Exploring the Mediational Role of Coping Motives for Marijuana Use in Terms of the Relation between Anxiety Sensitivity and Marijuana Dependence

Abstract

The current study evaluated the prediction that coping motives for marijuana use would mediate the relation between anxiety sensitivity and a marijuana dependence diagnosis after controlling for other co-occurring marijuana use motives. Participants were 136 current marijuana users (47.1% women; M_age = 21.9, SD = 7.2). Results were consistent with a mediational effect, with the relation between anxiety sensitivity and marijuana dependence being explained by the addition of coping motives into the model. These results provide novel information related to the putative explanatory role of coping motives for marijuana use in the relation between anxiety sensitivity and marijuana dependence.

Marijuana is the most commonly used and abused illicit substance in the United States (U.S.) and many other parts of the world.^1–3 As one illustrative example, approximately 25 million people (8.6%) in the U.S. have reported the use of marijuana within the past year.⁴ Moreover, recent research has indicated that current rates of marijuana dependence are increasing, particularly among young adults in the U.S.⁵

Numerous studies have found that individuals (adults and adolescents) meeting criteria for marijuana abuse or dependence generally have significantly higher rates of psychological symptoms and disorders relative to those not abusing or dependent on marijuana.^6–10 One line of inquiry in regard to the study of marijuana use problems and psychopathology has focused on the relation between anxiety and the frequency of marijuana use. This work suggests that anxiety symptoms and their disorders commonly co-occur with more frequent (e.g., daily) and problematic marijuana use (e.g., marijuana dependence^6,11). Empirical work has documented relatively consistent relations between frequent or severe marijuana use (e.g., marijuana dependence), and panic psychopathology.^12–15 For instance, Hathaway¹⁶ found that approximately 40% of weekly marijuana users reported having had experienced panic attacks related to such use. Other studies have found marijuana dependence to be related to an increased risk of panic psychopathology.^17,18

Anxiety Sensitivity (AS) is one construct that has been showing empirical promise in terms of better understanding certain aspects of marijuana use and its disorders. Anxiety Sensitivity, defined as the fear of anxiety and aversive internal sensations,^19,20 has been conceptualized as a relatively stable, but malleable, cognitive predisposition that arises from genetic and social learning factors.²¹ Theoretically and empirically, AS is unique from, and demonstrates incremental validity relative to, trait anxiety²² and neuroticism;²³ thus, this construct is distinguishable from the frequency of anxiety symptoms and neuroticism.²⁰ Extant work on AS and marijuana has found: (1) current (past 30 day) marijuana users who are high compared to low in AS report greater levels of negative emotional symptoms;²⁴ (2) AS is related to coping-oriented motives for marijuana use (i.e. mechanism for escaping or avoiding distressing anxiety) among current (weekly) users;^25,26 and (3) AS is significantly related to the severity of retrospectively reported marijuana withdrawal symptoms after covarying for frequency of past 30-day marijuana use, concurrent use of other substances as well as anxiety and depressive symptoms among weekly users.²⁷

An emerging theoretical perspective is that high AS marijuana users may be more apt use the drug to cope with aversive anxiety and related symptoms, than individuals low in AS. For example, exposure to life stressors that elicit negative affect among high, as compared to low, AS individuals may elicit greater intensity of negative emotional reactions, such as anxiety symptoms. Under such conditions of heightened emotional distress, the high AS marijuana using person may be more apt to be motivated to engage in marijuana use because he/she believes it will help reduce or manage such symptoms (regardless of objective mood-dampening effects). Such responding is therefore likely to motivate well-learned, reflexive use to reduce (escape) or avoid such acute affect-relevant stressors.

There is limited study of AS in terms of marijuana dependence. (According to the DSM-IV, marijuana dependence reflects a pattern of marijuana use that results in significant and unpleasant consequences; for instance, multiple legal problems, repeated use in physically hazardous situations, and recurrent social and interpersonal problems related to such use. This pattern needs to have occurred within a 12-month period. In addition to these criteria, marijuana dependence indicates compulsive use or tolerance to the drug.²⁸) It is possible that higher levels of AS may be related to a greater likelihood of experiencing marijuana dependence for three non-mutually exclusive reasons. First, as described above, high AS individuals may be more apt to use marijuana regularly to cope with life stressors or in an effort to alleviate negative moods states; thus, leading to more frequent or problematic use of the drug.²⁹ Second, as high AS individuals are more motivated to use marijuana on a regular basis, they may be prone to greater rates of use.²⁵ Such higher rates of use of marijuana are related to a greater tendency to develop tolerance to the drug.³⁰ Third, marijuana discontinuation among active users produces an internally consistent withdrawal pattern (e.g., disrupted sleep, nightmares, nausea, anxiety^31–33 and AS has been shown to be significantly related to self-reported marijuana withdrawal symptom severity.²⁷ Thus, high AS individuals may be more emotionally reactive to marijuana withdrawal symptoms, thereby, increasing the likelihood of continued use to avoid aversive withdrawal symptoms.

The overarching aim of the current investigation was to explore whether high AS individuals are more prone to meet criteria for marijuana dependence, relative to marijuana use, due to increased reliance on the drug in order to cope with aversive interceptive sensations. Specifically, the current study tested the hypothesis that, among individuals currently actively using marijuana, AS would be significantly and incrementally related to a marijuana dependence diagnosis. Additionally, it was hypothesized that coping motives for marijuana use would mediate (explain) the relation between AS and a marijuana dependence diagnosis, even after controlling for other co-occurring marijuana use motives.

Method

Participants

The sample consisted of 136 young adults who reported current marijuana use (i.e., use within the past 30 days), from the greater Burlington, VT community (47.1% women; M_age = 21.9, SD = 7.2). The racial distribution of the sample was consistent with the local population of Vermont with 95.6% of the total sample identifying as Caucasian.³⁴ Approximately 66.6% of the sample reported smoking marijuana at least once per week, with 25.4% reporting use more than once per day. The mean age of onset of regular marijuana use was 15.72 (SD = 5.02) years. Approximately 40.6% of the sample met DSM-IV criteria for marijuana dependence. About 59.2% of the sample reported smoking cigarettes daily, averaging 9.64 (SD = 6.79) cigarettes per day. Approximately 86.6% of the sample reported drinking alcohol at least two to four times a month, with a mean Alcohol Use Disorders Identification Test (AUDIT³⁵) score of 12.12 (SD = 6.01) indicating at least moderate alcohol problems. Participants were excluded if they (a) showed limited mental competency, (b) were not able to give informed written consent, (c) were currently suicidal, (d) met current criteria (past 12 months) for an Axis I mood/anxiety disorder or lifetime history of psychosis, or (e) met current criteria for marijuana abuse.

Measures

Structured Clinical Interview-Non-Patient Version for DSM-IV (SCID-NP³⁶)

Current (past month) marijuana abuse and dependence (with the inclusion of substance withdrawal criteria as defined by the DSM-IV for other drugs and as assessed by the SCID-NP for other drug classes), Axis I mood/anxiety psychopathology, suicidality, and lifetime psychosis were determined using the SCID-NP. Individuals meeting criteria for marijuana abuse were excluded from the current analyses. Individuals meeting criteria for marijuana dependence were coded as “1,” while individuals with no marijuana use disorder diagnosis (marijuana users) were coded as “0.” Individuals meeting criteria for marijuana abuse were excluded from the study, as the investigation focused on a mediational model of AS and marijuana dependence; and studies indicating questionable support for a marijuana abuse distinction.³⁷

Marijuana Smoking History Questionnaire (MSHQ³⁸)

The MSHQ is a self-report instrument that assesses marijuana smoking rate (lifetime and past 30 days), age of onset at initiation, years of being a regular marijuana smoker, and other descriptive information.

Smoking History Questionnaire (SHQ³⁹)

The SHQ is a self-report questionnaire used to assess smoking history and pattern. The SHQ includes items pertaining to smoking rate, age of onset of smoking initiation, and years of being a daily smoker.

Alcohol Use Disorders Identification Test (AUDIT³⁵)

The AUDIT is a 10-item self-report screening measure developed by the World Health Organization that indexes quantity/frequency of alcohol use and alcohol problems.⁴⁰ In the present study, the frequency and quantity items from the AUDIT were used to index current alcohol consumption (an average frequency-by-quantity composite score⁴¹). Additionally, the AUDIT total score was utilized to identify current problems with alcohol use.

Anxiety Sensitivity Index (ASI⁴²)

The ASI is a 16-item measure on which respondents indicate, on a 5-point Likert-type scale (0 = “very little” to 4 = “very much”), the degree to which they are concerned about possible negative consequences of anxiety symptoms (e.g. “It scares me when I feel shaky”). In the present investigation, we utilized the total ASI score, representing the global AS factor.

Marijuana Motives Measure (MMM⁴³)

The MMM is a 25-item measure in which respondents indicate on a 5-point Likert-type scale (1 = “almost never/never” to 5 = “almost always/always”) the degree to which they have smoked marijuana for a variety of possible reasons (e.g. “to be sociable”). Factor analysis of the scale indicates that it has five first-order factors entitled Enhancement (e.g. “because it’s exciting”), Conformity (e.g. “to fit in with the group I like”), Expansion (e.g. “to expand my awareness”), Coping (e.g. “to forget my worries”), and Social (e.g. “because it makes social gatherings more fun” ⁴³).

Procedure

Participants were recruited from the Burlington, VT community for involvement in a study on emotion via placement of study flyers throughout various community settings and posting of printed advertisements in local newspapers. Interested participants who contacted the research team about the study were given a detailed description of the investigation via telephone and scheduled for a laboratory visit. Upon arrival, participants completed a written informed consent, which explained study protocol and procedures. [Note: participants were deemed mentally competent if they demonstrated a comprehensive understanding of the material presented in the consent form as assessed by the ability to provide written consent]. Additionally, participants were administered the SCID-N/P³⁶ by trained interviewers to assess for current Axis I psychopathology in line with the inclusion/exclusion criteria. If eligible, participants then completed a battery of self-report measures. At the completion of the study, participants were debriefed and compensated $25 for their time and effort.

Results

Descriptive Statistics and Zero-Order Correlations

Please see Table 1 for zero-order (or point-biserial, as applicable) correlations for the variables studied. Zero-order correlations reflect the relationship between two variables while ignoring the influence of other variables. Coping motives were significantly positively correlated with the other marijuana use motives (r’s = .14 – .37, p’s < .05). AS was significantly positively correlated with coping motives (r = .37, p < .001), as well as the other marijuana use motives (r’s = .14 – .32, p’s < .05), with the exception of enhancement motives (p > .05). Importantly, AS and coping motives shared only 17% of variance with another, underscoring that they are not overlapping constructs. Both AS and coping motives were significantly positively related to a diagnosis of marijuana dependence (r = .18, p < .05; r = .36, p < .001, respectively).

Table 1.

Zero-Order Correlations among Theoretically-Relevant Variables

Variable	1	2	3	4	5	6	7	Mean or % (SD)	Observed Range
1. ASI	1	.17	.25*	.34**	.27*	.42**	.17	16.33 (8.58)	0 – 48.0
2. Enhancement		1	.51**	−.07	.42**	.42**	.33**	3.78 (0.95)	1.0 – 5.0
3. Social			1	.38**	.49**	.40**	.32**	2.5 (0.99)	0.2 – 4.6
4. Conformity				1	.24*	.17	.17	1.38 (0.57)	0.4 – 4.0
5. Expansion					1	.42**	.27*	2.23 (1.16)	0 – 5.0
6. Coping						1	.43**	2.11 (1.03)	1.0 – 5.0
7. MJ Dependence							1	40.6% Diagnosed	---

Note:

^*p < .01;

^**p < .001;

ASI = Anxiety Sensitivity Index total (Reiss et al., 1986); Enhancement = Marijuana Motives Measure – Enhancement subscale; Social = Marijuana Motives Measure – Social subscale; Conformity = Marijuana Motives Measure – Conformity subscale; Expansion = Marijuana Motives Measure – Expansion subscale; Coping = Marijuana Motives Measure – Coping subscale (Simons et al., 1998); MJ Dependence = Dummy Coded (0 = No, 1 = Yes)

Coping Motives Mediating Anxiety Sensitivity and Marijuana Dependence Relations

The meditational role of marijuana use coping motives in the relation between AS and marijuana dependence was determined using Baron and Kenny’s⁴⁴ test of mediation. Specifically, the test requires the following series of multiple regressions: (1) the predictor variable (i.e., AS) must significantly predict the criterion variable (i.e., marijuana dependence); (2) the predictor variable must significantly predict the mediator (i.e., coping motives); and (3) when the predictor and mediator are entered simultaneously into a third multiple regression, the mediator must significantly predict the outcome, and the relation between the predictor and outcome is either diminished (partial mediation) or non-existent (full mediation). For the present analyses, marijuana dependence was coded as a dichotomous variable (yes/no) based on whether participants met DSM-IV criteria for a dependence diagnosis (please see measure section above).

First, a logistic regression was conducted with AS predicting marijuana dependence. Here, greater levels of AS were significantly related to a positive diagnosis of marijuana dependence (OR = 1.04, 95% CI = 1.00 – 1.08, p = .05). Second, a linear regression was conducted to determine the relation between AS and marijuana use coping motives. Here, enhancement, conformity, expansion, and social marijuana use motives were entered into step 1 of the regression as covariates, and AS was entered at step 2. Step 1 of the model accounted for a significant 26.2% of variance in coping motives (p < .001), with enhancement (t = 2.74, β = .26, p < .01) and expansion motives (t = 2.72, β = .24, p < .01) being significant predictors. Step 2 of the model revealed that increased AS was significantly related to increased motivation to use marijuana for coping motives, above and beyond the variance accounted for in step 1 (t = 4.26, β = .33, p < .001), adding an additional 9.0% of explained variance in coping motives.

Third, a logistic regression was conducted to determine both the relation between the mediator (coping motives) and the outcome (marijuana dependence) as well as to determine the mediating role of coping motives in the relation between AS and marijuana dependence. Here, enhancement, conformity, expansion, and social motives for marijuana use were entered into step 1 of the regression as covariates, and AS and coping motives were entered at step 2. Step 1 of the model predicted 21.8% of variance in marijuana dependence, with enhancement motives being the only significant predictor at that step (OR = 2.18, 95% CI = 1.21 – 3.92, p < .01). Step 2 of the model predicted an additional 9.2% of variance in marijuana dependence and revealed two significant findings. First, coping motives (the mediator) were significantly related to marijuana dependence even after taking AS into account (OR = 2.17, 95% CI = 1.35 – 3.49, p < .01). Second, the relation between AS and marijuana dependence became non-significant with the inclusion of coping motives for marijuana use in the model (p > .05), suggesting that coping motives for marijuana use fully mediated the relation between AS and marijuana dependence. (To ensure that the current findings were unique to coping motives for marijuana use, a supplementary test of specificity also was conducted, replacing coping motives with social motives. Social motives for marijuana use did not significantly mediate AS and marijuana dependence. Please contact Dr. Zvolensky for the full results of this additional analysis.)

One method of strengthening the interpretation of meditational analyses conducted with cross-sectional data is to conduct an additional analysis reversing the proposed mediator and criterion variable.^45–47 Here, we evaluated whether marijuana dependence mediated the relation between AS and marijuana use coping motives. Results were not consistent with mediation in this direction as AS remained a significant predictor of marijuana use coping motives after controlling for both marijuana dependence and the other marijuana use motives (t = 4.27, β = .32, p < .001).

Discussion

Studies have focused on the relation between AS and various aspects of marijuana use.^25–27 There is limited study of AS, however, in terms of understanding marijuana dependence. The current study tested whether high AS individuals are more apt to meet criteria for current marijuana dependence, relative to marijuana use, due to increased reliance on the drug in order to cope with aversive interceptive sensations.

Results indicated that AS was significantly and uniquely associated with a positive diagnosis of marijuana dependence. Additionally, marijuana use coping motives were found to mediate the relation between AS and marijuana dependence. Although the cross-sectional nature of the research design does not allow us to definitively disentangle whether coping-oriented marijuana use occurs after increases in AS symptoms per se,⁴⁴ the present data are consistent with a coping-derived mediational model. Confidence in this model is strengthened by evaluating an alternative explanatory model where marijuana dependence mediated the relation between AS and coping motives. No support was obtained for such a model. Together, the present data suggest that the AS-marijuana dependence association may, at least in part, be accounted for by a motivation to use marijuana for coping reasons. The identification of coping motives as a key mediational element in this relation serves as a potentially clinically important step in the elucidation of the pathways through which high AS individuals are more prone to develop marijuana use disorders. For instance, high AS individuals may be more apt use the drug to cope with anxiety and related aversive symptoms, thereby conferring risk for more frequent and problematic marijuana use.

There are a number of interpretative caveats for the present investigation. First, the present study utilized a cross-sectional design. As such, the current study findings cannot shed light on processes over time or isolate causal relations between variables. Thus, the study results are best construed as a “snapshot” of the relations between AS, coping motives for marijuana, and marijuana dependence. Based upon these data, future, prospective work is needed to evaluate the present model over time. Second, the present sample was comprised of a relatively homogenous group of young adult marijuana smokers who volunteered to participate in the study for monetary reward. We therefore cannot rule out the possibility that the results may be somehow related to a self-selection bias of the present sample. Third, as previously noted, current Axis I psychopathology was excluded from the present investigation; however, we allowed for concurrent use of other substances (e.g. tobacco, alcohol). It is noteworthy that substance use behavior often co-occurs at high rates. For example, the International Consortium of Psychiatric Epidemiology reported that marijuana and alcohol were the two most commonly used substances across six international sites and were frequently co-occurring with one another.⁴⁸ The high rates of marijuana and alcohol use problems in the present sample may be especially elevated due to a sizeable percentage of the participants being in their early twenties, a developmental time frame often characterized by high rates of substance use.³⁹ Fourth, given that self-report measures were employed as the assessment methodology, method variance may have contributed to the observed results. Future work may benefit by using a multimethod assessment approach that can tap automatic aspects of coping responses for marijuana use (e.g., Dot Probe tasks). Finally, the current study is limited in the sense that we did not provide urinanalysis for marijuana use. Future work would therefore benefit by including a urinanalysis assessment to further corroborate marijuana use.

Together, the present investigation represents an important initial step in terms of better understanding the role of AS in terms of marijuana use and its disorders. The results suggest that there may be segments of the marijuana using population who are at relatively greater risk for marijuana dependence by virtue of being motivated to use the drug for coping-oriented reasons. Although still in its infancy, such data highlight potential points of intervention for frequent and potentially problematic marijuana use. Specifically, building from such work, it is possible that coping-based motives for marijuana use also may need to be addressed as part of clinical care for active users with anxiety-related difficulties, who are attempting to quit using marijuana. Indeed, without addressing marijuana use as a coping mechanism, interventions may not be maximizing behavior change efforts.