More Evidence Needed to Support Medical Marijuana for PTSD, Chronic Pain


Low-strength evidence shows cannabis may alleviate neuropathic pain, but evidence of benefits in other populations was insufficient.

Researchers continue to search for evidence regarding the use of cannabis for medicinal purposes.

In 2 reviews recently published in the Annals of Internal Medicine, researchers analyzed ongoing studies aimed at plant-based cannabis’ medicinal benefits, including use in chronic pain and posttraumatic stress disorder (PTSD).

One of the studies demonstrated low-strength evidence that cannabis may alleviate neuropathic pain, although evidence of benefits in other pain populations was insufficient.1 Increased risk for motor vehicle accidents, psychotic symptoms, and short-term cognitive impairment were noted as possible harms associated with cannabis use in this population. Evidence regarding long-term physical harms in heavy cannabis users or in older populations was insufficient.

Additionally, the researchers noted that limited evidence suggested that cannabis is associated with an increased risk for adverse mental health effects. Although limited evidence was found, the researchers noted that further research is needed to clarify the effects of cannabis, especially since a recent report from the National Academies of Sciences, Engineering, and Medicine cited chronic pain relief as a therapeutic benefit of cannabis.

In another review, investigators aimed to determine the benefits and harms of plant-based cannabis preparations in treating adults with PTSD.2 In the systematic reviews identified, evidence was insufficient to draw conclusions about the benefits and harms. However, in the observational studies, cannabis use did not appear to reduce PTSD symptoms compared with nonuse. The researchers indicated that findings from randomized controlled trials are needed to determine the extent of cannabis’ effect on improving PTSD symptoms and whether there are harms associated with use in patients with PTSD.

Several ongoing studies examining the outcomes of cannabis use in patients with PTSD are expected to be completed within the next few years.

Several past studies have looked to identify potential health benefits of cannabis, and some have indicated therapeutic value in therapeutic areas including opioid use disorders and epilepsy.


  • Nugent SM, Morasco BJ, O’Neil ME, et al. The effects of cannabis among adults with chronic pain and an overview of general harms: a systematic review. Ann Intern Med. 2017. doi: 10.7326/M17-0155
  • O’Neil ME, Nugent SM, Morasco BJ, et al. Benefits and harms of plant-based cannabis for posttraumatic stress disorder: a systematic review. Ann Intern Med. 2017. doi: 10.7326/M17-0477

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