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Cannabidiol Not an Effective Analgesic for Fibromyalgia in Single-Center Study
Study data favored the placebo group, although differences were not clinically meaningful.
A single center study has found that cannabidiol (CBD) 50 mg did not reduce pain compared to placebo in people with fibromyalgia.1
“There is a lack of evidence from high-quality dose-response and well-powered pharmacokinetic studies to inform clinical practice on the appropriate dosing and administration of CBD for achieving clinical effectiveness. This gap necessitates expert guidance and treatment protocols based on expert consensus for its clinical use in the treatment of chronic pain, including fibromyalgia. Given the limited evidence, this treatment option remains inaccessible to patients, leading some to self-administer unlicensed medical cannabis at their own risk and expense.2 Thus, well-designed randomized trials are warranted,” study investigator Marianne Uggen Rasmussen, RN, PhD, and colleagues wrote.1
Rasmussen and colleagues investigated the safety and efficacy of CBD compared to placebo in a single-center, double-blind, randomized, placebo-controlled study of 273 participants diagnosed with fibromyalgia recruited from a specialized outpatient clinic in Denmark. Eligible participants (n = 200) were randomized 1:1 to receive 50 mg plant-derived CBD (n = 100) or placebo (n = 100) and stratified by sex, defined as biological sex assigned at birth based on physical anatomy. Participants were either cannabis-naïve or had not used cannabis within the last 6 months. They had a mean age of 49.9 years (SD, 10.7) and 189 (94.5%) were female. The study’s primary outcome was change in pain intensity at week 24, assessed on the numerical rating scale (NRS) pain subitem in the revised Fibromyalgia Impact Questionnaire (FIQ) in the intention-to-treat population.
In the CBD group, 83 participants completed week 24, while 10 were lost to follow-up and 7 discontinued due to adverse events (AEs). In the placebo group, 86 completed week 24, with 7 lost to follow-up and 7 discontinuing because of AEs. Among those using CBD, 67 reached the maximum maintenance dose of 50 mg daily, 18 completed at 40 mg daily, and 1 at 30 mg. In the placebo arm, 74 achieved the maximum dose, 3 completed at 40 mg, 3 at 30 mg, 2 at 20 mg, and 1 at 10 mg daily. Protocol deviations were reported in both groups, with 5 participants in the CBD group and 2 in the placebo group requiring opioid treatment for nonrelated AEs.
The investigators found that at week 24, the mean change in pain intensity was -0.4 points (95% CI, -0.82 to 0.08) in the CBD group and -1.1 points (95% CI, -1.53 to -0.63) in the placebo group, corresponding to a between-group difference of -0.7 points (95% CI, -1.2 to -0.25; P = .0028) slightly favoring placebo, although this was not clinically meaningful.
AEs were mostly mild and rates were similar between groups. The most frequent AEs considered probably related to the study medication were headaches/migraines, worsening in fatigue, nausea/vomiting, diarrhea, and dryness of the mouth/throat. There were 10 serious AEs reported during the study, but these were all hospitalizations due to other and unrelated reasons and were not related to the study medication.
The investigators noted limitations of the study, including its single-center nature, predominantly female population, and the lack of data on the proportion of participants with prior experience with cannabis or related products before the 6-month period in either group.
“In conclusion, our study did not support analgesic efficacy of treatment with CBD 50 mg daily compared to placebo in patients with fibromyalgia. Furthermore, the study did not show beneficial effects of CBD on other core outcomes such as functional ability, quality of sleep, and quality of life in this patient population. The study results do not support the use of CBD as an analgesic supplement in fibromyalgia,” Rasmussen and colleagues wrote.1
References
Rasmussen MU, Christensen R, Wæhrens EE, et al. Cannabidiol versus placebo in patients with fibromyalgia: a randomised, double-blind, placebo-controlled, parallel-group, single-centre trial. Ann Rheum Dis. Published online August 21, 2025. doi:10.1016/j.ard.2025.07.008
Khurshid H, Qureshi IA, Jahan N, et al. A Systematic Review of Fibromyalgia and Recent Advancements in Treatment: Is Medicinal Cannabis a New Hope?. Cureus. 2021;13(8):e17332. Published 2021 Aug 20. doi:10.7759/cureus.17332
