Analgesic Effect of Cannabinoids for Fibromyalgia: A Systematic Review and Meta-Analysis.

BACKGROUND

Fibromyalgia is a kind of complex chronic pain syndrome that exerts a profound impact on patients' lives. Current pharmacological treatments for fibromyalgia often yield suboptimal results. Cannabinoids have emerged as a potential therapeutic alternative to these treatments.

OBJECTIVES

Our study aimed to assess the analgesic efficacy of cannabinoids in treating fibromyalgia.

STUDY

DESIGN

A systematic review and meta-analysis.

METHODS

We conducted a comprehensive literature search using PubMed (MEDLINE), EMBASE, ISI Web of Knowledge, Cochrane Library, and Clinicaltrials.gov to analyze randomized controlled trials and observational studies that investigated the analgesic efficacy of cannabinoids in individuals diagnosed with fibromyalgia. The primary outcome was the effect of cannabinoids on pain intensity, quantified by the standardized mean difference (SMD) in pain levels before and after the treatment. We registered our review protocol in PROSPERO (CRD42024495525). The quality of the evidence was evaluated using the Grade of Recommendations Assessment, Development, and Evaluation (GRADE) method.

RESULTS

Twelve clinical studies, consisting of 2 randomized controlled trials and 10 observational studies, (14 comparisons, 1,248 patients) were selected. Cannabinoids reduced pain intensity with statistical significance (SMD = -1.41, 95% CI = -1.98 to -0.84, P < 0.001), which was associated with a low GRADE rating. Both short-term (< 3 months, SMD = -1.37, 95% CI = -2.32 to -0.43, P = 0.004) and longer-term (≥ 3 months, SMD = -1.43, 95% CI = -2.22 to -0.65, P < 0.001) follow-ups showed statistically significant pain score reduction. Patients also experienced statistically significant improvements in sleep quality, anxiety, depression and quality of life (P-values < 0.05). Common adverse effects included dizziness, dry mouth, and drowsiness, while serious adverse effects were rare.

LIMITATIONS: Our analyses revealed that the results demonstrated considerable heterogeneity, which was attributed to variations in study designs, interventions, and outcome measurements across the included studies. These factors could potentially influence the validity of the findings. Thus, the results should be interpreted with these variations in mind.

CONCLUSION

Cannabinoids may provide analgesic benefits for patients with fibromyalgia. Cannabinoid use was also associated with improvements in sleep, anxiety, depression and quality of life. However, the findings should be interpreted with caution due to the quality of the evidence, heterogeneity, and small amount of available data from randomized controlled trials.