In people with chronic noncancer pain, cannabinoid drugs reduce pain by a small amount but increase adverse events

Stockings E, Campbell G, Hall WD, et al. Cannabis and cannabinoids for the treatment of people with chronic noncancer pain conditions: a systematic review and meta-analysis of controlled and observational studies. Pain. 2018;159(10):1932-54.

Review question

In people with chronic noncancer pain (CNCP), do cannabinoid drugs relieve pain?

Background

Chronic pain that is unrelated to cancer is common. It includes neuropathic pain (pain caused by damage to the nervous system), fibromyalgia, arthritis-related pain, and other types of noncancer pain. There are many treatments for CNCP. This review looks at whether a specific class of drugs, cannabinoids, can relieve CNCP.

Cannabinoids come from the cannabis plant or can be human-made. They affect different parts of the body, including the central nervous system and immune system, and may reduce pain and inflammation.

How the review was done

The researchers did a systematic review of studies available up to July 2017. They found 104 studies evaluating cannabinoids, including 47 randomized controlled trials (RCTs). The RCTs included 4,271 people with an average age of 39 to 67 years.

The key features of the RCTs were:

• most people had neuropathic pain or multiple sclerosis–related CNCP;
• cannabinoids included Cannabis sativa, dronabinol, nabilone, nabiximol, and cannabis extracts;
• most cannabinoids were taken by mouth or sprayed under the tongue; some were smoked or inhaled as a vapour;
• most cannabinoids were given with other pain-relieving drugs and compared with placebo; and
• most people used cannabinoids for 16 weeks or less.

What the researchers found

Most of the evidence was of moderate strength (moderate confidence that additional studies would show the same results).

Compared with placebo, cannabinoids:

• were better at reducing pain by at least 30%;
• were not better at reducing pain by at least 50%;
• reduced pain intensity by about 3 more points out of 100; and
• increased adverse events overall.

Adverse events that were more frequent with cannabinoids included dizziness, depressed mood, negative cognitive or attention effects, nausea, drowsiness, confusion and disorientation, intoxication, change in appetite, and dry mouth. Evidence for individual adverse effects was low or very low quality (additional studies may show different results).

Conclusion

In people with chronic noncancer pain, cannabinoid drugs reduce pain by a small amount but increase adverse events.

Cannabinoids vs placebo in people with chronic noncancer pain*

*Based on results of randomized controlled trials. Evidence was of moderate strength (moderate confidence that additional studies would show the same results).

†The event rate in the cannabinoids group was weighted. This means it may be a little different than you would expect if you just divided number of people who had an event with the number of people who were treated.

‡Although the rates for the 2 groups look a little different, the differences were not statistically significant. This means that the differences could simply be due to chance rather than due to different treatments.