Cannabis and Chronic Pain
Cannabis and Chronic Pain
By Benjamin J. Morasco, PhD and Devan Kansagara, MD MCR
Chronic pain is common and often treatment resistant. Pain is also the most frequently cited indication for medical cannabis use.
Efficacy of cannabis for chronic pain
The data presented here are from a living systematic review originally published in December 2020 and updated quarterly.
- An oromucosal spray with comparable amounts of THC and CBD is the most studied formulation. It was associated with a small reduction in pain severity, a small improvement in functional status, and a large increase in dizziness and sedation (low to moderate strength evidence).
- On average, participants used about 25 mg THC per day in these studies.
- Synthetic formulations of THC were associated with moderate reductions in pain, a large increase in dizziness, and a moderate increase in sedation (low to moderate strength evidence)
- The average THC dose ranged from 2 mg to 25 mg per day in these studies.
- Most studies included patients with neuropathic pain. The effects of cannabis for people with other forms of chronic pain (such as low back pain or arthritis) have not been well studied.
- Whole-plant and CBD-predominant formulations remain essentially unstudied.
- Most of the information we have about cannabis and its effects on chronic pain come from studies of patients with neuropathic pain. Results of trials in neuropathic pain conditions may not be generalizable to other chronic pain conditions with different mechanisms, such as musculoskeletal pain.
- On average, formulations available in cannabis dispensaries (or from people who grow their own cannabis) tend to have a high ratio of THC to CBD and may be more potent than formulations evaluated in research studies.
- Typically, treatment of chronic pain continues for many months or years. We currently have no evidence examining the long-term (beyond 6 month) effects of cannabis for chronic pain.
- A substantial proportion of people who use cannabis daily or nearly daily develop cannabis withdrawal symptoms after stopping use. These symptoms, which include insomnia, anxiety, and irritability, can be severe enough to affect functional status and over half of patients using cannabis for chronic pain experience one or more of these symptoms.
- Cannabis use disorder may develop in 10-30% of individuals who use cannabis regularly. Emerging evidence suggests that non-medical cannabis use, and cannabis use disorder may be more common among those with chronic pain than those without chronic pain, though there is more to be learned about the frequency, severity, and risk factors for cannabis use disorder in patients who use cannabis exclusively for medical treatment of chronic pain.
Some patients with chronic neuropathic pain may experience small to moderate pain relief with cannabis, though the likelihood of achieving a clinically significant reduction in pain (defined as reducing at least 30% below baseline) did not differ based on randomization to cannabis or placebo. The patient populations with the best evidence supporting cannabis come from patients with neuropathic pain and the results may not generalize to those with musculoskeletal pain. The best studied cannabis formulation contains roughly equal amounts of THC and CBD, which may not be representative of what formulations patients actually use. Well-recognized short-term side effects of cannabis such as dizziness are common, but generally mild. Longer term adverse effects such as cannabis use disorder and cannabis withdrawal syndrome are concerns. The balance of benefits and harms from long-term use of cannabis for chronic pain is unclear.
Suggested citation: Morasco BJ, Kansagara D. Cannabis and Chronic Pain. Portland, OR: The Systematically Testing the Evidence on Marijuana Project; 2021. Updated Dec. 13, 2022. https://www.cannabisevidence.org/clinician-resources/clinician-briefs/cannabis-and-chronic-pain/
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