use, which has not allowed researchers to understand how the combination of these variables influences cannabis use (ie, examination of associations in one overarching model). This issue is clinically important, as cannabis use motives are highly related to one another.[10, 11] Similarly, past work has predominately targeted the main effects of these variables. Such an approach does not take into account how anxiety sensitivity may qualify cannabis use motives effects and may lead to false conclusions that anxiety sensitivity is not related to use motives. As an example, research with tobacco smokers found that while indulgent smoking motives were not related to anxiety sensitivity, the interaction between indulgent smoking motives and anxiety sensitivity significantly predicted cigarette use. Level of cigarette use was related to indulgent motives only for individuals low in anxiety sensitivity. Lastly, previous research has focused on frequency of use. Recent research demonstrates that quantity of cannabis use is a stronger predictor of cannabis problems than frequency of use, and thus, may be a more clinically meaningful variable. Importantly, quantity estimates for cannabis use have been found to be reliable.
The purpose of this paper, therefore, was to address key limitations of past work by evaluating both the main and interactional effects of anxiety sensitivity and cannabis use motives among a treatment-seeking sample of cigarette smokers. We studied a treatment-seeking sample as we were interested in obtaining data relevant to the refinement of tobacco cessation interventions for concurrent cannabis use. In line with past research, we expected coping, enhancement, social, and expansion motives to exhibit positive relationships with quantity of cannabis use when examining zero-order correlations. Further, we hypothesized that anxiety sensitivity would moderate the relationships between enhancement motives and quantity of cannabis use, such that enhancement motives would be associated positively with quantity of cannabis use only for low anxiety sensitive individuals. Conversely, we also hypothesized that anxiety sensitivity would moderate the relationship between coping motives and quantity of cannabis use, such that coping motives would be associated positively with quantity of cannabis use for high anxiety sensitive individuals only. Although our main aim of this paper was to explore these relations for quantity of cannabis use, we conducted an exploratory analysis to discover whether the moderation model would be similar for frequency of cannabis use.
- Top of page
- BACKGROUND AND OBJECTIVES
- DISCUSSION AND CONCLUSIONS
See Table 2 for zero-order correlations among studied variables. As expected, enhancement, social, coping, and expansion motives were correlated positively with quantity of cannabis use per occasion in the previous week. Education, age, and marital status were related to quantity of cannabis used and were included as covariates in the regression analysis. Conformity motives were not included in the model because they were not related statistically to quantity of cannabis use. The interaction between anxiety sensitivity level and coping motives was not statistically significant (p = .99, B = −.0001, SEB = .01), and it was removed from the model (data not displayed in Table 3). Table 3 demonstrates that when all relevant motives and covariates were included in one model, the interaction between anxiety sensitivity and enhancement motives was related marginally to quantity of cannabis use (p = .10). Examination of the simple slopes demonstrated a disordinal interaction (lines that intersect; see Fig. 1). Enhancement motives were not related to cannabis use for individuals high in anxiety sensitivity (Wald χ2 = .06, p = .81, B = .01, SEB = .03), but were related to cannabis use for those low in anxiety sensitivity (Wald χ2 = 11.06, p < .001, B = .05, SEB = .02). When the model was repeated for frequency of use, the interactions between anxiety sensitivity level and coping (p = .74, B = −.003, SEB = .008) and enhancement motives (p = .29, B = −.01, SEB = .01) were not statistically significant (data not displayed in Table 3). Table 3 demonstrates that when the interactions were removed from the model, the main effects for enhancement, coping, and conformity were statistically significant.
Table 2. Zero-order correlations among theoretically relevant variables
|2. Gender|| ||.04||.07||−.07||.19*||−.22*||.03||−.03||.16||−.08||−.003||−.10||.09||−.14s|
|3. Race|| || ||−.05||−.05||−.11||.02||.004||−.05||.10||−.15||−.19*||−.14||.13||−.18*|
|4. Education|| || || ||−.05||−.13||.34***||−.18*||−.18*||−.10||−.12||−.03||−.14||−.15||.02|
|5. Marital status|| || || || ||.01||−.27**||.20*||.20*||.07||.07||−.01||.17*||.03||.01|
|6. Psychiatric disorder|| || || || || ||−.11||.19*||.11||.17||.11||.13||.04||.21*||.12|
|7. Years of cannabis use|| || || || || || ||−.003||−.01||−.03||.03||.02||−.15||−.01||−.10|
|8. Frequency of cannabis use|| || || || || || || ||−.30***||.02||.48***||.20*||−.18*||.41***||.26**|
|9. Quantity of cannabis use|| || || || || || || || ||−.07||.40***||.30**||−.04||.27**||.27**|
|10. ASI-3|| || || || || || || || || ||.09||.13||.14||.31***||.14|
|11. MMM-enhancement|| || || || || || || || || || ||.51***||−.02||.33***||.46***|
|12. MMM-social|| || || || || || || || || || || ||.39***||.52***||.56***|
|13. MMM-conformity|| || || || || || || || || || || || ||.24**||.22*|
|14. MMM-coping|| || || || || || || || || || || || || ||.44***|
|15. MMM-expansion|| || || || || || || || || || || || || || |
Table 3. Negative binomial regression analysis for anxiety sensitivity, motives, and cannabis use
|Model||B||SEB||95% CI||Wald χ2||p-Value|
|Quantity of cannabis use|
|Marital status||.28||.17||−.06, .61||2.58||.11|
|MMM-enhancement by ASI-3||.05||.03||−.009, .10||2.73||.10|
|Frequency of cannabis use|
|Marital status||.25||.12||−.008, .49||4.11||.04|
|Psychiatric disorder||.04||.04||−.04, .12||.84||.36|
Figure 1. The upper graph displays the association between enhancement motives and quantity of cannabis per use occasion by low and high anxiety sensitivity status as determined by Jacobson and Truax's formula for calculating clinical significance, whereas the bottom graph displays the association between enhancement motives and quantity of cannabis per use occasion by low, moderate, and high anxiety sensitivity status as determined by a tertile split.
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When the regression model was repeated using ASI-3 scores as a continuous variable, the interaction between anxiety sensitivity and enhancement motives was not statistically significant (Wald χ2 = 1.95, p = .16, B = −.002, SEB = .001). Likewise, the interaction was not statistically significant when using a median split (Mdn = 13; Wald χ2 = .89, p = .34, B = −.03, SEB = .03); however, the interaction was marginally significant when using a tertile split (tertile 1, 0 to <10; tertile 2, 10 to <21; tertile 3, 21–54; χ2 = 5.41, p = .07). Examination of the simple slopes (Fig. 1) demonstrated that the slope for those in the middle tertile significantly differed from the slope for those in the highest tertile (Wald χ2 = 5.32, p = .02, B = .07, SEB = .03); however, the slope for the middle tertile did not statistically differ from the slope for the lowest tertile (Wald χ2 = 2.28, p = .13, B = .05, SEB = .03). Although individuals in the lowest tertile reported using more cannabis for enhancement motives than those in the highest tertile, the difference between these slopes was not significantly different from each other (ie, the slopes were roughly parallel; Wald χ2 = 1.04, p = .31, B = .03, SEB = .03).
DISCUSSION AND CONCLUSIONS
- Top of page
- BACKGROUND AND OBJECTIVES
- DISCUSSION AND CONCLUSIONS
The purpose of the present study was to examine comprehensively the relations among anxiety sensitivity, cannabis use motives, and quantity of cannabis use in a sample of individuals seeking smoking cessation treatment. Consistent with prediction and past research, reports of stronger coping, enhancement, social, and expansion motives were associated with using greater quantities of cannabis at the univariate level. After adjusting for relevant sociodemographic variables in a model that included all these motives, the relationship between enhancement motives and cannabis use was found to slightly vary as a function of anxiety sensitivity level. Specifically, enhancement motives were related to quantity of cannabis use per occasion, only for individuals categorized as low in anxiety sensitivity. Contrary to expectations, anxiety sensitivity did not moderate the relationship between coping motives and quantity of cannabis use. Unlike the model for quantity of cannabis use, using cannabis more often for enhancement and coping purposes was related to greater frequency of use, while using cannabis for conformity purposes was related to less frequent use. These findings for frequency of use are consistent with previous research that has found using cannabis for a variety of reasons is related to more severe cannabis use.
The differences noted between frequency and quantity of cannabis use may be explained partially by the dose-dependent effects of cannabis. Cannabis use may have bidirectional dose-dependent effects, such that at low doses cannabis produces anxiolytic effects while at higher doses it produces anxiogenic effects. This dose-dependent effect may explain why enhancement and coping motives were not related to greater quantities of cannabis use for high anxiety sensitive individuals. Individuals high in anxiety sensitivity may find smoking large amounts of cannabis to be aversive, but individuals low in anxiety may find these effects enjoyable. Accordingly, anxiety sensitivity may exert influence on how much cannabis someone uses, rather than how often someone uses cannabis. Experimental studies that manipulate dose of cannabis use across individuals high and low in anxiety sensitivity would assist in validating or refuting this hypothesis. Conducting such a study with both cannabis only users and tobacco–cannabis users would demonstrate whether these bidirectional concerns differ as a function of cigarette smoking status.
A number of limitations to the study must be noted. First, the present study utilized a cross-sectional design. Although cross-sectional research is useful for providing an initial test for cannabis use motives and anxiety sensitivity among a clinical sample of cigarette smokers, longitudinal research is needed to establish causal relations. Experience sampling methodology would help to demonstrate causally how motives contribute to use. Further, longitudinal research is needed to understand if and how cannabis use may influence an individual's sensitivity to anxiety. While there is substantial evidence that many individuals smoke cannabis to reduce anxiety, much less research has examined how cannabis use can contribute to anxiety over time. Second, in line with recommendations for examining interaction effects, marginally significant interaction terms were included in the regression model.[37, 38] Obtaining a larger sample would prevent the need to do so in future studies. Lastly, the sample was comprised of treatment-seeking cigarette smokers. While such a sample was the intended focus of the investigation, findings may not generalize to all cigarette smokers. Future research needs to examine if study results can be replicated in cigarette smokers not wishing to cease their use and/or those aiming to reduce on their own.
Despite study limitations, this study had a number of strengths. To the best of our knowledge, this study was the first to explicitly examine motives for cannabis use in individuals who concurrently use tobacco. In addition, this study provided a comprehensive examination of cannabis use motives and their relation to cannabis use. According to motivational theories, one individual may use a particular substance for a variety of reasons, and thus, it is important to examine relations between one motive and cannabis use in the context of other motives for use. Furthermore, this study examined how anxiety sensitivity potentially qualifies cannabis use motives effects. Importantly, our method for categorizing individuals as high or low in anxiety sensitivity based on Jacobson and Truax's definition of clinical significance was supported by obtaining similar results using a tertile split and by the absence of a statistically significant interaction when examining anxiety sensitivity as a continuous variable or dichotomized using a median split. These findings suggest that anxiety sensitivity has differential effects for low and high anxiety sensitive individuals, rather than for low versus moderate-high anxiety sensitive individuals (median split). Furthermore, the effect is simply not a matter of experiencing lesser or greater amounts of anxiety sensitivity, but rather what type (low vs. high). The lack of significant or clinically important interaction when examining anxiety sensitivity as a continuous variable adds support to the growing body of literature that suggests anxiety sensitivity has a categorical latent structure, rather than dimensional.[30, 31] Using Jacobson and Truax's formula to derive anxiety sensitivity categories is a novel, meaningful approach to examining interactions compared to a tertile split cut-off. In addition, mean ASI-3 scores for individuals categorized as low and high were comparable to published means for nonclinical and clinical samples.[31, 46]
Taking into account study strengths and weaknesses, clinical researchers may want to examine the utility of helping clients low in anxiety sensitivity who use both cannabis and tobacco to participate in alternative behaviors that result in experiencing excitement and fun, but that are associated with less health risk than smoking cannabis. As clients may perceive healthier behaviors to be less pleasurable than using cannabis, clinical researchers also may want to focus on teaching clients to accept the trade-off that results from engaging in healthier behavior.