The use of cannabis for medical purposes is now legal in more than 30 states in the United States. Better understanding and characterizing the impact of cannabis and cannabinoids on different pathways of pain reactivity may help explain the belief that cannabis relieves pain and support evidence of efficacy. “But we still have a lot to learn,” concludes this team from Syracuse University in JAMA Psychiatry, which suggests that while cannabinoids do not reduce the intensity of pain, they make it less unpleasant and more tolerable. .
This publication coincides with “Pain Awareness Month” and is the first-ever systematic review of experimental research on the effects of cannabis on pain. Cannabinoids are chemical compounds that give the cannabis plant its medicinal and recreational properties. The main author, Martin De Vita, doctoral candidate in clinical psychology, recalls that THC and CBD (cannabidiol) are the main cannabinoids. When ingested, THC binds to receptors in the brain that control pleasure, time perception, and pain. This activity leads to the production of dopamine with an effect of euphoria or relaxation.
However, better quality evidence supporting the efficacy of cannabis in the treatment of chronic pain remains to be established. “While patients are convinced that cannabis is effective in relieving pain, its analgesic properties remain poorly understood. explains the lead author, who recalls that so far experimental studies of cannabinoid analgesia in healthy adults have yielded mixed results. It is therefore a very broad review of the literature that is proposed to us, with more than 1,830 experimental studies on cannabis identified, carried out in North America and Europe over a period of 40 years. Then the meta-analysis of the 18 selected studies involving 440 adult participants. The mean study quality and validity score was high and the analyzes did not suggest publication bias. The analysis finds that cannabinoid drugs are associated with:
- modest increases in pain threshold and tolerance,
- but on the other hand to no reduction in the intensity of the “ongoing” pain.
Cannabinoids therefore allow a reduction in the unpleasantness of painful stimuli and do not lead to any mechanical reduction in hyperalgesia.
An affective rather than sensory effect? Cannabinoid analgesia could thus be linked to an affective component rather than a sensory component. Anyway, as far as THC is concerned. Because studies have mostly focused on THC strains, it's unclear whether other cannabinoids exert different effects on pain.
The analysis having been limited to experimental pain, that is to say induced in the laboratory, the team will now continue its research on clinical pain , generally associated with a non-malignant progressive disease and on neuropathic pain , associated with disease or damage to the nervous system, leading to tissue damage.