Evidence for the Use of Medical Cannabis for the Treatment of Fibromyalgia Syndrome

Evidence assessing if Medical Cannabis is appropriate as a Treatment for Fibromyalgia Syndrome

Fibromyalgia syndrome is a chronic pain condition that has been found to have a significant impact on the quality of life of patients. Chronic pain has been estimated to affect around 43% of the UK population, with 14.3% living with conditions that are either moderately or severely disabling. According to the NHS, almost 1 in 20 people in the UK may be affected by fibromyalgia to some degree. 

There is no known cure for fibromyalgia syndrome as the exact cause of the condition is unknown and symptoms can vary from person to person. Common treatments for fibromyalgia focus on symptom management. This can include medicines such as antidepressants and painkillers as well as talking therapies and lifestyle changes. 

The need for more effective treatment options for fibromyalgia, as well as for other chronic pain conditions, is at an all-time high, as the risk of addiction and diminishing efficacy of opioid-based medications becomes increasingly recognised.

Medical cannabis as a treatment for Fibromyalgia

In recent years, research into the potential of medical cannabis for the treatment of chronic pain conditions has been on the rise. A number of studies and trials have assessed the potential of medical cannabis in chronic pain conditions, but few of these have focused specifically on fibromyalgia syndrome.

However, the few studies that have been conducted yielded promising results supporting the potential of medical cannabis and cannabinoids. The authors of a recent study of medical cannabis in fibromyalgia patents in Italy aimed to build on the current evidence in this area. 

The Aims and Methods of the Study

This was a retrospective study that aimed to assess the analgesic potential and adverse events of medical cannabis in fibromyalgia patients who were deemed resistant to first-line medications. Patients were evaluated to assess the effects of licensed medical cannabis products on pain intensity, disability, widespread pain, disease severity, and mood disorders.

Participants of this study were recruited at the pain clinic of Ponderano in Biella, Italy. Out of 75 patients who presented at the clinic between June 2016 and October 2018, 36 patients were deemed eligible for participation. Most excluded patients did not meet all inclusion criteria or had not tried all conventional treatment options.

Participants received licensed medical cannabis products which included cannabidiol (CBD) and tetrahydrocannabinol (THC). Treatment was provided in either plant form (used for decoction or vaporisation) or as oil extracts. Data was collected after 1, 3, and 12 months using a number of measures.

Data Collection

The primary endpoint, pain relief, was evaluated with a numerical rating scale (an 11-point scale used by patients to report pain, with 0 indicating no pain, and 10 indicating maximum pain). Analgesic effects were considered when patients reported a reduction in pain intensity by at least 30%. The secondary outcome, adverse events, were recorded by the physician at monthly follow-up visits.

Disability was recorded using a validated Italian version of the Oswestry Disability Index (ODI) – a test evaluating intensity of pain and its impact on daily activities. Mood disorders were also evaluated with the Hospital Anxiety and Depression Scale (HADS).

Results of the Study

Following initial prescription of medical cannabis, five patients discontinued therapy due to side effects including vomiting, headache, nausea, dry mouth, and palpitations. A total of 30 patients continued medical cannabis therapy for at least a month and were included in the endpoint analysis.

At the one-month follow-up visit, 20 of the 30 patients reported analgesic (pain-relieving) effects – 17 of which reported no side effects. However, three patients reported mild side effects and chose to discontinue therapy.

 Of the 10 patients who did not experience analgesic effects, nine had no, or mild side effects and discontinued treatment. One patient experienced no analgesic effects but reported improvements in sleep duration, hence deciding to continue therapy. 18 patients continued treatment until at least three months.

Between the 3-month and 12-month follow-up visit, six patients discontinued medical cannabis treatment. However, patient drop-out at this time was largely unrelated to medical cannabis treatment itself (e.g. moved to other regions, no longer able to obtain medical cannabis). One patient discontinued therapy as they were worried about driving. A total of 12 patients completed treatment or at least 12 months. 

Analgesic Efficacy

Data collected throughout the study period revealed the medical cannabis therapy reduced pain significantly at 1, 3, and 12 months by at least 30%. Of the 17 patients who experienced pain reduction, five (14%) had a decrease in pain intensity of between 30-50%. Twelve patients (34%) had a decrease in pain intensity of over 50%. 

Side Effects

A total of 17 patients (48.6%) experienced side effects relating to medical cannabis treatment. All side effects were mild and were quickly reversed following the cessation of treatment. The most common side effect recorded was mental confusion. 

Other Results

In addition to improvements in pain intensity, a significant improvement in disability was also recorded at each time point. However, no significant improvements were recorded in HADS anxiety and depression indexes at all time points. 

SyS scores (a test that assesses fatigue, waking unrefreshed, cognitive symptoms, and other somatic symptoms) were also seen to improve significantly over all time points.


The findings of this study can be compared with previous data collected in this area. In addition to promising results regarding pain reduction and improvements in disability, it was recorded that some patients were able to reduce their use of other medications. For example, 66.7% of responsive patients used medical cannabis alone; 50% of patients discontinued the use of other medications and 46% reduced the dose/number of medications by at least 50%.

This study revealed the positive potential of medical cannabis for the treatment of some patients with treatment-resistant fibromyalgia. However, there is concern due to the study dropout rate secondary to side effects. Further research is warranted to gain a clearer picture of both the analgesic effect and side effects caused by these products.