THC-rich cannabis oil significantly improved fibromyalgia symptoms in a small RCT | Research

The takeaway

In a small randomized trial of 17 women with fibromyalgia, THC-rich cannabis oil significantly reduced overall symptom scores compared to placebo, with improvements in feeling good, pain, ability to work, and fatigue.

Fibromyalgia patients, pain medicine clinicians, medical cannabis researchers

Cannabis group FIQ scores improved significantly vs. placebo (p = 0.005)

What the researchers found

After 8 weeks, the cannabis group showed significant FIQ score improvement vs. placebo (p = 0.005) and vs. baseline (p < 0.001). Specific improvements were seen in "feel good," "pain," "do work," and "fatigue" scores. The placebo group only improved on the "depression" score. No intolerable adverse effects occurred.

Why it matters

Fibromyalgia has limited effective treatments. This is one of the few RCTs testing THC-dominant cannabis oil specifically for fibromyalgia, showing significant improvement across multiple symptom domains.

The numbers in context

17 women; 8-week trial; THC oil: 24.44 mg/mL THC, 0.51 mg/mL CBD. Starting dose: ~1.22 mg THC/day. FIQ score significantly improved in cannabis group vs. placebo (p = 0.005) and vs. baseline (p < 0.001).

How the study worked

Double-blind, randomized, placebo-controlled trial. 17 women with fibromyalgia from a low-income neighborhood in Florianopolis, Brazil. THC-rich cannabis oil (24.44 mg/mL THC, 0.51 mg/mL CBD) starting at 1 drop/day with dose increases. Fibromyalgia Impact Questionnaire at baseline and 5 visits over 8 weeks.

What this study cannot tell us

Very small sample (17 participants); 8-week duration; specific population (low-income Brazilian women) may limit generalizability; no long-term follow-up; low starting doses.

How to read the evidence

Randomized, double-blind, placebo-controlled, but very small sample size (n = 17).

When this study was published

Published in 2020.

The bigger picture

This adds to emerging evidence that cannabinoids may help fibromyalgia, though the small sample means results should be interpreted cautiously until larger trials confirm these findings.

Questions still open

Would similar results appear in larger, longer trials? Is THC-dominant or CBD-dominant oil more effective for fibromyalgia? How do socioeconomic factors interact with treatment response?

Common questions

What was the starting dose of THC?

Patients started with approximately 1.22 mg THC per day (one drop), with subsequent increases based on symptoms. This is a very low starting dose, suggesting even small amounts of THC may provide benefit for fibromyalgia.

Were there significant side effects?

No intolerable adverse effects were reported during the 8-week trial. The researchers describe the treatment as well-tolerated, though the small sample limits the ability to detect rare side effects.

Read the original research

Ingestion of a THC-Rich Cannabis Oil in People with Fibromyalgia: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.

Pain medicine (Malden, Mass.), 21(10), 2212-2218

View on PubMed ↗Publisher’s paper ↗

Citation

Chaves, Carolina; Bittencourt, Paulo Cesar T; Pelegrini, Andreia. (2020). Ingestion of a THC-Rich Cannabis Oil in People with Fibromyalgia: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.. Pain medicine (Malden, Mass.), 21(10), 2212-2218. https://doi.org/10.1093/pm/pnaa303