Chronic pain affects a large proportion of the global population and is often difficult to treat successfully. The condition can have lasting effects on patients’ psychological wellbeing and lifestyle. Increasing attention and research is being extended to the potential of medical cannabis for both pain management and quality of life in relation to chronic pain.
Chronic pain is one of the most common global causes of disability, affecting around 13% of adults in the UK. The condition can be caused by a variety of factors, including trauma, arthritis, surgery, cancer, and fibromyalgia. Chronic pain requires a multimodal treatment approach that seeks to identify and treat any underlying disorder as well as provide appropriate pain relief.
Treatments for Chronic Pain
Many chronic pain patients find traditional pharmaceutical medications are ineffective and often not well tolerated. Opioids are often prescribed to chronic pain patients despite their effects being better characterised for acute pain. This class of medications is also known to have high abuse potential and significant adverse effects.
Due to the paucity of available treatment options, there is a growing desire to identify novel treatment agents. Whole-flower cannabis has been found to have analgesic (pain-relieving) properties. This has led to many researchers considering its potential as a replacement or supplemental therapy for chronic pain, both as a whole flower product and as isolates of constituent cannabinoids, namely (−)-trans-Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD). A recent observational study, published in Pain Medicine, aimed to assess this potential.
Medical Cannabis and Chronic Pain
The pain-relieving ability of cannabis and cannabinoids has been demonstrated in a number of preclinical and clinical studies. However, some trials and studies have also drawn inconclusive results due to the diverse study design, patient population, and study medications.
Study Design
A prospective, observational, longitudinal, open-label study design was used to evaluate the analgesic effectiveness of plant-based medical cannabis and the quality of life of participating patients during treatment. A total of 751 chronic pain patients participated in the study, which took place over a one-year study period.
Participants were asked to complete study questionnaires at baseline (before medical cannabis treatment) and once a month for 12 months. Each participant was prescribed a personalised treatment plan with specific dosing instructions, route of administration, and THC limit based on medical histories, needs, and tolerability.
Pain and Quality of Life was assessed via self-reported rating scales:
The Brief Pain Inventory (BPI) was used to record Pain Severity (0 = no pain; 10 = pain as bad as you can imagine) and Pain Interference (0 = does not interfere; 10 = completely interferes) for each patient at these time points.
Quality of Life was recorded using a Short-Form Health Survey, assessing 12 aspects of life quality. Physical Composite Summary (PCS) and Mental Composite Summary (MCS) scores were calculated in order to assess changes in patient quality of life throughout the study length.
Some patients continued with existing pain relief throughout the study period. These patients were asked to provide the name and dosing details of these medications to allow researchers to draw comparisons across patients using different types of opioid medications.
The Results
Pain Severity and Pain Interference scores saw a significant improvement from as early as one month into the study period. For participants who continued with the study to completion, this improvement was maintained. At baseline (prior to medical cannabis treatment) the mean Pain Severity score was 5.58 – indicating moderate to severe pain. At month 12, the mean Pain Severity score was reduced to 3.49 – indicating mild to moderate pain and a 2.09-point reduction.
The researchers of this study point out that these improvements in pain appeared to be associated with positive effects on the patients’ health-related quality of life. This was supported by the improvements observed in measures of physical and mental health.
This study concluded that the treatment of chronic pain with medical cannabis was associated with significant improvements in pain and health-related quality of life.
For those patients on opioid medications, there was a significant reduction in their prescribed dose from baseline, calculated according to an oral morphine equivalent dose.
Adverse Events
In this study, medical cannabis was not associated with any serious adverse effects, though a number of participants did report mild side effects such as dry mouth, increased appetite, and drowsiness. However, the frequency at which these side effects were experienced was not significantly increased from baseline
The reported frequencies of feelings of some symptoms such as anxiety, headaches, fatigue, and nausea actually decreased when compared with baseline. This may support the possibility that medical cannabis can be helpful in reducing these symptoms. However, the reduction in these symptoms may also be related to the reduction or discontinuation of other medications and/or the replacement of uncontrolled cannabis obtained through illicit means with regulated medicinal cannabis products.
Conclusion
The researchers of this study maintain that the data collected in this study supports the utilisation of medicinal cannabis within the context of chronic pain for the relief of pain and improvement of quality of life. It may also have a role in reducing opioid prescribing. However, they conclude that longer-term studies and registries will help evaluate the long-term prescription of medicinal cannabis for chronic pain.
