The American Journal on Addictions, 23: 485–492, 2014 Copyright © American Academy of Addiction Psychiatry ISSN: 1055-0496 print / 1521-0391 online DOI: 10.1111/j.1521-0391.2014.12135.x
Physical Activity and Cannabis Cessation Jessica G. Irons, PhD,1 Kimberly A. Babson, PhD,2,3 Cecilia L. Bergeria, BA,4 Marcel O. Bonn‐Miller, PhD2,5,6,7 1
Department of Psychology, James Madison University, Harrisonburg, Virginia Center for Innovation to Implementation, VA Palo Alto Health Care System, Menlo Park, California 3 Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Menlo Park, California 4 University of Vermont, Burlington, Vermont 5 National Center for PTSD, VA Palo Alto Health Care System, Menlo Park, California 6 Center of Excellence in Substance Abuse Treatment and Education, Philadelphia VA Medical Center, Philadelphia, Pennsylvania 7 Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 2
Background and Objectives: Based on recent empirical and theoretical work suggesting that physical activity (PA) activates many of the same physiological systems as cannabis, the present study sought to investigate the impact of PA level (ie, low [including none] vs. moderate/high) on a cannabis cessation attempt during the first 7 days post‐quit. Methods: The present study was a 2 time‐point prospective study of 84 cannabis dependent military veterans (3 female) who responded to study flyers, within a Veterans Affairs Medical Center, seeking individuals interested in engaging in a self‐guided cessation attempt. All study measures were self‐report. Results: Though no baseline differences between those with low and those with moderate/high levels of physical activity were observed, results revealed that participants who reported low levels of physical activity, versus moderate/high levels, were significantly more likely to report a cannabis lapse during the week following a quit attempt, particularly within the first 4 days of the cessation period. Further, individuals with low levels of PA were also more likely to report greater mean cannabis use during the first 4 days of the cessation period. Conclusions and Scientific Significance: Findings suggest that early interventions aimed at increasing physical activity may be useful among individuals with cannabis dependence who are engaged in a cessation attempt. (Am J Addict 2014;23:485–492)
Cannabis is the most widely used illicit drug in the United States1 and may lead to a variety of detrimental effects including, but not limited to, impairment while driving, carcinogenic exposure when smoked, and a decrease in motivation for activities that were once rewarding.2 Over time, chronic cannabis use leads to tolerance,3 with individuals who discontinue use after the development of tolerance experienc-
Received June 21, 2013; revised November 17, 2013; accepted November 23, 2013. Address correspondence to Dr. Irons, Department of Psychology, MSC 7704, James Madison University, Harrisonburg, VA 22807. E‐mail: [email protected].
ing symptoms of withdrawal, including cravings, irritability, sleep difficulties, and anxiety.4 Following, there has been consistent documentation of difficulty quitting among cannabis dependent individuals, regardless of motivation or treatment employed.5 Though current cultural and political trends push for its legalization, much remains to be understood about the drug and the full extent of cannabis’ effects, both detrimental and beneficial. Administration of the psychoactive component of cannabis (ie, delta‐9‐tetrahydrocannabinol; THC), activates the endocannabinoid system in the brain.6 With respect to endocannabinoid activation, cannabis use produces similar physiological events to physical activity (PA). For example, the “runner’s high,” previously thought to be primarily related to endorphins, has been linked to endocannabinoid activity, suggesting that endocannabinoids may play a role in the euphoric experience as a result of PA.7 Effects from the “runners high” include, but are not limited to, a reduction in anxiety and difficulties in estimating the passage of time.8,9 Endocannabinoids (unlike endorphins) are also effective at producing analgesic effects at central and peripheral nervous system locations and facilitating blood flow and respiration.10 To the extent that use of cannabis and engaging in PA lead to similar biological events it is possible that one behavior may function to substitute for the other, at least physiologically. Recent research suggests that engaging in intervention tactics that influence the endocannabinoid system for individuals with cannabis dependence may be effective.11 As discussed earlier, as aerobic PA has been shown to produce release of endocannabinoids (eg, anandamide), one strategy for activating the endocannabinoid system is engagement in PA. Recent studies have confirmed the activation of endogenous endocannabinoids as a result of moderate and high intensity levels of PA.12,13 Specifically, Sparling et al.12 found that participants who engaged in PA (ie, ran) for 50 minutes at moderate levels of intensity yielded elevated levels of 485
anandamide in blood samples compared to sedentary controls. These findings suggest that aerobic PA may be used as an intervention to influence cannabis use. Given that PA is associated with activity in the endocannabinoid system, it may lend itself well to abate withdrawal symptoms following a cessation attempt. Consistent with this notion, basic researchers have suggested that providing alternative ways of activating the endocannabinoid system may be a fruitful avenue for treating cannabis dependence.11 Recent studies suggest that greater participation in sports and PA is associated with lower levels of cannabis use, and conversely, decreased PA has been associated with greater use of cannabis.14–16 A recent study showed that a PA intervention involving a 1‐week adjustment period followed by ten 30‐ minute PA sessions (with target of 60% maximum heart rate) resulted in significant reductions in both cannabis craving and cannabis use during the intervention period and for the duration of the 2‐week follow‐up period.17 Once the PA intervention was removed, however, cannabis use returned toward pre‐treatment levels, suggesting that PA may have been a substitution for cannabis use, but only for the duration of the intervention. A similar line of work has suggested that PA reduces nicotine craving and improves nicotine cessation outcomes.18,19 While past research has found a relation between PA and cannabis use, the particulars of the influence of PA on cannabis use remains to be thoroughly investigated. The current study aims to examine the relation between PA levels and cannabis use following a self‐guided cannabis cessation attempt among dependent veterans. Veterans were a focus of this investigation because they represent a group that has evidenced marked increases in cannabis use disorder diagnoses over the past decade, and high rates of co‐occurring psychological disorders, with little to no sign of abatement.20 Based on recent work,17 it was hypothesized that individuals who reported a routine of moderate/high levels of PA immediately prior to a self‐guided quit attempt would have reduced rates of cannabis use, as well as reduced incidence of lapse (defined as any post‐cessation cannabis use21), as compared to those who engaged in PA at low levels (including those who engaged in zero PA). We chose to examine the association between PA and cannabis cessation outcomes among military veterans as recent evidence suggests a growing need for cannabis interventions among this population.20
METHOD Participants Participants were recruited via advertisements, targeting veterans interested in making a cannabis cessation attempt, which were placed throughout a VA medical center. The current sample included 84 cannabis dependent veterans (3 female; Mage ¼ 50.96 years, SD ¼ 10.07) from a larger parent study of 102 cannabis dependent veterans that examined factors impacting cannabis cessation success.22 The present sample was selected from the parent study as these individuals 486
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had complete data for all assessments over the first week of the cannabis cessation attempt. All study procedures were approved by the Institutional Review Boards (IRBs) of the VA Palo Alto Health Care System and Stanford University. Study inclusion criteria involved (1) being a U.S. veteran as assessed by the VA, (2) meeting diagnostic criteria for current cannabis dependence based on DSM‐5 criteria, (3) reporting a current level of motivation to quit of at least 5 on a 10 point scale (0 ¼ no interest in quitting to 10 ¼ definite interest in quitting), and (4) being interested in making a serious self‐ guided quit attempt. Individuals were excluded for the following reasons: (1) inability to provide informed, voluntary, written consent to participate, (2) having a significant decrease (of >25%) in amount of cannabis used per day during the previous month, and (3) currently pregnant or breastfeeding. Measures Baseline Characteristics AXIS‐I Diagnostic Status. Current Axis I diagnostic status (except posttraumatic stress disorder) was assessed via the Structured Clinical Interview‐Non‐Patient Version for DSM‐ IV (SCID I‐N/P23).1 The Clinician Administered PTSD Scale (CAPS25) is a well‐established semi‐structure interview that was used to determine diagnostic status of posttraumatic stress disorder (PTSD). Trained study staff conducted the SCID I‐N/ P and CAPS during the baseline assessment. All interviews were audio‐recorded and diagnoses were confirmed by the last author following a review of recorded interviews. Motivation to Quit Cannabis. Participants’ motivation to quit cannabis was assessed during baseline using an adapted version of the Contemplation Ladder (CL26). The CL is a visual analogue scale (VAS) comprised of 10 steps, each with a corresponding statement assessing motivation to quit cannabis. Items range from, 1 ¼ “I enjoy using marijuana and have decided not to quit using marijuana for my lifetime,” to 10 ¼ “I have quit using marijuana and I will never use again,” with 5 indicating “I often think about quitting using marijuana.” Depression Symptoms. The Beck Depression Inventory‐II (BDI‐II27) is a 21‐item measure that was administered at baseline to determine symptom severity of depression (Cronbach’s a ¼ .92). Positive and Negative Affect. The Positive and Negative Affect Schedule (PANAS28) is a 20‐item questionnaire that provides an index of general affect divided into two dimensions: positive and negative affect. The PANAS was delivered during the baseline assessment. Cronbach’s a ¼ .91 (positive affect), .93 (negative affect) for the current sample. Problematic Substance Use. Problematic cannabis use was assessed at baseline using the Marijuana Problems Scale (MPS29). This 19‐item scale is used to assess the negative social, occupational, physical, and personal consequences of cannabis use within the past 90 days. A total overall score was 1
The employed diagnostic criteria for cannabis dependence were consistent with the definition set forth in the DSM‐IV‐TR 24, with the addition of withdrawal, as proposed for DSM‐5 4. September–October 2014
used to index severity (Cronbach’s a ¼ .94). Problematic tobacco use was assessed using the 7‐item Fagerström Test for Nicotine Dependence (FTND30). A sum score was used to index overall severity (Cronbach’s a ¼ .75). Problematic alcohol use was assessed via the 10‐item Alcohol Use Disorders Identification test (AUDIT31). A total score was used as an overall index of severity (Cronbach’s a ¼ .93). Cannabis Motives. The Marijuana Motives Measure (MMM32) was used to assess motives for using cannabis. The MMM is a 25‐item measure used to assess 5 motives for use including: conformity (eg, “Because my friends pressure me to use marijuana,” expansion (eg, “To know myself better”), enhancement (eg, “Because it’s exciting”), coping (eg, “To forget my worries”), and social reasons (eg, “To be sociable”). In the current study Cronbach’s a ¼ .87 (conformity), .91 (expansion), .81 (enhancement), .83 (coping), and .87 (social). Cannabis Craving. Craving for cannabis was assessed using the 17‐item Marijuana Craving Questionnaire (MCQ33), which yields four factors: compulsivity (eg, unable to control cannabis use), emotionality (eg, use cannabis in anticipation of relieving emotional distress), expectancy (eg, anticipate a positive outcome), and purposefulness (eg, intention and planning to use). Within the current study Cronbach’s a ¼ .53 (compulsivity), .82 (emotionality), .76 (expectancy), and .75 (purposefulness). Readiness to change. Motivation and readiness to change cannabis use was assessed using the University of Rhode Island Change Assessment (URICA34). This 32‐item measure yields a sum score of overall level of readiness to change (Cronbach’s a ¼ .82). Primary Variables Physical Activity. The 4‐item International Physical Activity Questionnaire—Short Form (IPAQ‐SF35) was used to assess levels of physical activity. Participants are asked how many days/week and minutes/day they engaged in (1) high activity (ie, physically challenging activities that makes an individual breath much harder than normal); (2) moderate activity (ie, moderate level of physical activity that moderately increases breathing); (3) walking for at least 10‐minutes; and (4) sedentary activity (ie, sitting). Consistent with recommendations, data were cleaned of missing and out‐ of‐range values prior to scoring. Therefore, all individuals included in the current study had complete and reliable PA data. Metabolic equivalents (METS) minutes/week were calculated for walking, moderate, and high‐level activity. Categories of level of activity were then developed based on established scoring rules.35 For the purposes of the present study, moderate and high level activity were combined to make one group, based on existing literature demonstrating no clear differences between these two groups in terms of substance use outcomes.36,37 Those with low (including zero35) physical activity were within the second group. Validity studies indicated a high positive correlation with an activity monitor and the IPAQ data.38 IPAQ data were collected at baseline only. Irons et al.
Substance Use and Lapse. The Timeline Follow‐back interview (TLFB39) was administered at baseline to obtain frequency and quantity of cannabis, tobacco, and alcohol use over the course of the 90‐days prior to the cannabis quit attempt. The TLFB was also administered at one‐week post‐ quit to obtain substance use data for the week following the quit attempt. Quantity of cannabis used on each day was indexed by a graphical depiction that ranged from 0 to 8.40 Cannabis use information from the TLFB was used to determine lapse (defined as any use), and frequency/quantity of use at each of the 7 days post‐quit. The TLFB procedure has demonstrated good reliability and validity in past work across diverse samples,39 and has been demonstrated to be a reliable and valid indicator of cannabis use.41 Procedure Interested individuals contacted the research team and were provided with a description of the study over the phone and completed a preliminary phone‐based screening for initial eligibility. Those eligible scheduled a baseline appointment for one day prior to the day they were willing to make a serious self‐guided cannabis quit attempt. During this baseline appointment individuals completed informed consent procedures. Research staff then administered the SCID I‐ NP23 and CAPS25 to assess for psychopathology, with those remaining eligible then completing the TLFB39 and a battery of self‐report measures. Individuals were then compensated $75 for their time and instructed to make a serious cannabis quit attempt the next morning. Participants then returned for a follow‐up assessment 7 days following their quit day, when they again completed the TLFB39. At the end of the follow‐up appointment, participants were compensated $15 for their time. Data Analytic Approach Prior to the primary data analysis we examined the relations between PA and participant demographic and baseline characteristics via t‐tests (continuous variables) and chi‐square analyses (categorical variables), for descriptive purposes. Next, we sought to examine the relation between PA and both lapse and mean use of cannabis within each day of the first week of the quit attempt. In order to examine the impact of PA on lapse, we employed a Cox regression with time‐dependent covariates, as we expected PA would have a time‐dependent effect on lapse. Within this model, PA was entered as a time‐ dependent categorical variable. Lapse (yes/no) was entered as the censoring variable (1 indicating the event occurred), and covariates included baseline cannabis, alcohol, and tobacco use, and mean alcohol and tobacco use over the course of the quit week. In order to determine the impact of PA on lapse by each day of the quit attempt, we then conducted a series of logistic regressions. Here, lapse (yes/no) by each day (1 though 7) was entered within separate models (7 total analyses). PA (modeled categorically) was entered as the independent variable, and covariates included baseline cannabis, alcohol, and tobacco use, and mean alcohol and tobacco use for the days
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prior to and including the day of the lapse outcome (ie, Day 3 analyses included mean alcohol and tobacco use for Days 1–3). We examined the relation between PA (modeled categorically) and mean cannabis use within each day of the first week of the quit attempt using a series of t‐tests. Level of PA (low vs. moderate/ high) was entered as the between group variable with mean cannabis use by each of the first 7 days included as the outcome within 7 separate analyses. Alpha level was adjusted for multiple comparisons for all t‐tests using a Bonferroni correction (alpha ¼ .007).
ing in PA at low levels compared to moderate/high levels were not significantly different in terms of (a) problematic cannabis, alcohol, or tobacco use; (b) total cannabis, alcohol, and tobacco use during baseline; (c) daily use of cannabis, alcohol, and tobacco during baseline; (d) cannabis motives; (e) cannabis craving; (f) readiness for change; (g) or affect including positive and negative affect, and depression (see Table 2). In terms of rates of lapse during the first week of the quit attempt, 38.10% lapsed by Day 1, 46.40% by Day 2, 54.80% by Day 3, 57.10% by Day 4, 60.50% by Day 5, 61.90% by Day 6, and 65.50% lapsed by Day 7.
RESULTS
Physical Activity and Cannabis Use Outcomes: Lapse Results suggested that individuals engaging in low versus moderate/high levels of PA had greater risk for lapse over the course of the quit attempt after accounting for baseline cannabis, alcohol, and tobacco use, and mean alcohol and tobacco use over the course of the week, HR ¼ 4.42, 95% CI: 1.47–13.26. Logistic regressions suggested that individuals engaging in low versus moderate/high levels of PA had greater risk for lapse by Days 1–4, but not Days 5–7, after accounting for covariates (see Fig. 1 and Table 3).
Associations Between Physical Activity and Participant Characteristics On average, participants reported using cannabis regularly for 28.31 (SD ¼ 13.59) years. Table 1 provides an overview of participant characteristics in relation to demographic, substance use, and diagnostic status. In addition, we examined the association between PA and baseline characteristics in relation to substance use, readiness for change, and affect for descriptive purposes. Results demonstrated that those engag-
TABLE 1. Demographic information as a function of level of physical activity
Variable Age Gender (female) Employment Employed/retired Unemployed Ethnicity Caucasian African American Latino/Hispanic Asian/other Marital status Married Divorced Widowed Never married Education Some H.S. H.S. graduate Some college or more AXIS 1 diagnoses (current) Alcohol dependence Any depression Any anxiety PTSD
Low level M (SD) or N (%)
Moderate/high level M (SD) or N (%)
p‐Value
52.42 (6.36) 3 (11.1%)
50.27 (11.4%) 1 (1.75%)
.281 .060 .521
21 (77.8%) 6 (22.2%)
49 (85.9%) 8 (14.1%)
9 16 2 0
(33.3%) (59.3%) (7.4%) (0.0%)
23 14 10 10
(40.4%) (24.6%) (17.5%) (17.5%)
8 13 2 3
(30.8%) (50.0%) (7.7%) (11.5%)
11 23 2 18
(20.4%) (42.6%) (3.7%) (33.3%)
.536
.306
.549 1 (3.7%) 4 (14.8%) 22 (81.5%)
4 (7.0%) 10 (17.5%) 43 (75.5%)
6 4 10 12
13 11 19 20
(22.2%) (14.81%) (37.0%) (44.4%)
(22.8%) (19.3%) (33.3%) (35.1%)
.952 .616 .739 .410
M, mean; SD, standard deviation; H.S., high school; Axis 1 diagnoses were based on DSM‐IV criteria and were assessed via the Structured Clinical Interview for DSM‐IV (SCID‐NP; 23); any depression includes major depressive episode, major depressive disorder, and dysthymia; any anxiety includes panic disorder, generalized anxiety disorder, social anxiety disorder, obsessive compulsive disorder; PTSD, posttraumatic stress disorder.
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TABLE 2. Baseline characteristics as a function of level of physical activity
Variable Problematic substance use Cannabis Tobacco Alcohol Total use during 90 d of baseline Cannabis Tobacco Alcohol Amount of use/d of baseline Cannabis Tobacco Alcohol Cannabis motives Enhancement Social Conformity Expansion Coping Cannabis craving Compulsive Emotional Expectancy Purposeful Readiness to change Readiness for change Affect Positive Negative Depression
Low level, M (SD) or N (%)
Moderate/high level, M (SD) or N (%)
Range
p‐Value
7.99 (9.16) 2.94 (1.39) 17.64 (13.37)
10.00 (9.41) 2.80 (1.09) 12.80 (11.71)
0–37 0–5 0–45
.669 .702 .105
529.37 (164.33) 670.85 (734.58) 256.78 (417.15)
476.52 (198.77) 486.66 (718.19) 173.00 (487.13)
135–720 0–2720 0–2927
.235 .280 .445
6.02 (1.71) 12.07 (7.47) 6.00 (5.36)
6.03 (2.03) 10.68 (8.24) 4.68 (6.81)
1–8 0–30 0–34
.963 .566 .473
3.98 3.38 1.67 2.63 3.47
(0.78) (1.27) (1.03) (1.33) (1.12)
3.49 2.91 1.76 2.56 3.21
(1.09) (1.09) (0.92) (1.17) (1.25)
1–5 1–5 1–5 1–5 1–5
.038 .079 .689 .812 .342
9.07 11.48 12.96 13.09
(4.76) (5.94) (5.52) (5.61)
8.28 10.56 11.47 11.92
(4.34) (5.19) (5.37) (5.24)
3–21 3–21 3–21 3–21
.455 .473 .244 .353
9.22 (2.19)
8.57 (1.80)
0–13
.150
32.35 (10.45) 21.73 (9.18) 17.78 (12.34)
32.12 (8.41) 22.98 (10.22) 17.71 (12.27)
0–50 0–50 0–51
.919 .596 .980
Problematic substance use: cannabis (Marijuana Problems Scale), tobacco (Fagerstrom Test for Nicotine Dependence), Alcohol (Alcohol Use Disorder Identification Test; Total use and amount of use per day for alcohol, tobacco, and cannabis were determined through the Timeline Follow Back; Cannabis motives was assessed via the Marijuana Motives Scale; Cannabis craving was assessed via the Marijuana Craving Scale; Readiness to change was assessed through the University of Rhode Island Change Assessment; Positive and negative affect were assessed through the Positive and Negative Affect Schedule; Depression was assessed via the Beck Depression Inventory.
Physical Activity and Cannabis Use Outcomes: Mean Use A series of t‐tests demonstrated that PA (low levels versus moderate/high levels) was associated with mean cannabis use for Days 1–4 of the quit attempt. Specifically, for Days 1–4, individuals with low levels of PA had greater mean cannabis use compared to those engaging in PA at moderate/high levels (see Table 3).
DISCUSSION The current study demonstrates that cannabis dependent veterans who self‐reported engaging in PA at moderate/high levels exhibit lower rates of lapse during the first 4 days following a self‐guided quit attempt, as compared to those who reported low levels or not engaging in PA. Furthermore, Irons et al.
participants who reported moderate/high PA had lower cumulative mean cannabis use on Days 1–4 post‐quit. Baseline characteristics (eg, substance use, affect) were similar for participants who reported moderate/high levels of PA and those who reported low levels or no PA. These data support the notion that PA may have advantageous effects with respect to cannabis use and lapse and thus may be a potential early intervention strategy for cannabis users. Incidence of cannabis lapse is predictive of subsequent relapse such that early intervention is critical.42 Taken together, the current study data and previous work, suggesting that a PA intervention may serve to reduce cannabis use,17 provide compelling evidence of the putative benefits of engaging in moderate/high PA as an intervention for individuals with cannabis dependence. Further studies are necessary to fully elucidate the conditions under which PA may improve cannabis use rates (eg, as a stand‐alone intervention or
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symptoms peak by the third day following a cessation attempt.44 Indeed, it is possible that PA is most relevant during periods of heightened withdrawal, while other factors (eg, social support45) may be more important for long‐term quit success. Future studies might specifically consider the role of PA in reducing cannabis use as a function of abating or delaying withdrawal symptoms. The present study findings are consistent with previous work examining the relation between PA and cannabis use; however, there are several limitations to consider. Though PA may act as a putative substitute for cannabis use, other possibilities remain unexamined. For example, PA could function as a complement (additively or multiplicatively) to the cannabis high, such that use is maintained more readily. It is also possible that PA and cannabis use have no measureable effects on one another (and previous studies represent Type I error or results confounded by extraneous influences). Further, there may be unidentified mechanisms by which PA may influence substance use generally, and not cannabis specifically. Additional limitations related to sample characteristics must be considered. Our sample consisted of heavy substance using veterans interested in engaging in a self‐guided cessation attempt. Our homogenous sample provides great insight about a vulnerable population with respect to substance dependence; however, it remains to be seen if our findings will generalize to other populations. For example, while our gender distribution is consistent with the veteran population, additional research should examine findings among more gender diverse samples. Additionally, our PA data do not allow for insight into potential relative benefits of different types of activity (eg, running relative to walking or weight lifting) such that future research might consider additional measures related to physical activities. Further, our use of self‐report to gather data related to PA poses a potential limitation and future research might consider objective measures of PA. In addition, our comparisons are quasi‐experimental in nature and our study was of a short duration such that causal inference is further limited. Understanding of the effects of PA on cannabis use will
FIGURE 1. The percent of individuals lapsing by each day of the first week of a cannabis quit attempt as a function of level of physical activity (low vs. moderate/high). Stars indicate significant differences at p < .05.
as an adjunct to other treatment efforts) as well as for whom such an intervention might be most effective (eg, among those with anxiety or coping‐oriented cannabis use43). In addition, studies will need to examine how best to implement a PA intervention (eg, intensity, frequency, and/or duration of time spent engaged in PA; cardiovascular versus anaerobic work) to maximize benefit and minimize harm (eg, protect previously sedentary individuals from injury). It is unclear why differences in lapse rates and mean use between those who reported moderate/high levels of PA and those who reported low levels or no PA occurred only within the first 4 days following a quit attempt. At least 2 possible explanations warrant further examination. First, as PAwas only measured immediately pre‐cessation, it is possible that as time progressed, participant PA level changed, thus rendering baseline levels progressively less predictive over time. Alternatively, this pattern of findings may be related to the experience of withdrawal symptoms; most salient withdrawal
TABLE 3. Mean use and lapse per day as a function of low and high levels of physical activity
Day(s) 1 1–2 1–3 1–4 1–5 1–6 1–7
Low PA
Moderate/high PA
M (SD)
M (SD)
2.96 2.98 2.97 2.88 2.78 2.79 2.79
(3.05) (3.06) (2.99) (2.95) (2.88) (2.82) (2.80)
1.14 1.21 1.32 1.35 1.41 1.42 1.42
(2.08) (1.83) (1.81) (1.82) (1.74) (1.73) (1.68)
Mean use
Lapse
t
p‐Value
Day
OR
95% CI
p‐Value
3.20 3.28 3.12 2.91 2.70 2.74 2.70
.002 .001 .002 .005 .008 .007 .008
1 2 3 4 5 6 7
.14 .18 .21 .02 .31 .33 .42
.04–.46 .05–.59 .06–.67 .07–.77 .09–1.02 .11–1.04 .13–1.36
.001 .005 .009 .016 .054 .058 .149
Low PA, low level of physical activity; Moderate/high PA, moderate or high level of physical activity. Statistically significant at p < .05. Statistically significant at p < .007, accounting for Bonferroni correction.
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benefit from a randomized controlled trial including baseline, intervention, and follow‐up measures of both cannabis use and PA. Together, the present study served as the first prospective empirical investigation of the impact of PA on cannabis cessation outcomes among military veterans. The capacity of PA to delay or prevent withdrawal symptoms upon cannabis cessation may serve as a viable complement to existing intervention strategies, if not as a standalone intervention for dependent use. Further, given the increasing rates of cannabis use disorder diagnoses among veterans,20 the use of PA interventions as complements to existing cannabis use disorder treatments within the Veterans Administration may be warranted. Additional experimental studies examining the effects of PA on cannabis use are necessary to confirm (or disconfirm) these ideas as well as add to our understanding of effects over time and across populations, contexts, and differing levels of cannabis use. This work was supported, in part, by A VA Clinical Science Research and Development (CSR&D) Career Development Award—2 (Bonn‐Miller), and VA Health Services Research and Development Service funds (Babson). The expressed views do not necessarily represent those of the Department of Veterans Affairs. Declaration of Interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this paper.
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Irons et al.
11. Clapper J, Mangieri R, Piomelli D. The endocannabinoid system as a target for the treatment of cannabis dependence. Neuropharmacology. 2009;56: 235–243. 12. Sparling P, Giuffrida A, Piomello D, et al. Exercise activates the endocannabinoid system. Cog Neurosci. 2003;14:1–3. 13. Heyman E, Gamelin FX, Goekint M, et al. Intense exercise increases circulating endocannabinoid and BDNF levels in humans—possible implications for rewards and depression. Psychoneuroendocrinology. 2012;37:844–851. 14. Pate RR, Heath GW, Dowda M, et al. Associations between physical activity and other health behaviors in a representative sample of US adolescents. Am J Public Health. 1996;86:1577–1581. 15. Terry‐McElrath Y, O’Malley P, Johnston L. Exercise and substance use among American youth, 1991–2009. Am J Prev Med. 2011;40:530–540. 16. Werch CC, Moore MJ, DiClemente CC, et al. A multi‐health behavior intervention integrating physical activity and substance use prevention for adolescents. Prev Sci. 2005;6:213–226. 17. Buchowski M, Meade N, Charboneau E, et al. Aerobic exercise training reduces cannabis craving,use in non‐treatment seeking cannabis‐dependent adults. PLoS ONE 2011;6:e1746. 18. Haasova M, Warren FC, Ussher M, et al. 2013; The acute effects of physical activity on cigarette cravings: systematic review and meta‐analysis with individual participant data. Addiction (Abingdon, England) 108:26–37. 19. Williams DM, Whiteley JA, Dunsiger S, et al. 2010. Moderate intensity exercise as an adjunct to standard smoking cessation treatment for women: A pilot study. Psychol Addict Behav. 24:349–354. 20. Bonn‐Miller MO, Harris A, Trafton JA. Prevalence of cannabis use disorder diagnoses among veterans in 2002, 2008, and 2009. Psychol Serv. 2012;9:404–416. 21. Marlatt A, Gordon R. Relapse Prevention: Maintenance Strategies in the Treatment of Additive Behavior. New York, NY: Guilford Press; 1985. 22. Heinz AJ, Peters EN, Boden MT, et al. A comprehensive examination of delay discounting in a clinical sample of cannabis‐dependent military veterans making a self‐guided quit attempt. Exp Clin Psychopharmacol. 2013;21:55–65. 23. First MB, Spitzer RL, Gibbon M, et al. Structured Clinical Interview for DSM‐IV (SCID‐I) (User’s Guide and Interview), research version. New York, NY: Biometrics Research Department, New York Psychiatric Institute; 1995. 24. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th edn, text revision. Washington, DC: American Psychiatric Association; 2000. 25. Blake D, Weathers F, Nagy L, et al. The development of a clinician‐ administered PTSD scale. J Trauma Stress. 1995;8:75–90. 26. Prochaska JO, DiClemente CC. Stages and processes of self‐change of smoking. Toward an integrative model of change. J Consult Clin Psychol. 1983;51:390–395. 27. Beck A, Steer R, Brown G. Manual for the Beck Depression Inventory‐II. San Antonio, TX: Psychological Corporation; 1996. 28. Watson D, Clark L, Tellegen A. Development and validation of brief measures of positive and negative affect: The PANAS scales. J Pers Soc Psychol. 1988;54:1063–1070. 29. Stephens RS, Roffman RA, Curtin L. Comparison of extended versus brief treatments for marijuana use. J Consult Clin Psychol. 2000;68:898–908. 30. Heatherton TF, Kozlowski LT, Frecker RC, et al. The Fagerström test for nicotine dependence: A revision of the Fagerström Tolerance Questionnaire. Br J Addict. 1991;86:1119–1127. 31. Saunders JB, Aasland OG, Babor TF, et al. Development of the alcohol use disorders identification test (AUDIT): WHO collaborative project on early detection of persons with harmful alcohol consumption: II. Addiction. 1993;88:791–804. 32. Simons J, Correia CJ, Carey KB, et al. Validating a five‐factor marijuana motives measure: Relations with use, problems, and alcohol motives. J Counsel Psychol. 1998;45:265–273. 33. Heishman SJ, Singleton EG, Liguori A. Marijuana Craving Questionnaire: Development and initial validation of a self‐report instrument. Addiction. 2001;96:1023–1034.
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34. DiClemente CC, Hughes SO. Stages of change profiles in alcoholism treatment. J Subst Abuse. 1990;2:217–235. 35. Craig C, Marshall A, Sjostrom M, et al. International physical activity questionnaire: 12 country reliability and validity. Med Sci Sports Exerc. 2003;35:1381–1395. 36. Brown R, Abrantes A, Read J, et al. A pilot study of aerobic exercise as an adjunctive treatment for drug dependence. Ment Health Phys Activ. 2010;3:27–34. 37. Medina JL, Vujanovic AA, Smits JAJ, et al. Exercise and coping‐oriented alcohol use among a trauma‐exposed sample. Addict Behav. 2011;36: 274–277. 38. Hagstromer M, Oja P, Sjostrom M. The international physical activity questionnaire (IPAQ): A study of concurrent and construct validity. Public Health Nutr. 2006;9:755–762. 39. Sobell L, Sobell M. Timeline follow‐back: A technique for assessing self‐ reported ethanol consumption. In: Allen J, Litten RZ, eds. Measuring Alcohol Consumption: Psychosocial and Biological Methods. Totowa, NJ: Humana Press; 1992. pp. 41–72.
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40. Bonn‐Miller MO, Zvolensky MJ. An evaluation of the nature of marijuana use and its motives among young adult active users. Am J Addict. 2009;18:409–416. 41. Hjorthøj CR, Hjorthøj AR, Nordentoft M. Validity of timeline follow‐back for self‐reported use of cannabis and other illicit substances‐systematic review and meta‐analysis. Addict Behav. 2012;37:225–233. 42. Stephens R, Curtin L, Simpson E, et al. Testing the abstinence violation effect construct with marijuana cessation. Addict Behav. 1994;19: 23–32. 43. Smits JAJ, Bonn‐Miller MO, Tart CD, et al. Anxiety sensitivity as a mediator of the relationship between moderate‐intensity exercise and coping‐oriented marijuana use motives. Am J Addict. 2011;20:113–119. 44. Budney AJ, Hughes JR, Moore BA, et al. Marijuana abstinence effects in marijuana smokers maintained in their home environment. Arch Gen Psychiatry. 2001;58:917–924. 45. Bonn‐Miller MO, Zvolensky MJ, Moos RH. 12‐Step self‐help group participation as a predictor of marijuana abstinence. Addict Res Theory. 2011;19:76–84.
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Physical Activity and Cannabis Cessation Jessica G. Irons, PhD,1 Kimberly A. Babson, PhD,2,3 Cecilia L. Bergeria, BA,4 Marcel O. Bonn‐Miller, PhD2,5,6,7 1
Department of Psychology, James Madison University, Harrisonburg, Virginia Center for Innovation to Implementation, VA Palo Alto Health Care System, Menlo Park, California 3 Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Menlo Park, California 4 University of Vermont, Burlington, Vermont 5 National Center for PTSD, VA Palo Alto Health Care System, Menlo Park, California 6 Center of Excellence in Substance Abuse Treatment and Education, Philadelphia VA Medical Center, Philadelphia, Pennsylvania 7 Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 2
Background and Objectives: Based on recent empirical and theoretical work suggesting that physical activity (PA) activates many of the same physiological systems as cannabis, the present study sought to investigate the impact of PA level (ie, low [including none] vs. moderate/high) on a cannabis cessation attempt during the first 7 days post‐quit. Methods: The present study was a 2 time‐point prospective study of 84 cannabis dependent military veterans (3 female) who responded to study flyers, within a Veterans Affairs Medical Center, seeking individuals interested in engaging in a self‐guided cessation attempt. All study measures were self‐report. Results: Though no baseline differences between those with low and those with moderate/high levels of physical activity were observed, results revealed that participants who reported low levels of physical activity, versus moderate/high levels, were significantly more likely to report a cannabis lapse during the week following a quit attempt, particularly within the first 4 days of the cessation period. Further, individuals with low levels of PA were also more likely to report greater mean cannabis use during the first 4 days of the cessation period. Conclusions and Scientific Significance: Findings suggest that early interventions aimed at increasing physical activity may be useful among individuals with cannabis dependence who are engaged in a cessation attempt. (Am J Addict 2014;23:485–492)
Cannabis is the most widely used illicit drug in the United States1 and may lead to a variety of detrimental effects including, but not limited to, impairment while driving, carcinogenic exposure when smoked, and a decrease in motivation for activities that were once rewarding.2 Over time, chronic cannabis use leads to tolerance,3 with individuals who discontinue use after the development of tolerance experienc-
Received June 21, 2013; revised November 17, 2013; accepted November 23, 2013. Address correspondence to Dr. Irons, Department of Psychology, MSC 7704, James Madison University, Harrisonburg, VA 22807. E‐mail: [email protected].
ing symptoms of withdrawal, including cravings, irritability, sleep difficulties, and anxiety.4 Following, there has been consistent documentation of difficulty quitting among cannabis dependent individuals, regardless of motivation or treatment employed.5 Though current cultural and political trends push for its legalization, much remains to be understood about the drug and the full extent of cannabis’ effects, both detrimental and beneficial. Administration of the psychoactive component of cannabis (ie, delta‐9‐tetrahydrocannabinol; THC), activates the endocannabinoid system in the brain.6 With respect to endocannabinoid activation, cannabis use produces similar physiological events to physical activity (PA). For example, the “runner’s high,” previously thought to be primarily related to endorphins, has been linked to endocannabinoid activity, suggesting that endocannabinoids may play a role in the euphoric experience as a result of PA.7 Effects from the “runners high” include, but are not limited to, a reduction in anxiety and difficulties in estimating the passage of time.8,9 Endocannabinoids (unlike endorphins) are also effective at producing analgesic effects at central and peripheral nervous system locations and facilitating blood flow and respiration.10 To the extent that use of cannabis and engaging in PA lead to similar biological events it is possible that one behavior may function to substitute for the other, at least physiologically. Recent research suggests that engaging in intervention tactics that influence the endocannabinoid system for individuals with cannabis dependence may be effective.11 As discussed earlier, as aerobic PA has been shown to produce release of endocannabinoids (eg, anandamide), one strategy for activating the endocannabinoid system is engagement in PA. Recent studies have confirmed the activation of endogenous endocannabinoids as a result of moderate and high intensity levels of PA.12,13 Specifically, Sparling et al.12 found that participants who engaged in PA (ie, ran) for 50 minutes at moderate levels of intensity yielded elevated levels of 485
anandamide in blood samples compared to sedentary controls. These findings suggest that aerobic PA may be used as an intervention to influence cannabis use. Given that PA is associated with activity in the endocannabinoid system, it may lend itself well to abate withdrawal symptoms following a cessation attempt. Consistent with this notion, basic researchers have suggested that providing alternative ways of activating the endocannabinoid system may be a fruitful avenue for treating cannabis dependence.11 Recent studies suggest that greater participation in sports and PA is associated with lower levels of cannabis use, and conversely, decreased PA has been associated with greater use of cannabis.14–16 A recent study showed that a PA intervention involving a 1‐week adjustment period followed by ten 30‐ minute PA sessions (with target of 60% maximum heart rate) resulted in significant reductions in both cannabis craving and cannabis use during the intervention period and for the duration of the 2‐week follow‐up period.17 Once the PA intervention was removed, however, cannabis use returned toward pre‐treatment levels, suggesting that PA may have been a substitution for cannabis use, but only for the duration of the intervention. A similar line of work has suggested that PA reduces nicotine craving and improves nicotine cessation outcomes.18,19 While past research has found a relation between PA and cannabis use, the particulars of the influence of PA on cannabis use remains to be thoroughly investigated. The current study aims to examine the relation between PA levels and cannabis use following a self‐guided cannabis cessation attempt among dependent veterans. Veterans were a focus of this investigation because they represent a group that has evidenced marked increases in cannabis use disorder diagnoses over the past decade, and high rates of co‐occurring psychological disorders, with little to no sign of abatement.20 Based on recent work,17 it was hypothesized that individuals who reported a routine of moderate/high levels of PA immediately prior to a self‐guided quit attempt would have reduced rates of cannabis use, as well as reduced incidence of lapse (defined as any post‐cessation cannabis use21), as compared to those who engaged in PA at low levels (including those who engaged in zero PA). We chose to examine the association between PA and cannabis cessation outcomes among military veterans as recent evidence suggests a growing need for cannabis interventions among this population.20
METHOD Participants Participants were recruited via advertisements, targeting veterans interested in making a cannabis cessation attempt, which were placed throughout a VA medical center. The current sample included 84 cannabis dependent veterans (3 female; Mage ¼ 50.96 years, SD ¼ 10.07) from a larger parent study of 102 cannabis dependent veterans that examined factors impacting cannabis cessation success.22 The present sample was selected from the parent study as these individuals 486
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had complete data for all assessments over the first week of the cannabis cessation attempt. All study procedures were approved by the Institutional Review Boards (IRBs) of the VA Palo Alto Health Care System and Stanford University. Study inclusion criteria involved (1) being a U.S. veteran as assessed by the VA, (2) meeting diagnostic criteria for current cannabis dependence based on DSM‐5 criteria, (3) reporting a current level of motivation to quit of at least 5 on a 10 point scale (0 ¼ no interest in quitting to 10 ¼ definite interest in quitting), and (4) being interested in making a serious self‐ guided quit attempt. Individuals were excluded for the following reasons: (1) inability to provide informed, voluntary, written consent to participate, (2) having a significant decrease (of >25%) in amount of cannabis used per day during the previous month, and (3) currently pregnant or breastfeeding. Measures Baseline Characteristics AXIS‐I Diagnostic Status. Current Axis I diagnostic status (except posttraumatic stress disorder) was assessed via the Structured Clinical Interview‐Non‐Patient Version for DSM‐ IV (SCID I‐N/P23).1 The Clinician Administered PTSD Scale (CAPS25) is a well‐established semi‐structure interview that was used to determine diagnostic status of posttraumatic stress disorder (PTSD). Trained study staff conducted the SCID I‐N/ P and CAPS during the baseline assessment. All interviews were audio‐recorded and diagnoses were confirmed by the last author following a review of recorded interviews. Motivation to Quit Cannabis. Participants’ motivation to quit cannabis was assessed during baseline using an adapted version of the Contemplation Ladder (CL26). The CL is a visual analogue scale (VAS) comprised of 10 steps, each with a corresponding statement assessing motivation to quit cannabis. Items range from, 1 ¼ “I enjoy using marijuana and have decided not to quit using marijuana for my lifetime,” to 10 ¼ “I have quit using marijuana and I will never use again,” with 5 indicating “I often think about quitting using marijuana.” Depression Symptoms. The Beck Depression Inventory‐II (BDI‐II27) is a 21‐item measure that was administered at baseline to determine symptom severity of depression (Cronbach’s a ¼ .92). Positive and Negative Affect. The Positive and Negative Affect Schedule (PANAS28) is a 20‐item questionnaire that provides an index of general affect divided into two dimensions: positive and negative affect. The PANAS was delivered during the baseline assessment. Cronbach’s a ¼ .91 (positive affect), .93 (negative affect) for the current sample. Problematic Substance Use. Problematic cannabis use was assessed at baseline using the Marijuana Problems Scale (MPS29). This 19‐item scale is used to assess the negative social, occupational, physical, and personal consequences of cannabis use within the past 90 days. A total overall score was 1
The employed diagnostic criteria for cannabis dependence were consistent with the definition set forth in the DSM‐IV‐TR 24, with the addition of withdrawal, as proposed for DSM‐5 4. September–October 2014
used to index severity (Cronbach’s a ¼ .94). Problematic tobacco use was assessed using the 7‐item Fagerström Test for Nicotine Dependence (FTND30). A sum score was used to index overall severity (Cronbach’s a ¼ .75). Problematic alcohol use was assessed via the 10‐item Alcohol Use Disorders Identification test (AUDIT31). A total score was used as an overall index of severity (Cronbach’s a ¼ .93). Cannabis Motives. The Marijuana Motives Measure (MMM32) was used to assess motives for using cannabis. The MMM is a 25‐item measure used to assess 5 motives for use including: conformity (eg, “Because my friends pressure me to use marijuana,” expansion (eg, “To know myself better”), enhancement (eg, “Because it’s exciting”), coping (eg, “To forget my worries”), and social reasons (eg, “To be sociable”). In the current study Cronbach’s a ¼ .87 (conformity), .91 (expansion), .81 (enhancement), .83 (coping), and .87 (social). Cannabis Craving. Craving for cannabis was assessed using the 17‐item Marijuana Craving Questionnaire (MCQ33), which yields four factors: compulsivity (eg, unable to control cannabis use), emotionality (eg, use cannabis in anticipation of relieving emotional distress), expectancy (eg, anticipate a positive outcome), and purposefulness (eg, intention and planning to use). Within the current study Cronbach’s a ¼ .53 (compulsivity), .82 (emotionality), .76 (expectancy), and .75 (purposefulness). Readiness to change. Motivation and readiness to change cannabis use was assessed using the University of Rhode Island Change Assessment (URICA34). This 32‐item measure yields a sum score of overall level of readiness to change (Cronbach’s a ¼ .82). Primary Variables Physical Activity. The 4‐item International Physical Activity Questionnaire—Short Form (IPAQ‐SF35) was used to assess levels of physical activity. Participants are asked how many days/week and minutes/day they engaged in (1) high activity (ie, physically challenging activities that makes an individual breath much harder than normal); (2) moderate activity (ie, moderate level of physical activity that moderately increases breathing); (3) walking for at least 10‐minutes; and (4) sedentary activity (ie, sitting). Consistent with recommendations, data were cleaned of missing and out‐ of‐range values prior to scoring. Therefore, all individuals included in the current study had complete and reliable PA data. Metabolic equivalents (METS) minutes/week were calculated for walking, moderate, and high‐level activity. Categories of level of activity were then developed based on established scoring rules.35 For the purposes of the present study, moderate and high level activity were combined to make one group, based on existing literature demonstrating no clear differences between these two groups in terms of substance use outcomes.36,37 Those with low (including zero35) physical activity were within the second group. Validity studies indicated a high positive correlation with an activity monitor and the IPAQ data.38 IPAQ data were collected at baseline only. Irons et al.
Substance Use and Lapse. The Timeline Follow‐back interview (TLFB39) was administered at baseline to obtain frequency and quantity of cannabis, tobacco, and alcohol use over the course of the 90‐days prior to the cannabis quit attempt. The TLFB was also administered at one‐week post‐ quit to obtain substance use data for the week following the quit attempt. Quantity of cannabis used on each day was indexed by a graphical depiction that ranged from 0 to 8.40 Cannabis use information from the TLFB was used to determine lapse (defined as any use), and frequency/quantity of use at each of the 7 days post‐quit. The TLFB procedure has demonstrated good reliability and validity in past work across diverse samples,39 and has been demonstrated to be a reliable and valid indicator of cannabis use.41 Procedure Interested individuals contacted the research team and were provided with a description of the study over the phone and completed a preliminary phone‐based screening for initial eligibility. Those eligible scheduled a baseline appointment for one day prior to the day they were willing to make a serious self‐guided cannabis quit attempt. During this baseline appointment individuals completed informed consent procedures. Research staff then administered the SCID I‐ NP23 and CAPS25 to assess for psychopathology, with those remaining eligible then completing the TLFB39 and a battery of self‐report measures. Individuals were then compensated $75 for their time and instructed to make a serious cannabis quit attempt the next morning. Participants then returned for a follow‐up assessment 7 days following their quit day, when they again completed the TLFB39. At the end of the follow‐up appointment, participants were compensated $15 for their time. Data Analytic Approach Prior to the primary data analysis we examined the relations between PA and participant demographic and baseline characteristics via t‐tests (continuous variables) and chi‐square analyses (categorical variables), for descriptive purposes. Next, we sought to examine the relation between PA and both lapse and mean use of cannabis within each day of the first week of the quit attempt. In order to examine the impact of PA on lapse, we employed a Cox regression with time‐dependent covariates, as we expected PA would have a time‐dependent effect on lapse. Within this model, PA was entered as a time‐ dependent categorical variable. Lapse (yes/no) was entered as the censoring variable (1 indicating the event occurred), and covariates included baseline cannabis, alcohol, and tobacco use, and mean alcohol and tobacco use over the course of the quit week. In order to determine the impact of PA on lapse by each day of the quit attempt, we then conducted a series of logistic regressions. Here, lapse (yes/no) by each day (1 though 7) was entered within separate models (7 total analyses). PA (modeled categorically) was entered as the independent variable, and covariates included baseline cannabis, alcohol, and tobacco use, and mean alcohol and tobacco use for the days
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prior to and including the day of the lapse outcome (ie, Day 3 analyses included mean alcohol and tobacco use for Days 1–3). We examined the relation between PA (modeled categorically) and mean cannabis use within each day of the first week of the quit attempt using a series of t‐tests. Level of PA (low vs. moderate/ high) was entered as the between group variable with mean cannabis use by each of the first 7 days included as the outcome within 7 separate analyses. Alpha level was adjusted for multiple comparisons for all t‐tests using a Bonferroni correction (alpha ¼ .007).
ing in PA at low levels compared to moderate/high levels were not significantly different in terms of (a) problematic cannabis, alcohol, or tobacco use; (b) total cannabis, alcohol, and tobacco use during baseline; (c) daily use of cannabis, alcohol, and tobacco during baseline; (d) cannabis motives; (e) cannabis craving; (f) readiness for change; (g) or affect including positive and negative affect, and depression (see Table 2). In terms of rates of lapse during the first week of the quit attempt, 38.10% lapsed by Day 1, 46.40% by Day 2, 54.80% by Day 3, 57.10% by Day 4, 60.50% by Day 5, 61.90% by Day 6, and 65.50% lapsed by Day 7.
RESULTS
Physical Activity and Cannabis Use Outcomes: Lapse Results suggested that individuals engaging in low versus moderate/high levels of PA had greater risk for lapse over the course of the quit attempt after accounting for baseline cannabis, alcohol, and tobacco use, and mean alcohol and tobacco use over the course of the week, HR ¼ 4.42, 95% CI: 1.47–13.26. Logistic regressions suggested that individuals engaging in low versus moderate/high levels of PA had greater risk for lapse by Days 1–4, but not Days 5–7, after accounting for covariates (see Fig. 1 and Table 3).
Associations Between Physical Activity and Participant Characteristics On average, participants reported using cannabis regularly for 28.31 (SD ¼ 13.59) years. Table 1 provides an overview of participant characteristics in relation to demographic, substance use, and diagnostic status. In addition, we examined the association between PA and baseline characteristics in relation to substance use, readiness for change, and affect for descriptive purposes. Results demonstrated that those engag-
TABLE 1. Demographic information as a function of level of physical activity
Variable Age Gender (female) Employment Employed/retired Unemployed Ethnicity Caucasian African American Latino/Hispanic Asian/other Marital status Married Divorced Widowed Never married Education Some H.S. H.S. graduate Some college or more AXIS 1 diagnoses (current) Alcohol dependence Any depression Any anxiety PTSD
Low level M (SD) or N (%)
Moderate/high level M (SD) or N (%)
p‐Value
52.42 (6.36) 3 (11.1%)
50.27 (11.4%) 1 (1.75%)
.281 .060 .521
21 (77.8%) 6 (22.2%)
49 (85.9%) 8 (14.1%)
9 16 2 0
(33.3%) (59.3%) (7.4%) (0.0%)
23 14 10 10
(40.4%) (24.6%) (17.5%) (17.5%)
8 13 2 3
(30.8%) (50.0%) (7.7%) (11.5%)
11 23 2 18
(20.4%) (42.6%) (3.7%) (33.3%)
.536
.306
.549 1 (3.7%) 4 (14.8%) 22 (81.5%)
4 (7.0%) 10 (17.5%) 43 (75.5%)
6 4 10 12
13 11 19 20
(22.2%) (14.81%) (37.0%) (44.4%)
(22.8%) (19.3%) (33.3%) (35.1%)
.952 .616 .739 .410
M, mean; SD, standard deviation; H.S., high school; Axis 1 diagnoses were based on DSM‐IV criteria and were assessed via the Structured Clinical Interview for DSM‐IV (SCID‐NP; 23); any depression includes major depressive episode, major depressive disorder, and dysthymia; any anxiety includes panic disorder, generalized anxiety disorder, social anxiety disorder, obsessive compulsive disorder; PTSD, posttraumatic stress disorder.
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TABLE 2. Baseline characteristics as a function of level of physical activity
Variable Problematic substance use Cannabis Tobacco Alcohol Total use during 90 d of baseline Cannabis Tobacco Alcohol Amount of use/d of baseline Cannabis Tobacco Alcohol Cannabis motives Enhancement Social Conformity Expansion Coping Cannabis craving Compulsive Emotional Expectancy Purposeful Readiness to change Readiness for change Affect Positive Negative Depression
Low level, M (SD) or N (%)
Moderate/high level, M (SD) or N (%)
Range
p‐Value
7.99 (9.16) 2.94 (1.39) 17.64 (13.37)
10.00 (9.41) 2.80 (1.09) 12.80 (11.71)
0–37 0–5 0–45
.669 .702 .105
529.37 (164.33) 670.85 (734.58) 256.78 (417.15)
476.52 (198.77) 486.66 (718.19) 173.00 (487.13)
135–720 0–2720 0–2927
.235 .280 .445
6.02 (1.71) 12.07 (7.47) 6.00 (5.36)
6.03 (2.03) 10.68 (8.24) 4.68 (6.81)
1–8 0–30 0–34
.963 .566 .473
3.98 3.38 1.67 2.63 3.47
(0.78) (1.27) (1.03) (1.33) (1.12)
3.49 2.91 1.76 2.56 3.21
(1.09) (1.09) (0.92) (1.17) (1.25)
1–5 1–5 1–5 1–5 1–5
.038 .079 .689 .812 .342
9.07 11.48 12.96 13.09
(4.76) (5.94) (5.52) (5.61)
8.28 10.56 11.47 11.92
(4.34) (5.19) (5.37) (5.24)
3–21 3–21 3–21 3–21
.455 .473 .244 .353
9.22 (2.19)
8.57 (1.80)
0–13
.150
32.35 (10.45) 21.73 (9.18) 17.78 (12.34)
32.12 (8.41) 22.98 (10.22) 17.71 (12.27)
0–50 0–50 0–51
.919 .596 .980
Problematic substance use: cannabis (Marijuana Problems Scale), tobacco (Fagerstrom Test for Nicotine Dependence), Alcohol (Alcohol Use Disorder Identification Test; Total use and amount of use per day for alcohol, tobacco, and cannabis were determined through the Timeline Follow Back; Cannabis motives was assessed via the Marijuana Motives Scale; Cannabis craving was assessed via the Marijuana Craving Scale; Readiness to change was assessed through the University of Rhode Island Change Assessment; Positive and negative affect were assessed through the Positive and Negative Affect Schedule; Depression was assessed via the Beck Depression Inventory.
Physical Activity and Cannabis Use Outcomes: Mean Use A series of t‐tests demonstrated that PA (low levels versus moderate/high levels) was associated with mean cannabis use for Days 1–4 of the quit attempt. Specifically, for Days 1–4, individuals with low levels of PA had greater mean cannabis use compared to those engaging in PA at moderate/high levels (see Table 3).
DISCUSSION The current study demonstrates that cannabis dependent veterans who self‐reported engaging in PA at moderate/high levels exhibit lower rates of lapse during the first 4 days following a self‐guided quit attempt, as compared to those who reported low levels or not engaging in PA. Furthermore, Irons et al.
participants who reported moderate/high PA had lower cumulative mean cannabis use on Days 1–4 post‐quit. Baseline characteristics (eg, substance use, affect) were similar for participants who reported moderate/high levels of PA and those who reported low levels or no PA. These data support the notion that PA may have advantageous effects with respect to cannabis use and lapse and thus may be a potential early intervention strategy for cannabis users. Incidence of cannabis lapse is predictive of subsequent relapse such that early intervention is critical.42 Taken together, the current study data and previous work, suggesting that a PA intervention may serve to reduce cannabis use,17 provide compelling evidence of the putative benefits of engaging in moderate/high PA as an intervention for individuals with cannabis dependence. Further studies are necessary to fully elucidate the conditions under which PA may improve cannabis use rates (eg, as a stand‐alone intervention or
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symptoms peak by the third day following a cessation attempt.44 Indeed, it is possible that PA is most relevant during periods of heightened withdrawal, while other factors (eg, social support45) may be more important for long‐term quit success. Future studies might specifically consider the role of PA in reducing cannabis use as a function of abating or delaying withdrawal symptoms. The present study findings are consistent with previous work examining the relation between PA and cannabis use; however, there are several limitations to consider. Though PA may act as a putative substitute for cannabis use, other possibilities remain unexamined. For example, PA could function as a complement (additively or multiplicatively) to the cannabis high, such that use is maintained more readily. It is also possible that PA and cannabis use have no measureable effects on one another (and previous studies represent Type I error or results confounded by extraneous influences). Further, there may be unidentified mechanisms by which PA may influence substance use generally, and not cannabis specifically. Additional limitations related to sample characteristics must be considered. Our sample consisted of heavy substance using veterans interested in engaging in a self‐guided cessation attempt. Our homogenous sample provides great insight about a vulnerable population with respect to substance dependence; however, it remains to be seen if our findings will generalize to other populations. For example, while our gender distribution is consistent with the veteran population, additional research should examine findings among more gender diverse samples. Additionally, our PA data do not allow for insight into potential relative benefits of different types of activity (eg, running relative to walking or weight lifting) such that future research might consider additional measures related to physical activities. Further, our use of self‐report to gather data related to PA poses a potential limitation and future research might consider objective measures of PA. In addition, our comparisons are quasi‐experimental in nature and our study was of a short duration such that causal inference is further limited. Understanding of the effects of PA on cannabis use will
FIGURE 1. The percent of individuals lapsing by each day of the first week of a cannabis quit attempt as a function of level of physical activity (low vs. moderate/high). Stars indicate significant differences at p < .05.
as an adjunct to other treatment efforts) as well as for whom such an intervention might be most effective (eg, among those with anxiety or coping‐oriented cannabis use43). In addition, studies will need to examine how best to implement a PA intervention (eg, intensity, frequency, and/or duration of time spent engaged in PA; cardiovascular versus anaerobic work) to maximize benefit and minimize harm (eg, protect previously sedentary individuals from injury). It is unclear why differences in lapse rates and mean use between those who reported moderate/high levels of PA and those who reported low levels or no PA occurred only within the first 4 days following a quit attempt. At least 2 possible explanations warrant further examination. First, as PAwas only measured immediately pre‐cessation, it is possible that as time progressed, participant PA level changed, thus rendering baseline levels progressively less predictive over time. Alternatively, this pattern of findings may be related to the experience of withdrawal symptoms; most salient withdrawal
TABLE 3. Mean use and lapse per day as a function of low and high levels of physical activity
Day(s) 1 1–2 1–3 1–4 1–5 1–6 1–7
Low PA
Moderate/high PA
M (SD)
M (SD)
2.96 2.98 2.97 2.88 2.78 2.79 2.79
(3.05) (3.06) (2.99) (2.95) (2.88) (2.82) (2.80)
1.14 1.21 1.32 1.35 1.41 1.42 1.42
(2.08) (1.83) (1.81) (1.82) (1.74) (1.73) (1.68)
Mean use
Lapse
t
p‐Value
Day
OR
95% CI
p‐Value
3.20 3.28 3.12 2.91 2.70 2.74 2.70
.002 .001 .002 .005 .008 .007 .008
1 2 3 4 5 6 7
.14 .18 .21 .02 .31 .33 .42
.04–.46 .05–.59 .06–.67 .07–.77 .09–1.02 .11–1.04 .13–1.36
.001 .005 .009 .016 .054 .058 .149
Low PA, low level of physical activity; Moderate/high PA, moderate or high level of physical activity. Statistically significant at p < .05. Statistically significant at p < .007, accounting for Bonferroni correction.
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benefit from a randomized controlled trial including baseline, intervention, and follow‐up measures of both cannabis use and PA. Together, the present study served as the first prospective empirical investigation of the impact of PA on cannabis cessation outcomes among military veterans. The capacity of PA to delay or prevent withdrawal symptoms upon cannabis cessation may serve as a viable complement to existing intervention strategies, if not as a standalone intervention for dependent use. Further, given the increasing rates of cannabis use disorder diagnoses among veterans,20 the use of PA interventions as complements to existing cannabis use disorder treatments within the Veterans Administration may be warranted. Additional experimental studies examining the effects of PA on cannabis use are necessary to confirm (or disconfirm) these ideas as well as add to our understanding of effects over time and across populations, contexts, and differing levels of cannabis use. This work was supported, in part, by A VA Clinical Science Research and Development (CSR&D) Career Development Award—2 (Bonn‐Miller), and VA Health Services Research and Development Service funds (Babson). The expressed views do not necessarily represent those of the Department of Veterans Affairs. Declaration of Interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this paper.
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