Anxiety disorders and rates of cannabis use are both highly prevalent. The current global prevalence of anxiety disorders is between 5.3% and 10.4%.1 According to Health Canada,2 29% of Canadians ages 16 and older reported using cannabis in the past 12 months. The 12-month prevalence of Cannabis Use Disorder (CUD) is 3.5% for men and 1.7% for women.3 Research has shown a link between cannabis use and anxiety symptoms such that individuals with high levels of anxiety symptoms use cannabis at an elevated rate compared to those with lower levels of anxiety symptoms.4
A systematic review by Crippa et al5 concluded that regular cannabis users are more likely to have an anxiety disorder than nonusers, and those with anxiety disorders are more likely to use cannabis at higher rates than those without an anxiety disorder. Associations between cannabis dependence and anxiety disorders have also been identified.6 A meta-analysis of 31 studies found that anxiety disorders are positively associated with cannabis use and CUD.6 Furthermore, the rate of comorbidity of CUD and any anxiety disorder is 23.4% for males and 36.1% for females.3 These results suggest a positive association between anxiety symptoms and cannabis use.
However, some studies have shown no association between cannabis use and anxiety symptoms. In general population samples, cannabis use has been described as a minor risk factor for increased anxiety or has not been found to be associated with increased risk of anxiety.7,8 Other researchers have claimed that there is a negative association between social anxiety symptoms and cannabis use.9
The association between cannabis use and anxiety symptoms may be explained by the tension-reduction model, which suggests that substances are used to reduce unpleasant emotions (i.e., tension).10 The tension-reduction model has been used to describe the motivation for alcohol use and has been supported within the alcohol abuse literature.11 Drinking alcohol can reduce feelings of tension and therefore, alcohol consumption is negatively reinforced.12 Researchers have begun to study cannabis use within the tension-reduction model.13 In support of this model, research has shown that a common motive for using cannabis is to reduce stress or tension.14–16 Cannabis users have reported that there tends to be increased use of cannabis during times of psychological distress17 and that a common effect of cannabis is a decrease in feelings of tension.16 More recently, researchers have found support for cannabis reducing negative affect.18 A large proportion of the literature examining associations between cannabis use and anxiety symptoms has been conducted using nonclinical community samples. Therefore, further research is needed to examine these associations in a large clinical sample.
Commonly reported motives for cannabis use include enjoyment, conformity, experimentation, social enhancement, boredom, relaxation, and coping.15 Interestingly, individual motives for cannabis use have been associated with the frequency and severity of cannabis use, as well as cannabis use problems.14,15,19 Specifically, using cannabis to cope with negative affect is significantly associated with increased frequency of cannabis dependence symptoms.14 Hyman and Sinha20 found that individuals who use cannabis chronically are more likely to use cannabis to cope with stress compared to those who have only experimented with cannabis. Coping motives for cannabis use are significantly associated with greater amounts of cannabis used.19 However, there is relatively little research looking at rates of cannabis use, the amount and frequency of cannabis use, and rates of CUD in people with clinical anxiety and related disorders. This population by definition has difficulty coping with stress and regulating their emotions.21 Based on the current literature, coping motives may be particularly common in cannabis users who are seeking therapy for anxiety and related disorders and therefore rates of chronic or problematic use may be high.
If individuals with anxiety or related disorders have higher rates of chronic or problematic cannabis use, there are important implications for clinicians working with anxious clients. For example, clinicians might need to be vigilant in screening for problematic cannabis use in this population to determine optimal treatment approaches (e.g., comorbid anxiety/substance use treatment, treat CUD before anxiety). This line of research is especially important given that Canada has recently legalized cannabis use. Legalization may contribute to the normalization of cannabis use as a method to cope with distress, which could further increase rates of use in this population. Due to the inconsistent findings of the relationship between anxiety and cannabis use and the limited amount of studies addressing the prevalence and severity of cannabis use in clinical samples of individuals seeking treatment for anxiety and related disorders treatment, this study intends to address these research gaps.
This study describes patterns of cannabis use in a sample of individuals seeking treatment for anxiety disorders (e.g., panic disorder, agoraphobia, social anxiety disorder, generalized anxiety disorder) and related disorders [e.g., obsessive-compulsive disorder and post-traumatic stress disorder (PTSD)] at a specialized hospital-based outpatient clinic. Specifically, this study characterizes the proportion of patients who report recently using cannabis, the frequency and amount of cannabis used, the proportion of patients who exceed the cutoff score on a measure of cannabis use symptoms which suggests that CUD criteria is likely met, motives for cannabis use, and whether or not cannabis users are more likely to abuse alcohol than cannabis nonusers.
Based on the tension-reduction model, it is hypothesized that individuals presenting to an anxiety clinic will report an elevated rate of cannabis use compared to the general population and that those who endorse more depression and anxiety symptoms will use cannabis more frequently and in larger amounts than those who report fewer symptoms. Consequently, we predict that patients with higher symptoms of psychological distress will be more likely to score higher on a measure of cannabis use symptoms and exceed the threshold associated with CUD. Further, it is hypothesized that the primary motive for cannabis use in this population will center around attempts to regulate mental health symptoms. It is also hypothesized that those who use cannabis at an elevated rate may also use alcohol at an elevated rate to further reduce their distress.
A total of 796 patients (n = 308 cannabis users; n = 488 non-cannabis users) were recruited from a large, specialized anxiety and related disorders clinic in an academic hospital in Ontario, Canada. For the purpose of the present study, patients who endorsed using cannabis at least once in the past 6 months on a screening question were considered cannabis users. Patients were seeking treatment services for an anxiety or related disorder as per their family physician's or other healthcare professionals’ referral. Sample demographics are summarized in Table 1. Note that cannabis users and nonusers differed by age, education, and ethnicity (Table 1).
As part of the intake procedure at the clinic, all patients completed a battery of self-report measures, including the Depression Anxiety Stress Scales 21 (DASS-21)22 and the Alcohol Use Disorder Inventory Test (AUDIT).23 All cannabis users (N = 308) completed the Cannabis Use Disorder Identification Test-Revised (CUDIT-R)24 between May 9, 2018 and February 24, 2019, and 53 cannabis users also completed the Marijuana History Questionnaire (MHQ)25 between January 14, 2019 and February 24, 2019, therefore providing a snap shot of cannabis use near October 17, 2018, the date of legalization of cannabis in Canada. All patients provided written consent to participate in this study. The study was approved by the institutional research ethics board.
The DASS-21 is a 21-item measure of distress with 3 subscales: depression, anxiety, and stress states.22 Items are rated on a 4-point scale, from 0 = Did not apply to me at all to 3 = Applied to me very much or most of the time. Scores are summed and multiplied by 2 for each scale to yield total scale scores. Higher scores indicate increased severity. Cutoff scores have been determined, which indicate normal, mild, moderate, severe, or extremely severe symptoms.22,26
The AUDIT is a 10-item self-report screening tool for symptoms of alcohol use disorder (AUD).23 Each item is scored from 0 to 4 and a total score is achieved by summing the rating on each item. Total scores above 8 suggest problematic alcohol consumption.23
The CUDIT-R is an 8 item self-report screening tool for symptoms of CUD in the past 6 months.24 Items reflect 4 domains: consumption, cannabis problems, dependence, and psychological features. Each item is rated on a 5-point scale, ranging from 0 = Never or Less than 1 to 4 = 4 or more times per week. The CUDIT-R has high sensitivity (91%) and specificity (90%) with the suggested cutoff score of 13, where those who score above 13 are likely to have CUD.24
The MHQ is a 32-item, self-report data collection tool. It measures cannabis use history including information about method of consumption, frequency and amount of use, age of first use, and motives for use.25 Multiple responses can be selected for questions related to reasons for use (i.e., medical, psychiatric) and method of consumption (e.g., smoking, vaping, eating). Given that only a subset of questions from the MHQ addressed the objectives of the present study, some MHQ questions were excluded.
The proportion of patients seeking therapy for anxiety symptoms who reported cannabis use in the past 6 months was calculated by dividing the proportion of users by the total sample size. To describe patterns of cannabis use, the mean age of first use was calculated, frequency analyses were conducted for various rates of use endorsed, and the mean amount of cannabis used in grams per session, day, and week, in the past 3 months was calculated. The proportion of patients who smoke, vape, and ingest cannabis was calculated to describe methods of cannabis consumption within this population. Frequency analyses were used to determine the primary methods of smoking (e.g., joints, bong) and vaping (e.g., vaping pens, other portable devices), and the proportion of people who vape concentrates or marijuana plant material. The severity of cannabis use was reflected by the mean total CUDIT-R score and the proportion of patients who likely met criteria for CUD (i.e., score 13 or higher on the CUDIT-R). Rates of total CUDIT-R scores of 13 or over were compared between individuals identifying as male or female as well as frequency of cannabis use. Note that rates of cannabis use in transgender and intersex individuals were not included due to small sample sizes. In addition, to explore the hypothesis that cannabis users may use to reduce distress, Pearson correlations were conducted between the CUDIT-R and DASS-21 total scores as well as DASS-21 subscale scores. To further examine the motives for cannabis use, the proportion of patients who endorsed using cannabis for medical reasons, using with the authority of a medical doctor, and for various medical and psychiatric purposes, were calculated. Pearson correlations were also conducted between the AUDIT and DASS-21 scores to determine if alcohol may be used to reduce distress in cannabis users and nonusers. A Pearson correlation between total AUDIT and CUDIT-R scores was also calculated in cannabis users, to determine if alcohol and cannabis use severity were associated in this population. An independent samples t test was conducted to determine if there was a significant difference in total AUDIT scores between cannabis users and nonusers. Levene's test for equality of variance was violated, therefore the t test correction for unequal variances is reported below.
Cannabis users were significantly younger than nonusers [t(735.54) = 5.82, P < 0.001]. As indicated in Table 1, education and ethnicity differed significantly between cannabis users and nonusers [χ2(2) = 9.22, P = 0.010; χ2(6) = 15.22, P = 0.019, respectively]. Sex and relationship status did not differ significantly between users and nonusers [χ2(2) = 1.18, P = 1.183; χ2(1) = 1.18, P = 0.030, respectively].
Description of Cannabis Use Patterns
Thirty-nine percent (n = 308) of patients seeking treatment for anxiety reported using cannabis in the past 6 months. The mean age of first use was 17.42 years [standard deviation (SD) = 3.83], the youngest and oldest ages of first use reported being 11 and 30 years old. In the past 6 months, 43% of cannabis users endorsed using 4 or more times per week, 33% using monthly or less, 12% using 2 to 4 times per month, and 9% using 2 to 3 times per week. Three percent reported never using which may be explained by patients who used cannabis in the past 6 months but do not use on a regular basis (e.g., they may have tried it for the first time in the past 6 months or they may use only on special occasions). Frequency of cannabis use was generally similar between males and females, with the largest proportion of patients using 4 or more times a week (41% of females and 46% of males).
More detailed information about patterns of use was collected for a subset of patients (n = 53). In a typical session, patients reported using a mean of 0.31 g of cannabis (SD = 0.42). On a typical day when using cannabis, they reported consuming an average of 0.53 g (SD = 0.82). In a typical week when using cannabis, they reported consuming an average of 2.65 g (SD = 4.82), with a maximum of 21 g. A total of 78 responses were made regarding method of consumption by the 53 patients who completed the MHQ. Note that patients could endorse as many responses about method of consumption as applicable. Twenty-one individuals made a single response for primary mode of use (smoking, vaping, or edibles), 12 individuals made 2 responses, and 11 individuals made 3 responses. Of the 78 responses, 49% endorsed consuming cannabis via smoking, 24% via vaping, and 27% via edibles. Of the 38 patients who endorsed smoking as a primary method of cannabis consumption, 49 responses were made to specify most common smoking methods (e.g., joints, bong). Forty-seven percent of responses were made for smoking joints, 38% smoking via pipes, bowl, or one-hitter, 12% reported using a bong, and only 4% using blunts (marijuana in cigars) and spiffs (tobacco and marijuana in a joint). No respondents endorsed frequently using a hookah. Of the 19 patients who endorsed vaping as one of their primary methods of consumption, 20 responses were made to specify most common vaping methods. Forty-five percent endorsed vaping pens, 40% endorsed other portable devices, 10% endorsed dab/oil rings, and 5% endorsed using tabletop vapes. No reports of e-cigarettes as a common form of consumption were made. Sixty percent of these patients fill their vapes with dried marijuana plant material and 40% fill them with concentrates. Of the 308 cannabis users, the mean CUDIT-R score was 8.38 (SD = 6.97). Twenty-two percent scored a total of 13 or above on the CUDIT-R, and were therefore likely to meet criteria for CUD. Thirty-two percent of males and 11% of females scored 13 or above on the CUDIT-R.
Correlates of Cannabis Use and Reasons for Use
There was a positive and significant correlation between the total DASS-21 and CUDIT-R scores (r = 0.29, P < 0.001) representing a small to medium effect size. Similar correlations were found between the CUDIT-R and each of the DASS-21 subscales (stress: r = 0.22, P < 0.001; anxiety: r = 0.23, P = 0.010; depression: r = 0.30, P < 0.001). Of the 53 patients who completed the MHQ, 45% of users reported using cannabis for medicinal purposes but only 17% of patients reported that their cannabis was prescribed by a medical doctor (23% reported that it was not prescribed and 60% did not provide an answer). Given that patients could endorse multiple responses to best represent their motives for use, 86 responses were made to represent the most common medicinal reasons for cannabis use, suggesting that some patients endorsed multiple reasons. In terms of medical reason or psychiatric reasons for cannabis use, 4 individuals endorsed 1 answer, and 19 individuals gave 2 or more reasons. Twenty-one percent (n = 18) of responses suggested that cannabis was used to aid sleep, 21% (n = 18) to simulate appetite, manage nausea or vomiting, 20% (n = 17) to manage pain, 19% (n = 16) to manage psychiatric disorder (anxiety, depression, schizophrenia, etc.), 6% (n = 5) for inflammation, 6% (n = 5) for fibromyalgia, 5% (n = 4) for arthritis, 2% (n = 2) for gastrointestinal disorders, and 1% (n = 1) for other reasons. Thirty-eight responses provided more specific psychiatric reasons for cannabis use. Three individuals made 1 response and 13 individuals made more than 1 response. Thirty-nine percent (n = 15) of responses suggested that use was for anxiety, 34% (n = 13) for depression, 21% (n = 8) for PTSD, and 5% (n = 2) for addiction to a different substance. In our sample, no responses reflected use for psychotic symptoms.
A Pearson correlation between total AUDIT and CUDIT-R scores (n = 308) was not significant (r = 0.08, P = 0.150). A t test comparing total AUDIT scores between cannabis users and nonusers was significant, t(530.11) = −7.26, P < 0.001, (users: M = 5.52, SD = 5.50; nonusers: M = 2.86, SD = 4.21). Cannabis users reported significantly more symptoms of AUD than nonusers, despite differences on demographic factors of age, ethnicity, and education. Hierarchical linear regression analyses showed that these demographic factors did not account for a significant proportion of the variance in AUDIT scores, strengthening confidence that this group difference is not best explained by demographic differences between users and nonusers. In cannabis users (n = 308), correlations between the total AUDIT and DASS-21 stress score (r = 0.09, P = 0.120) and anxiety score (r = 0.076, P = 0.182) were not significant. A significant positive correlation was found between the AUDIT and DASS-21 total score (r = 0.14, P = 0.018) and depression score of the DASS-21 (r = 0.17, P = 0.002) representing a small effect size. In cannabis nonusers (n = 487), correlations between the AUDIT and DASS-21 total score (r = 0.09, P = 0.056), depression score (r = 0.07, P = 0.139) and anxiety score (r = 0.05, P = 0.250) were not significant. There was a small but significant Pearson correlation between the AUDIT and stress subscale scores (r = 0.11, P = 0.016). These results suggest that generally, alcohol use is not significantly related to symptoms of distress; however, it is differentially related to depressive symptoms in cannabis users and stress symptoms in nonusers.
To our knowledge, this is the first study to describe patterns of cannabis use in a large sample of patients seeking treatment for anxiety and related disorders. Cannabis users and nonusers differed demographically on education level, age, and ethnicity. Nonusers were generally older; this may be because cannabis tends to be used in adolescence and young adulthood rather than later in life.27 It appears that cannabis users generally have lower levels of education which may be related to the cognitive and behavioural effects of cannabis (e.g., reduces attention, memory, and behavioural motivation),16,28 which could impede academic performance. Given that those with lower education levels tend to discount larger later rewards for smaller more immediate rewards, it is possible that these individuals are more likely to manage their anxiety with cannabis, which provides short term-immediate relief but adverse health consequences, than other means.29,30
Consistent with previous research that demonstrates a positive association between cannabis use and anxiety,4 rates of cannabis use were high in this population, with 39% of patients endorsing having used cannabis in the past 6 months, whereas only 29% of Canadians ages 16 and older have reported using cannabis in the past 12 months.2 A large portion of cannabis users in the current sample (43%) reported using 4 or more times per week, most commonly via smoking joints. The majority of patients did not screen positive for CUD on the CUDIT-R and reported using only an average of 0.53 g on a day they use cannabis, which is less than recreational users who use 1.6 g on average.31 Thus, the vast majority of cannabis users in our sample do not report problems with the amount or severity of their use. However, 22% of the current sample scored above the cutoff score on the CUDIT-R, indicating likely CUD. This rate is elevated given that the 12-month prevalence rate of CUD in the general population is approximately 3.5% in men and 1.7% in women.3 Therefore, while the majority of clients in an anxiety clinic who use cannabis may not report any difficulties associated with their use, 1 in 5 of these individuals likely do as they report scores equal to or greater than 13 on the CUDIT-R.
Based on the tension-reduction model, which suggests that substances are used to reduce distress, we hypothesized that this population may use cannabis to cope with their distress. Our results found indirect support for this hypothesis. Overall symptoms of psychological distress (total DASS-21 scores) were significantly and positively correlated with the severity of CUD symptoms (total CUDIT-R scores). Further, stress, anxiety, and depression symptoms (represented by DASS-21 subscales), were also significantly and positively correlated with the severity of CUD symptoms. Although we cannot comment on the direction of this relationship, if high distress is prompting cannabis use, this may explain the elevated rates of cannabis use in this population. In addition, of the 53 patients who answered additional cannabis-related questions, 45% of users reported using cannabis for medicinal reasons (i.e., medical or psychiatric), suggesting that a significant proportion of users in this population identify using cannabis to cope with psychiatric and medical forms of distress. Interestingly, most individuals did not provide an answer as to whether or not they have a prescription for cannabis. It is possible that patients consider their cannabis use to be “medicinal” as they believe it provides relief from mental or physical illness, but do not have a prescription. As such, they may feel that there is stigma related to using cannabis without the recommendation of a doctor for their ailments and therefore, feel uncomfortable answering this question. Nineteen percent endorsed using for psychiatric reasons and 21% endorsed using to aid sleep (which may be as a result of psychiatric illness such as anxiety, depression, or PTSD).32 These findings suggest that some patients who use cannabis may specifically use to cope with mental health symptoms. The reasons for initial cannabis use, which occurs on average in adolescence in this population, remain unclear. It may be that cannabis was initially used to cope with mental health symptoms at their onset (which also tend to begin in adolescence and young adulthood).33 It may also be that cannabis was used for social and enhancement motives in adolescence, which may have increased their risk of later mental health concerns or CUD, at which point the motives for use may have changed to coping.19,33,34 Further research should examine the temporal relationship between mental health concerns and age of first use. Collectively, these results are in line with the tension-reduction model in the context of cannabis use because distress ratings and CUD symptoms were significantly positively correlated; further research could examine the direction of this relationship.
Contrary to our expectations, not all correlations between total AUD symptoms and severity of distress in cannabis users and cannabis nonusers were significant and positive. There were nonsignificant correlations between AUD symptoms and symptoms of stress and anxiety, however there was a significant correlation between AUD and distress in general, as well as depression symptoms in cannabis users, and between AUD symptoms and stress in cannabis nonusers. It may be that alcohol is not used to reduce anxiety- and stress-related distress in this sample, but that it may be used specifically to cope with depressive symptoms in cannabis users and with stress in cannabis nonusers. However, it could be that alcohol use is related to more distress as a result of the harmful consequences of alcohol use (e.g., alcohol use causing relationship problems which leads to greater distress). The direction of this relationship is not clear in the present study. Further, there was no correlation between severity of CUD and AUD; however, cannabis users were significantly more likely to exceed the cut off score suggestive of AUD. In other words, those who use cannabis at an elevated rate do not necessarily use alcohol at an elevated rate but cannabis-users in general are more likely to abuse alcohol than nonusers. These results suggest that there may be other factors at play in the decision to use cannabis rather than alcohol. It may be that individuals who use any amount of cannabis have personality factors that increase their likelihood of addiction to multiple substances (e.g., impulsivity)35,36 or that cannabis and alcohol are used together to varying degrees.37 Further research should examine other potential factors involved in the decision to use cannabis specifically rather than other substances to reduce distress.
The current findings have important clinical implications. Given the elevated rate of cannabis use in patients seeking treatment for anxiety and related disorders, clinicians may want to carefully screen for CUD when clients present with anxiety symptoms to provide optimal treatment recommendations. In this screening, idiosyncratic reasons for cannabis use can be determined that may have implications for therapy. For example, if clients are using cannabis to manage anxiety (e.g., cannabis use as a safety behaviour), this can be addressed in a cognitive behaviour therapy (CBT) protocol. Further, given that CBT is both cognitively and behaviourally demanding and cannabis use impedes cognitive functioning (e.g., reduces attention, memory) and behavioural motivation,16,28 patients using at high amounts and frequencies may not be able to optimize their treatment outcomes for anxiety while using cannabis. Therefore, it may be optimal for patients to complete CUD treatment before CBT for anxiety or also consider reducing cannabis use as they engage in treatment for their anxiety and related symptoms. Moreover, clinicians may consider recommending integrated treatment for anxiety and CUD whereby both problems are treated simultaneously with focus on the functional relationship between symptoms.38 Future studies should examine the effect of cannabis use on treatment outcomes.
Limitations of this study include that the sample is ethnically homogeneous in that it is predominantly Caucasian. Future research should examine these patterns across cultural and racial groups, as there may be important differences.39 Some differences in cannabis use have been identified; for example, some research shows African-Americans’ highest rate of cannabis use is later compared to other racial groups (i.e., late 20s)27 and that African-American women are 3 times more likely to use cannabis for the first time before alcohol compared to European-Americans and are at greater risk of cannabis-related problems.40 Further research is warranted to identify which groups are at highest risk of cannabis-related problems and anxiety symptoms. In addition, there is a lack of full demographic (e.g., income, employment, lifetime history of cannabis use) and diagnostic data in this sample. Although these patients had elevated scores on the anxiety subscale of the DASS-21, indicating the presence of significant anxiety symptoms, detailed diagnostic information would be helpful to fully describe this sample. It may be that patients’ patterns of cannabis use vary across type of anxiety disorder or that patients with some disorders are at greater risk of using cannabis at a higher rate than others. Future research could compare patterns of cannabis use and motives for use across specific anxiety and related disorders as there may be unique patterns within specific diagnostic groups. In addition, we did not collect data in a sample of healthy controls, which would provide base rates of cannabis use and characteristics of use in a healthy sample. The present study also relied on self-report data rather than biological data (e.g., urine samples). As a result, patients may have misrepresented their use (e.g., under-reported their use).
In summary, the results suggest that cannabis use is prevalent in those seeking therapy for anxiety and related disorders and is related to several indicators of psychological distress. Severity of cannabis use and alcohol use was not correlated, suggesting that there may be other factors moderating substance use (e.g., impulsivity).35,36 Considering the recent legalization of cannabis use in Canada, reports of problematic cannabis use in this population may continue to increase; this study provides an important baseline snapshot of cannabis use around the time of legalization in a large sample of patients seeking specialized treatment for anxiety symptoms. Future research should focus on examining patterns of cannabis use more closely across specific mental health diagnoses to determine whether or not there are populations at particularly high risk of CUD, investigating the causality of the relationship between cannabis use and symptom severity, and systematically studying the impact of cannabis use and CUD on treatment outcomes for anxiety disorders.
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