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Publication Briefs

Systematic Review: Benefits and Harms of Cannabis for PTSD

Cannabis use has become more common in the U.S., with the number of persons reporting past-year use nearly doubling between 2001 and 2013 to 1 in 10 adults. Many states list PTSD as an indication for cannabis use, and more than one-third of patients seeking cannabis for medical purposes cite PTSD as the primary reason for the request. However, little comprehensive and critically appraised information is available about the benefits and harms of cannabis use for treating PTSD. This systematic review sought to assess the effectiveness of plant-based cannabis use in patients with PTSD -- and to identify ongoing studies in this area. Investigators with HSR&D's Evidence-based Synthesis Program Center located in Portland, OR searched multiple data sources (i.e., MEDLINE, Embase, PubMed) and grey literature (outside traditional publishing channels) sources from database inception through March 2017. After reviewing more than 13,700 titles and abstracts, investigators identified 2 systematic reviews and 3 primary studies that were relevant to their analysis.


  • Evidence is insufficient to draw conclusions about the benefits and harms of plant-based cannabis preparations in patients with PTSD, but ongoing studies may soon provide important results.
  • One large observational study examined 4-month outcomes for 2,276 Veterans in VA intensive PTSD programs from 1992 to 2011. Adjusted analyses show that continuing cannabis users and starters (no cannabis use before study) had worse PTSD symptoms than never-users and stoppers (used cannabis before but not after study began), although the absolute differences were small.
  • Two randomized controlled trials (RCTs) were recently initiated to evaluate the benefits and harms of cannabis therapy for PTSD. One study, conducted by the Colorado Department of Public Health and Environment, will assess the effects of four different types of cannabis on PTSD symptoms in Veterans (expected completion date is 2019). Another study will examine the effects of different amounts of cannabis in comparing PSTD, mental health, and physical health outcomes.


  • Clinicians will need to engage in evidence-informed discussions with patients who have PTSD and choose to use or request cannabis. Potential mental-health related harms may exist that are particularly relevant for patients with PTSD. For example, the investigators' full evidence synthesis report and another article show low-to-moderate strength evidence that cannabis use is associated with an increased risk for psychotic symptoms, psychosis, and mania. And in active users, cannabis use also can result in short-term cognitive dysfunction.


  • The current body of literature is limited by small sample sizes, lack of adjustment for important potential confounders, cross-sectional study designs, and a paucity of studies with non-cannabis-using control groups.

This review was funded by VA HSR&D's Quality Enhancement Research Initiative (QUERI) Evidence-based Synthesis Program (ESP). Drs. O'Neil, Nugent, and Morasco are part of QUERI's Evidence-Based Synthesis Program Center, Portland, OR.

PubMed Logo O’Neil M, Nugent S, Morasco B, et al. Benefits and Harms of Plant-Based Cannabis for Post-traumatic Stress Disorder: Systematic Review. Annals of Internal Medicine. September 5, 2017;167(5):332-340.

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What are HSR Publication Briefs?

HSR requires notification by HSR-funded investigators about all articles accepted for publication. These journal articles are reviewed by HSR and publication briefs or summaries are written for a select number of articles that are then forwarded to VHA Central Office leadership to keep them informed about important findings or information. Articles to be summarized are selected by HSR based on timeliness of the findings, interest of leadership, or potential impact on the organization. Publication briefs are written for only a small number of HSR published articles. Visit the HSR citations database for a complete listing of HSR articles and presentations.

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