Cannabis products with high levels of THC offer mild, short-term improvements in pain management, but with side effects.
Cannabis preparations with high levels of tetrahydrocannabinol (THC) could offer a limited and short-lasting reduction in chronic pain, especially neuralgia, but with a higher risk of common side effects, such as nausea, dizziness or sedation. In contrast, cannabis products that contain only cannabidiol or CBD, which are most often used for the management of chronic pain, do not appear to have any pain relief benefits compared to placebo. It is the conclusion of a review of new controlled studies on the topic, published in the scientific journal Annals of Internal Medicine.
Against a cliché
«This fact may be surprising, because it was widely believed that CBD was promising because it does not give the euphoric effects of THC, but it was thought to have medicinal properties. However, at least according to our analysis, it has not been shown to have effects against pain” explains Roger Chou, Professor of Clinical Epidemiology at Oregon Health & Science University and coordinator of the study.
Together with colleagues, Chou analyzed 25 randomized (i.e. participants were randomly assigned to different treatment groups) placebo-controlled clinical trials of cannabis products to update previous scientific guidelines on their effectiveness against chronic pain.
THC: the effects on pain
THC and CBD are the two best known of the 113 different cannabinoid compounds found in cannabis. The cannabis plant, in nature, is thought to use cannabinoids to defend itself from insects, bacteria, fungi and environmental stressors. Tetrahydrocannabinol (THC) is the active ingredient commonly associated with the narcotic effect of cannabis, while cannabidiol (CBD) is a non-psychoactive compound, which gives a feeling of relaxation.
Until now, it has been thought that both of these substances act on the endocannabinoid system, a biological mechanism that controls, among other things, the modulation of pain. THC and CBD are contained in various products that in many states – including Oregon, where the study was conducted – are used pharmacologically to sleep, relieve chronic pain or reduce anxiety. The legal situation of these products in Italy is more complicated and still evolving (to learn more).
Both the original (2022) review and the new addition found that oral products containing predominantly THC slightly reduce pain intensity in the short term, although they were linked to moderate to large increases in dizziness, nausea and drowsiness.
The effect on pain (especially neuropathic pain, i.e. caused by damage to the peripheral or central nervous system), is however very small, of an order of magnitude of half a point compared to placebo on a scale of 0 to 10.
CBD and pain: bitter surprise
What about CBD? Products based on this substance, more commonly available in pharmacies – and often referred to as “cannabis light” – have not demonstrated any significant effect in reducing pain in the studies analyzed, even though many people use them and are convinced of their effectiveness.
“Our goal is to provide some scientific basis so that people can make informed decisions,” explains Chou. He adds that the issue «is complicated because cannabis-based products are complicated. It’s not like taking a standard dose of ibuprofen: cannabis comes from a plant that contains many chemicals in addition to THC and CBD, which may have additional properties depending on where the plant was grown or processed for sale.”
