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 Sep 5;167(5):319-331. doi: 10.7326/M17-0155. Epub 2017 Aug 15.
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Background: Cannabis is increasingly available for the treatment of chronic pain, yet its efficacy remains uncertain.

Purpose: To review the benefits of plant-based cannabis preparations for treating chronic pain in adults and the harms of cannabis use in chronic pain and general adult populations.

Data Sources: MEDLINE, Cochrane Database of Systematic Reviews, and several other sources from database inception to March 2017.

Study Selection: Intervention trials and observational studies, published in English, involving adults using plant-based cannabis preparations that reported pain, quality of life, or adverse effect outcomes.

Data Extraction: Two investigators independently abstracted study characteristics and assessed study quality, and the investigator group graded the overall strength of evidence using standard criteria.

Data Synthesis: From 27 chronic pain trials, there is low-strength evidence that cannabis alleviates neuropathic pain but insufficient evidence in other pain populations. According to 11 systematic reviews and 32 primary studies, harms in general population studies include increased risk for motor vehicle accidents, psychotic symptoms, and short-term cognitive impairment. Although adverse pulmonary effects were not seen in younger populations, evidence on most other long-term physical harms, in heavy or long-term cannabis users, or in older populations is insufficient.

Limitation: Few methodologically rigorous trials; the cannabis formulations studied may not reflect commercially available products; and limited applicability to older, chronically ill populations and patients who use cannabis heavily.

Conclusion: Limited evidence suggests that cannabis may alleviate neuropathic pain in some patients, but insufficient evidence exists for other types of chronic pain. Among general populations, limited evidence suggests that cannabis is associated with an increased risk for adverse mental health effects.

Primary Funding Source: U.S. Department of Veterans Affairs. (PROSPERO: CRD42016033623).

Comments from MORE raters

Physician rater

This is a super topical issue as this intervention is promoted as one thing to try and ease the opioid crisis. It's something primary care physicians need to know about.

Physician rater

Medical cannabis has been in the news recently with clinicians castigated for not prescribing it enough; so, it is important to have this summary of the evidence showing too few trials that are not rigorous enough and are too short. We urgently need more good RCTs of long duration.

Physician rater

Because of social considerations, it is difficult to separate science and superstition in the use of cannabis. Neuropathy is not necessarily the best condition for testing because it is very difficult to quantify the severity of the disorder.

Physician rater

Very interesting to see what a compilation of the limited literature shows. There are some potential good and harm to weigh, with lots of limitations.

Physician rater

Not definitive by any means, so the conclusions are not practice-changing.

Physician rater

This is another systematic review of medicinal cannabis use, essentially showing little evidence to guide clinical practice. We are asking for more trials.

Physician rater

Good review of existing literature on the use of cannabis and its POSSIBLE effect on pain. The data reviewed are quite mixed and don`t tell us much about the potential long-term effects. I doubt anyone is recommending this for short-term pain, so we are left with a disconnect between the literature showing poor-quality evidence for an effect long term and some bad long-term diseases that might potentially benefit.
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