Fibromyalgia is a common chronic pain condition that is characterised by chronic widespread musculoskeletal pain, generalised hyperalgesia, and psychological distress. Some estimates suggest that around 1 in 20 people may be affected by fibromyalgia to some degree; however, the condition is often difficult to diagnose, as there is no specific test for the condition.
Fibromyalgia can have a significant impact on quality of life, affecting sleep, mobility, and mood. Currently, fibromyalgia is a significant unmet clinical need, making the development of new, effective therapies an important area of research.
As cannabis research continues to advance, a number of studies have found evidence to support the use of cannabinoids in the setting of pain. Cannabis has a long history as an analgesic, however, due to long-term prohibition in the 20th century – which continues to affect research – limited clinical evidence has been collected to support this use.
The Endocannabinoid System is a receptor system expressed throughout the central nervous and immune systems. Evidence shows that this system plays a significant role in cognitive and physiological processes in humans, including mood regulation and pain signalling. Clinically, there is also evidence for alterations in the endocannabinoid system in patients with fibromyalgia.
A recent review of clinical and preclinical research aimed to analyse the existing evidence concerning the role of cannabinoids and the endocannabinoid system in fibromyalgia.
Evidence of Fibromyalgia Comorbidities
As mentioned, fibromyalgia is often associated with reduced quality of life which may be linked to effects on sleep quality, reduced mobility, and prevalence of psychiatric comorbidities such as anxiety and depression. A recent review revealed the prevalence of current and lifetime depression in fibromyalgia patients was 43% and 63%, respectively. Furthermore, the prevalence of lifetime and/or current anxiety disorders concurring with FM have been reported in numerous studies with a high degree of variability, ranging from 30 to 80%.
Fibromyalgia may also be accompanied by other somatic comorbidities such as irritable bowel syndrome (IBS) and migraine. Research suggests a bi-directional relationship between fibromyalgia and IBS with the prevalence of fibromyalgia in patients with IBS ranging from 32 to 77% and the prevalence of IBS in patients with FM ranging from 28 to 65%.
Cannabinoids and Fibromyalgia
A number of animal studies have aimed to determine how cannabinoids may influence fibromyalgia. Following analysis of existing evidence, the researchers conclude that drugs that enhance cannabinoid 1 (CB1) receptor activation could be useful for both pain and other symptoms of fibromyalgia.
Various studies have assessed the potential of cannabis-based therapies for fibromyalgia. The findings indicate that inhaled cannabis may be beneficial in pain, quality of life, and sleep. Furthermore, patient-reported outcomes from various trials indicate the potential of cannabinoid-based drugs in fibromyalgia. Many trials also note the favourable adverse event trials of cannabinoid-based medicines in comparison to alternative therapies.
Nonetheless, the researchers note that there is currently not enough high-quality evidence to support this. To address this, it is recommended that more high quality randomised controlled trials (RCTs) be conducted in this area.
Medical Cannabis in Common Comorbidities of Fibromyalgia
A recent cross-sectional study of medical cannabis users in Illinois, USA, found that almost 50% of responders reported severe fibromyalgia. Of this subgroup, pain was the most frequently reported use for medical cannabis (74.9%), followed by anxiety (65.7%), insomnia (56.4%) and depression (49.3%). Interestingly, 75.5% of responders reported two or more of these symptoms, suggesting a high symptom burden.
There is a growing body of evidence supporting the potential benefits of medical cannabis for many of the common comorbidities associated with fibromyalgia including IBS, anxiety, and depression.
In this review, researchers note that several RCTs have investigated the use of CBD for anxiety. Overall, these studies suggest that CBD is effective at reducing self-reported anxiety scores and social anxiety. The researchers did not identify any RCTs investigating the effect of cannabinoids on symptoms of fibromyalgia and chronic overlapping conditions such as anxiety, depression, and IBS.
Conclusions
Overall, the researchers note that the current scarcity of high-quality evidence makes it “difficult to draw any robust conclusions or make recommendations for the use of cannabis-based medicines from the treatment of [fibromyalgia].” Nonetheless, given promising results from existing trials in some areas, it is recommended that further research be conducted.
Medical cannabis may now be considered for fibromyalgia where first-line therapies have failed to achieve satisfactory results.
