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Using Cannabis to Treat PTSD Isn’t Yet Supported by High-quality Evidence

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The use of cannabis to treat the symptoms of post-traumatic stress disorder (PTSD) is on the rise, but this increase isn’t yet supported by the evidence, suggests a new study from University College London (UCL)

"There has been a recent surge of interest in the use of cannabinoids to treat PTSD, particularly from military veterans, many of whom are already self-medicating or obtaining prescriptions in some American states," said Chandni Hindocha, a researcher at UCL’s Clinical Psychopharmacology Unit and the study’s lead author.

The paper, published in the Journal of Dual Diagnosis concluded that cannabis may potentially help reduce the sleep disturbances that are a hallmark of PTSD, but that additional research is required before these drugs should be used in routine clinical prescription.

PTSD, a condition that affects up to one percent of the general population, involves the re-experiencing of traumatic events. This manifests as disturbing memories and nightmares and is characterized by hyper-reactivity – being constantly vigilant to potential threats – and insomnia. Classical treatment approaches for PTSD include talking therapies, such as  trauma-focused cognitive behavioral therapy (T-F CBT). These are not always effective and are hard to access. In the 33 US states where medical cannabis is legal, prescriptions for PTSD treatment have become more common.

Why should cannabis help with PTSD?

The biological basis of cannabis’s beneficial effects for PTSD patients hinges on the cannabinoids, a class of molecule that includes the cannabis metabolites tetrahydrocannabinol (THC) and cannabidiol (CBD) as well as endogenous molecules in the human brain.

Hindocha’s team conducted a systematic review of every study where a patient had been recorded using cannabinoids to fight the symptoms of PTSD. This list stretched to just 10 studies, which were variable in method and quality.

Some studies examined the use of cannabinoid oils or supplements, some looked at the use of the synthetic cannabinoid nabilone, whilst others looked at old fashioned cannabis smoking as a treatment.

A lack of quality

Each study analyzed was determined to be of a low quality due to limitations such as:

  • small sample size
  • lack of control group
  • short follow-up periods
  • lack of reporting of other medicine use
  • retrospective study design

Just one study was of the gold standard randomized controlled trial format but is still limited by small sample size and its lack of longitudinal insight. 

The study’s senior author, Michael Bloomfield summed up the findings: "Based on the evidence, we cannot yet make any clinical recommendations about using cannabinoids to treat PTSD. Current prescribing of cannabinoids for PTSD is not backed up by high quality evidence, but the findings certainly highlight the need for more research, particularly long-term clinical trials.”

Promise in fighting insomnia

The studies did show some promise, as cannabis use appeared to cut the insomnia and nightmares associated with PTSD, but there were clearly many unanswered questions surrounding safety and the potential long-term effects of use. The risk of psychosis, which is associated with high levels of cannabis use, was a further factor that needs to be investigated.

Bloomfield added, “Many of these studies have been conducted in military veterans, but we also need to be looking at other groups, as PTSD can vary depending on the nature of the trauma so different approaches may benefit different groups.”

Hindocha touched on the difficulties of developing medical trials of high quality involving the drug. He said,: "Unfortunately, medicinal uses of cannabis have historically been difficult to study due to legal restrictions, so it could take a long time before there is enough evidence to support clinical recommendations. New approaches are needed to make the most of existing evidence in the meantime."

Reference: Hindocha, C., Cousijn, J., Rall, M., & Bloomfield, M. A. P. (2019). The Effectiveness of Cannabinoids in the Treatment of Posttraumatic Stress Disorder (PTSD): A Systematic Review. Journal of Dual Diagnosis, 0(0), 1–20. https://doi.org/10.1080/15504263.2019.1652380