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Major Study on Cannabis and PTSD Less Conclusive Than Hoped

Post-traumatic stress disorder (PTSD) is a condition that follows in the wake of a deeply traumatic event. Symptoms may manifest shortly after the event or they may develop months or even years later. Symptoms include hypervigilance, irritability, troubled sleep, and intrusive thoughts, among others. In addition to these symptoms, those who suffer from PTSD have high rates of psychiatric comorbidities like anxiety and depression. Non-related disabilities are also common, particularly among veterans.

For decades, many who suffer from PTSD have used cannabis to self-medicate and to manage symptoms, claiming that it reduces anxiety and stress while improving sleep and mood. Many activists have cited this kind of anecdotal evidence as proof of its efficacy, but well-designed studies using high-quality flower cannabis samples have been lacking. Samples from the federal government are infamous for being less than second-rate and pale in comparison to the kind of cannabis found in dispensaries. Meanwhile, other studies have used isolated cannabinoids. In either case, they were not reflective of the products actually being used by patients.

This was a major concern for Arizona-based physician Sue Sisley, M.D., who has performed pioneering research into PTSD and cannabis, and has spent around a decade fighting to obtain high-quality cannabis for her studies. Because she was finally able to obtain quality samples (including one with a high concentration of tetrahydrocannabinol (THC), one with a high concentration of cannabinol (CBD), and one with a THC to CBD ratio of 1:1), many within the world of cannabis research have eagerly awaiting the results of her most recent study. This week she published her paper documenting the results of her randomized, double-blind, placebo-controlled, crossover trial in PLOS ONE.

The conclusions are, unfortunately, not as strong as many had hoped. On the one hand, the use of cannabis was well tolerated and there was no evidence that symptoms became exacerbated during the trial. On the other, all participants, including those who received placebo, saw similar within-subject reductions in total CAPS-5 (Clinician-Administered PTSD Scale for DSM-5) Total Severity scores between baseline and the end of the three-week study. In other words, the study failed to find a significant group difference between placebo and the three samples of high-quality cannabis.

While it is far from conclusive evidence against the use of cannabis to treat PTSD, the study does not offer the level of proof of efficacy for which many cannabis advocates were hoping. Future studies that examine the use of cannabis to treat symptoms associated with PTSD will likely build upon the lessons learned from this trial, and will hopefully provide more definitive results.

PLOS ONE has more.

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