Excerpted from CBD: What Does the Science Say? by Linda A. Parker, Erin M. Rock, and Raphael Mechoulam, published by MIT Press (2022, 309 pp.).
A large proportion of medicinal cannabis patients are using cannabis to treat pain syndromes, particularly for chronic pain alleviation. Cannabis use for unmanageable pain has been shown to reduce the dose of opiates required to achieve pain control, suggesting opioid-sparing effects. Although no published clinical trials have clearly demonstrated this opioid-sparing effect with CBD alone, according to www.clinicaltrials.gov, registered clinical trials are investigating the interaction of CBD and morphine effects on pain sensitivity (NCT0403442) and abuse liability (NCT03679949).
Animal models suggest that CBD is generally ineffective in reducing acute pain when administered systemically, but this may be because insufficient amounts of CBD are reaching the brain to produce an analgesic effect. When CBD is combined with THC or morphine, it can potentiate the analgesic effects of these compounds to relieve acute pain, and analogs of CBD also seem to have analgesic effects in acute pain models in animals.
In animal models of neuropathic pain, CBD is effective in preventing the development of certain types of chemotherapy- and diabetes-induced pain, as well as the treatment of already established chemotherapy-, spinal cord injury-, or post-operative-induced neuropathic pain. Indeed, a clinical study with topical CBD improved pain ratings in neuropathic pain patients. Nabiximols [an oromucosal tincture with 2.7 mg THC and 2.5 mg CBD per spray] has also been shown to reduce pain and allodynia in neuropathic pain patients, with improvements maintained for an entire year.
In animal models, when administered prior to or following the initiation of inflammation or arthritis, CBD can abolish neuropathic pain symptoms and reduce the associated swelling. Nabiximols (marketed as Sativex) has also been shown to reduce pain in rheumatoid arthritis patients who were unresponsive to standard treatments. These findings suggest that CBD may be an adjunct treatment to investigate in inflammatory pain conditions such as arthritis.
CBD’s anti-inflammatory effects have also been demonstrated in animal models of brain injury due to interrupted blood flow to the brain. CBD treatment within eighteen hours can reduce brain cell damage and inflammation and restore brain activity. In animal and cellular models of gastrointestinal tract inflammation, CBD has anti-inflammatory effects and restores the integrity of the gut lining. A handful of human studies also suggest that CBD may improve inflammatory bowel disease symptoms and restore intestinal integrity, but further research is needed.
Sublingual spray-delivered CBD alone (as well as nabiximols) reduced pain and spasticity scores in multiple sclerosis patients, and topical application of CBD relieved myofascial pain and neuropathic pain. To date, nearly fifty clinical trials registered at www.clinicaltrials.gov are investigating the ability of CBD (alone or in combination with THC) to reduce pain associated with conditions such as tooth extractions, chronic back pain, postsurgical pain, diabetic neuropathy, and cancer pain. These important properly controlled randomized clinical trials will help to better understand the potential analgesic properties of CBD.
About the authors of CBD: What Does the Science Say? published by MIT Press: Linda Parker is Professor Emeritus in the Psychology and Collaborative Neuroscience Program at the University of Guelph in Ontario and author of Cannabinoids and the Brain (MIT Press). Erin M. Rock is a Postdoctoral Fellow and Adjunct Faculty member in the Psychology and Collaborative Neuroscience Program at the University of Guelph. Raphael Mechoulam, often called “the father of cannabis research,” is the Lionel Jacobson Professor of Medicinal Chemistry at Hebrew University in Jerusalem and winner of the 2019 Harvey Prize for outstanding contributions to science and technology.