Results of a four-year study, by researchers at UNSW Sydney of over 1,500 Australians prescribed opioids for chronic non-cancer pain, suggest that there is a need for caution in the use of medicinal cannabis for chronic pain.
The use of cannabis for medicinal purposes has been increasing worldwide, and chronic non-cancer pain is the most common reason cited for medicinal use. There has been speculation that using cannabis for pain may also allow people to reduce their prescribed opioid use. To date however, long-term evidence is limited: randomised control trials of cannabis for pain typically have short durations of generally three months and tend to exclude patients with complex physical and mental health problems; and there are no controlled studies of the potential “opioid sparing” effects.
In one of the world’s longest in-depth community studies on pharmaceutical opioids and chronic non-cancer pain, the Pain and Opioids IN Treatment (POINT) study, the researchers examined the effect of cannabis on their pain, on the extent to which pain interfered with their everyday life, and on their prescribed opioid use.
In the study, funded by the National Health and Medical Research Council and led by the National Drug and Alcohol Research Centre (NDARC) at UNSW Sydney, participants were recruited through community pharmacies and completed comprehensive assessments of their pain, physical and mental health, medication and cannabis use annually. Approximately 80% of the sample completed each assessment. Participants had been in pain for a median of 10 years and taken prescribed opioids for their pain for a median of four years. There were very high rates of physical and mental health problems.
The results, published in Lancet Public Health, suggest that there is a need for caution because the findings did not find a clear role for cannabis in treating chronic pain. At each assessment, participants who were using cannabis reported greater pain and anxiety, were coping less well with their pain, and reported that pain was interfering more in their life, compared to those not using cannabis. There was no clear evidence that cannabis led to reduced pain severity or pain interference or led participants to reduce their opioid use or dose.
Interestingly, participants who used cannabis for pain reported that cannabis was effective for their pain (mean score of 7 out of 10). One possibility is that cannabis improves sleep, which in turn improves well-being. We need high-quality, double-blind randomised placebo-controlled clinical trials to better understand this complicated picture.
“Chronic non-cancer pain is a complex problem. For most people, there is unlikely to be a single effective treatment. In our study of people living with chronic non-cancer pain who were prescribed pharmaceutical opioids, despite reporting perceived benefits from cannabis use, we found no strong evidence that cannabis use reduced participants’ pain or opioid use over time,” said lead author Dr Gabrielle Campbell.
The article, Effect of cannabis use in people with chronic non-cancer pain prescribed opioids: findings from a 4-year prospective cohort study, is available online via Lancet Public Health.
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