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What we know
Use of cannabis products among American adults has risen substantially over the past two decades (Hasin et al., 2015), and Americans increasingly perceive cannabis use to be safe (Compton et al., 2016). Along with these changes, states have passed laws allowing dispensaries to sell cannabis commercially, and enabling individuals with a variety of physical and mental health conditions to access cannabis legally. In some states, veterans’ groups have lobbied successfully for posttraumatic stress disorder (PTSD) to be added as a qualifying condition for accessing legal cannabis (Boehnke et al., 2019), and recent national surveys have found that more than 1 in 4 veterans with PTSD report recent cannabis use (Hill et al., 2021). 
What we wanted to know
Despite these changes, the impact of cannabis use on PTSD symptoms is poorly understood, and even less is known about how cannabis use relates to other aspects of distress and functioning for individuals with PTSD. These are important considerations given that individuals with PTSD symptoms often also experience depression, anxiety, and suicidal ideation (Wisco et al., 2014); report difficulties with psychosocial, cognitive, emotional, and physical functioning (Bovin et al., 2018; McCarthy et al., 2019); and attempt to avoid trauma reminders in order to reduce their PTSD symptoms (Palmisano et al., 2022). These problems, in turn, may interfere with engagement in trauma-focused treatments that are known to be effective (Maguen et al., 2021), but require interacting with trauma memories and reminders. 
Given conflicting messages about whether cannabis might be harmful or helpful for people with PTSD, clinicians may feel confused about how to address use of cannabis products with their patients. For veterans served within the Veterans Health Administration (VHA), the topic can feel even trickier, as VHA policy prohibits recommending medical cannabis to patients. However, giving patients accurate and timely information about cannabis and PTSD may help inform their decisions about use of cannabis products. To help provide clinicians with such information, we sought to characterize how cannabis use relates to important clinical indicators in veterans with PTSD symptoms. 
Specifically, we analyzed data from a large, nationally representative sample of U.S. military veterans to examine associations of cannabis use with psychiatric comorbidities, treatment engagement, measures of daily functioning, and strategies for coping with PTSD symptoms among trauma-exposed veterans with clinically significant levels of PTSD symptoms.
What we learned
Compared with veterans who either did not use cannabis or used it infrequently, veterans who used cannabis more than once a week were nearly twice as likely to screen positive for co-occurring depression, anxiety, and suicidal ideation; had worse cognitive functioning; and were nearly two times more likely to rely primarily on avoidance-based coping strategies to manage their PTSD symptoms. Despite this more severe clinical presentation, however, veterans who used cannabis frequently were no more likely than other veterans with PTSD symptoms to be engaged in mental health treatment, including psychotherapy and medication. 
It is possible that the greater reliance on avoidance coping strategies among veterans with frequent cannabis use might make them less likely to pursue and engage in PTSD treatment. Specifically, we found that veterans who used cannabis more than weekly were 2 to 6 times more likely than other veterans with PTSD symptoms to report substance use and disengagement (defined here as “giving up”) as one of their top three coping strategies for dealing with PTSD symptoms. Given that motivation is important for mental health treatment (Mütze et al., 2021), these results highlight the importance of identifying strategies to help veterans with PTSD and frequent cannabis use to engage in evidence-based treatments for PTSD and co-occurring disorders. 
What’s next 
Results of this study provide clinicians with information for discussions about cannabis use with their patients. Because frequent cannabis use was related to a range of problems indicating more severe distress and impairment, it may be helpful for clinicians to screen for problematic cannabis use and talk with their patients about strategies for reducing risky cannabis use (Fischer et al., 2017). 
However, because we asked veterans about their cannabis use and mental health and functioning at one point in time, it is unclear whether cannabis use is responsible for the differences we observed between veterans who did and did not use cannabis frequently, and many questions remain about the role of cannabis use in the progression and treatment of trauma-related problems. Further research is needed to determine whether cannabis use predicts later exacerbation of mental health and functional problems in veterans with PTSD or vice versa, and randomized controlled studies can clarify how reducing cannabis use might impact PTSD treatment outcomes.

Target Article 

Hill, M. L., Loflin, M., Nichter, B., Na, P. J., Herzog, S., Norman, S. B., & Pietrzak, R. H. (2022). Cannabis use among U.S. military veterans with subthreshold or threshold posttraumatic stress disorder: Psychiatric comorbidities, functioning, and strategies for coping with posttraumatic stress symptomsJournal of Traumatic Stress.

Discussion Questions

  • Does beginning or increasing cannabis use lead to exacerbation of co-occurring psychiatric disorders, functional difficulties, and avoidance coping in people with PTSD?
  • Does quitting versus continuing cannabis use improve treatment outcomes for veterans with PTSD? 
  • How can we modify or supplement existing PTSD treatments like Prolonged Exposure and Cognitive Processing Therapy to increase treatment engagement and retention among veterans using cannabis? 

About the Authors

Melanie L. Hill, Ph.D., is a postdoctoral fellow in the Interprofessional Advanced Fellowship in Addiction Treatment at VA San Diego Healthcare System and a Visiting Scholar at the University of California, San Diego School of Medicine.  
Sonya B. Norman, Ph.D., is Director of the PTSD Consultation Program for the National Center for PTSD and a Professor in the Psychiatry Department in the University of California, San Diego School of Medicine.
Robert H. Pietrzak, Ph.D., M.P.H. is Director of the Translational Psychiatric Epidemiology Laboratory of the Clinical Neurosciences Division of the National Center for PTSD, Professor of Psychiatry at Yale School of Medicine, Professor of Public Health (Social and Behavioral Sciences) at Yale School of Public Health, and Adjunct Professor of Psychiatry and Environmental Medicine and Public Health at Icahn School of Medicine at Mount Sinai.

References Cited

Boehnke, K. F., Gangopadhyay, S., Clauw, D. J., & Haffajee, R. L. (2019). Qualifying conditions of medical cannabis license holders in the United States. Health Affairs, 38(2), 295-302. http://dx.doi.org/10.1377/hlthaff.2018.05266
Compton, W. M., Han, B., Jones, C. M., Blanco, C., & Hughes, A. (2016). Marijuana use and use disorders in adults in the USA, 2002–14: analysis of annual cross-sectional surveys. The Lancet Psychiatry, 3(10), 954-964. http://dx.doi.org/10.1016/ S2215-0366(16)30208-5
Fischer, B., Russell, C., Sabioni, P., Van Den Brink, W., Le Foll, B., Hall, W., Rehm, J., & Room, R. (2017). Lower-risk cannabis use guidelines: a comprehensive update of evidence and recommendations. American Journal of Public Health, 107(8), e1-e12. https://doi.org/10.2105/AJPH.2017.303818
Hasin, D. S., Saha, T. D., Kerridge, B. T., Goldstein, R. B., Chou, S. P., Zhang, H., Jung, J., Pickering, R. P., Ruan, W. J., Smith, S. M., Huang, B., & Grant, B. F. (2015). Prevalence of marijuana use disorders in the United States between 2001-2002 and 2012-2013. JAMA Psychiatry, 72(12), 1235-1242. http://dx.doi.org/10.1001/jamapsychiatry.2015.1858
Hill, M. L., Loflin, M., Nichter, B., Norman, S. B., & Pietrzak, R. H. (2021). Prevalence of cannabis use, disorder, and medical card possession in US military veterans: Results from the 2019–2020 National Health and Resilience in Veterans Study. Addictive Behaviors, 120, 106963. https://doi.org/10.1016/j.addbeh.2021.106963
Maguen, S., Madden, E., Holder, N., Li, Y., Seal, K. H., Neylan, T. C., Lujan, C., Patterson, O. V., DuVall, S. L., & Shiner, B. (2021). Effectiveness and comparative effectiveness of evidence-based psychotherapies for posttraumatic stress disorder in clinical practice. Psychological Medicine, 1-10. https://doi.org/10.1017/S0033291721001628
Mütze, K., Witthöft, M., Lutz, W., & Bräscher, A. K. (2021). Matching research and practice: Prediction of individual patient progress and dropout risk for basic routine outcome monitoring. Psychotherapy Research, 1-14. https://doi.org/10.1080/10503307.2021.1930244

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