What fibromyalgia is
Fibromyalgia is a chronic condition characterised by widespread musculoskeletal pain, persistent fatigue, unrefreshing sleep, cognitive difficulties (sometimes called fibro-fog), and heightened sensitivity to sensory input. The condition affects an estimated 2 to 4 per cent of the UK population and is diagnosed more often in women than men.
The underlying biology of fibromyalgia is not fully understood. The leading explanation is central sensitisation: the central nervous system amplifies pain signals so that normally non-painful stimuli become painful and mildly painful stimuli become intensely painful. Research has also identified abnormalities in neurotransmitters, stress hormone regulation, sleep architecture, and the autonomic nervous system. There is no single diagnostic test; diagnosis is clinical, based on symptom history and the exclusion of other conditions.
Standard management in the UK, as set out in the Royal College of Physicians guidelines and NICE guidance for chronic pain, includes graded exercise, cognitive behavioural therapy, and medicines such as amitriptyline, duloxetine, and pregabalin. Outcomes vary considerably between individuals.
Cannabis research on Fibromyalgia
The evidence base available for fibromyalgia is extremely thin. A single internal library page matched the search, and it is a lifestyle magazine article naming fibromyalgia in a list of conditions where people have turned to cannabis. It is not clinical evidence.
The published research literature contains limited human studies, and no large, definitive randomised controlled trial.
Nabilone, a synthetic cannabinoid that acts as a THC analogue at CB1 receptors, has been tested in two small randomised controlled trials for fibromyalgia. A 2008 Canadian trial with 40 participants found that nabilone, compared with placebo, was associated with a statistically significant reduction in pain and improvement in sleep quality measured by the Fibromyalgia Impact Questionnaire (FIQ) in a human clinical study. A separate 2010 trial of nabilone for sleep in fibromyalgia, with 32 participants, reported improved sleep in a human clinical study.
An experimental human laboratory study from the Netherlands, published in 2019, tested inhaled cannabis containing THC in women with fibromyalgia. The study measured electrically evoked pain thresholds and spontaneous pain scores. Inhaled cannabis did not alter electrical pain thresholds versus placebo. Spontaneous pain scores decreased, but the study was small (25 participants) and conducted as an acute laboratory experiment, not a treatment trial.
Human observational studies from Israel have reported that some people with fibromyalgia who use cannabis describe reduced pain and improved quality of life. However, observational data cannot distinguish a pharmacological effect from placebo response, recall bias, or natural fluctuation in symptoms. People who choose to use cannabis and then report on it are a self-selected group not representative of the whole fibromyalgia population.
Biological plausibility evidence includes laboratory findings of altered circulating endocannabinoid levels in people with fibromyalgia, and the known presence of CB1 and CB2 receptors in pain-processing brain regions and on immune cells. These biological observations identify candidate mechanisms but do not establish that cannabis affects fibromyalgia symptoms. A mechanism can exist without an effective treatment.
Compounds studied for Fibromyalgia
THC has been tested in fibromyalgia as the synthetic analogue nabilone in human randomised controlled trials, and as inhaled cannabis in a human experimental laboratory study. The two nabilone trials reported reductions in pain and improved sleep, but both enrolled fewer than 50 people.
CBD has not been studied in completed human randomised controlled trials for fibromyalgia as an isolated compound. A clinical trial of CBD for fibromyalgia is ongoing (NCT04520685), but results are not yet published. CBD’s activity at serotonin 5-HT1A receptors and its anti-inflammatory properties in animal models are laboratory findings, not clinical evidence for fibromyalgia.
CBG has not been tested in any human fibromyalgia study. Cell and laboratory studies show CBG interacts with alpha-2 adrenoceptors and TRPV1 channels, both relevant to pain signalling, but this is preclinical evidence only.
Beta-caryophyllene is a CB2 receptor agonist. Animal research demonstrates anti-inflammatory and anti-nociceptive effects, but fibromyalgia-specific animal models are limited and human data is absent.
Myrcene has shown muscle-relaxant and anti-nociceptive effects in animal research, but there are no human fibromyalgia studies of myrcene.
Linalool has been studied in animal models for sedative and anti-anxiety effects, but there are no human fibromyalgia trials.
Limits of the evidence for Fibromyalgia
The evidence base for cannabis and fibromyalgia is among the weakest of any condition examined in this series. No randomised controlled trial of whole-plant cannabis for fibromyalgia has been published. The two nabilone trials combined enrolled fewer than 80 people and were of short duration. The experimental laboratory study tested acute effects on pain thresholds, not long-term treatment outcomes.
Fibromyalgia is a complex, multi-system condition with variable presentation. Pain levels, fatigue, sleep quality, and cognitive function all interact. Measuring a single outcome such as pain intensity in a short trial may not capture whether cannabis makes a meaningful difference to daily living.
The observational data from Israel comes from a population with access to a regulated medical cannabis programme. These findings may not transfer to a UK population, where cannabis-based medicinal products are prescribed under different clinical criteria and are not routinely available for fibromyalgia.
NICE guideline NG144 (2021) does not recommend cannabis-based medicinal products for chronic pain. Fibromyalgia falls within the chronic pain category that NICE reviewed, and no fibromyalgia-specific exception was made.
Sources
1. Skrabek RQ, Galimova L, Ethans K, Perry D. Nabilone for the treatment of pain in fibromyalgia. Journal of Pain. 2008;9(2):164-173. Study record
2. Ware MA, Fitzcharles MA, Joseph L, Shir Y. The effects of nabilone on sleep in fibromyalgia: results of a randomized controlled trial. Anesthesia and Analgesia. 2010;110(2):604-610. Study record
3. van de Donk T, Niesters M, Kowal MA, Olofsen E, Dahan A, van Velzen M. An experimental randomized study on the analgesic effects of pharmaceutical-grade cannabis in chronic pain patients with fibromyalgia. Pain. 2019;160(4):860-869. Study record
4. Habib G, Artul S. Medical cannabis for the treatment of fibromyalgia. Journal of Clinical Rheumatology. 2018;24(5):255-258. Study record
5. NICE. Cannabis-based medicinal products. NICE guideline NG144. Published 11 November 2019, updated 22 October 2021. Study record
