# UK Medical Cannabis Registry: a case series analysing clinical outcomes of medicinal cannabis therapy for fibromyalgia

## TL;DR

A study of 497 patients found that medical cannabis improved pain, anxiety, and sleep in fibromyalgia patients, though many experienced mild side effects.

## Contribution

This is one of the largest real-world analyses of medical cannabis for fibromyalgia, showing consistent improvements across multiple outcomes.

## Key findings

- Patients showed significant improvements in pain, anxiety, sleep, and quality of life after using cannabis-based products.
- Higher CBD doses and prior cannabis use were linked to better outcomes in fibromyalgia-specific measures.
- Most adverse events were mild to moderate, with fatigue being the most common side effect.

## Abstract

Fibromyalgia is a common condition characterised by widespread chronic pain, associated with comorbid mental health disorders and reduced quality of life. Preclinical data suggest cannabis-based medicinal products (CBMPs) may have potential benefits in fibromyalgia, but there is a paucity of high-quality clinical evidence. This study aims to assess the change in patient-reported outcome measures (PROMs) and incidence of adverse events (AEs) in patients treated with CBMPs for fibromyalgia.

This case series analysed data from the UK Medical Cannabis Registry (UKMCR). The primary outcome was change in PROMs [Fibromyalgia Symptom Severity, Fibromyalgia Widespread Pain Index, EQ-5D-5L, Generalised Anxiety Disorder-7, and Single-Item Sleep Quality Scale] from baseline to follow-up at 1, 3, 6, 12, and 18 months. Statistical significance was defined as p < 0.050.

Four hundred ninety-seven patients were included. The mean age was 44.66 ± 12.02 years, 341 patients (68.61%) were female, and the majority of patients were unemployed (n = 268, 53.92%). There was an improvement in all PROMs (p < 0.010) from baseline to all follow-up periods. Higher CBD doses (> 25.00 mg/day) and previous cannabis use were associated with increased odds of improvement on fibromyalgia-specific scales (p < 0.050). 227 patients (45.67%) reported 2100 AEs (422.54%). Most AEs were mild-to-moderate (n = 1792, 85.33%). The most common AE was fatigue (n = 153, 30.78%).

There was an association between treatment with CBMPs and improvements in pain, anxiety, sleep, and general quality of life. The high incidence of AEs in relation to other patient cohorts from the UKMCR may relate to the central sensitisation mechanism of fibromyalgia.

Key Points

• This study found that CBMPs were associated with short to medium-term improvements in pain, anxiety, sleep, and general quality-of-life in patients with fibromyalgia.

• More randomised controlled trials are warranted to consolidate the literature, but this large analysis provides real-world data to inform their rollout.

The online version contains supplementary material available at 10.1007/s10067-025-07846-6.