Medicinal cannabis products show promise as a treatment for fibromyalgia, with patients reporting improvements across all measured outcomes, according to a new study using data from the UK Medical Cannabis Registry (UKMCR).
The study of 497 patients found improvements in fibromyalgia-specific symptoms, with the greatest effects seen in the short to medium term. Higher doses of cannabidiol (CBD) – above 25mg daily – were associated with better outcomes, whilst being a current cannabis user before treatment also produced better results.
Fibromyalgia is a condition that is defined primarily by symptoms of widespread chronic pain lasting more than three months. People living with the condition also report multiple accompanying somatic symptoms, including waking up after a long sleep feeling unrefreshed, experiencing ‘brain-fog’ or being unable to think clearly, and symptoms of depression.
Currently, there is no cure for fibromyalgia. Medicinal treatment options are limited; they include anti-convulsants such as pregabalin and gabapentin, and antidepressants such as duloxetine, amitriptyline, and milnacipran. While patients have reported positive outcomes after treatment with these medicines, the amount of relief they provide can be much less than the patient requires.
Traditional treatments also come with significant side effects, including dizziness, weight gain, lack of motivation and sleep problems. The high level of these adverse effects contributes to high discontinuation rates, with one study finding that around 72% of fibromyalgia patients fail to take prescriptions as instructed.
Previous studies have found cannabis effective for pain reduction, sleep improvement, cognitive function and mood – symptoms that overlap significantly with fibromyalgia. Researchers aimed to evaluate patient-reported outcome measures (PROMs) and adverse effects (AEs) in fibromyalgia patients treated with cannabis-based medicinal products (CBMPs).
Using data from the UK Medical Cannabis Registry (UKMCR) – which contained information on 19,763 UK cannabis patients as of December 2023 – researchers analysed 497 fibromyalgia patients after applying exclusion criteria.
The cohort was 68.6% female with an average age of 44.7 years. Just over half were unemployed, and nearly a third were current tobacco smokers. More than half (53%) were current cannabis users, 15% had previously used cannabis, and 31% had never used it.
Patients were assessed at the start of the study, and again at 1, 3, 6, 12, and 18-month intervals. The assessments included questions on fibromyalgia symptom severity, pain levels, anxiety, depression, mobility, self-care, and the ability to take part in regular activities.
Initially, all patients were prescribed a cannabis oil, but as the study progressed, most began to take a mixture of oils and flowers. The median CBD dosage increased throughout the study, from 20mg a day at the start to 25mg at the end of the study. THC content also increased as the study progressed, from a median of 2mg a day at the beginning of the study to 112.5mg at the end.
After analysing the results, researchers found cannabis treatment to benefit patients in all of the recorded outcomes, although the greatest effects were seen in the short to medium term.
“This study found improvements in fibromyalgia-specific PROMs at a long-term follow-up of 18 months, although these gradually declined over time, with peak improvement from baseline seen at 1 month and lowest at 18 months. A previous UKMCR fibromyalgia analysis showed similar trends, possibly due to cannabis-induced hyperalgesia. Similar to opioid-induced hyperalgesia, patients may experience increased pain sensitivity and decreased pain tolerance with long-term exposure to CBMPs. However, further research and longer-term studies are warranted in studying this phenomenon,” the author wrote.
Notably, higher CBD doses were associated with better outcomes compared to lower doses, and current cannabis users saw better results than those who had never used it. However, higher THC doses were not associated with increased odds of improvement in any of the measures.
Nearly half of the participants (45.67%) reported adverse effects, with 2,100 AEs recorded in total. Researchers believe the high rate relates to fibromyalgia’s central sensitisation mechanism, where increased nervous system sensitivity may enhance responses to new stimuli. Most adverse effects (85.33%) were mild to moderate, with fatigue being the most common (30.78%). Women reported higher levels of adverse effects than men.
“The high incidence of AEs relative to other studies from the UKMCR may reflect the central sensitisation mechanism in fibromyalgia, where increased dorsal horn neuron excitability could enhance responsiveness to new stimuli, such as CBMPs, and even formerly innocuous stimuli. Furthermore, research suggests that females report more AEs than males, which is important to consider given that 68.61% of patients in this study were female,” the study author wrote.
The researchers concluded that CBMPs were associated with improvement in symptoms, stressing that while this real-world data can inform clinical decisions, more randomised controlled trials were needed to consolidate the findings.
“This study found treatment with CBMPs in fibromyalgia was associated with short to medium-term improvements in pain, anxiety, sleep, and general quality of life. There was a high incidence of AEs, perhaps due to its central sensitisation mechanism, associated with an increased susceptibility to AEs. However, these findings must be interpreted within the limitations of the study design. More randomised controlled trials are warranted, but this large analysis provides real-world data to inform their conduct,” the author concluded.
