A four-year study suggests medicinal cannabis is not as effective at relieving chronic non-cancer pain as commonly assumed.
Researchers at UNSW Sydney who conducted one of the world's longest community studies of its type have found no clear role for cannabis in treating chronic non-cancer pain.
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, found that participants who were using cannabis reported over a series of assessments they were experiencing 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.
The four-year Pain and Opioids IN Treatment (POINT) study is one of the world's longest in-depth community studies on pharmaceutical opioids and chronic non-cancer pain. Researchers examined the effect of cannabis on participants' pain, on the extent to which pain interfered with their everyday life, and on their prescribed opioid use.
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 has been 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 have been no controlled studies of the potential "opioid sparing" effects.
For the POINT study, 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 a clear role for cannabis in treating chronic non-cancer pain was not found.
"Chronic non-cancer pain is a complex problem. For most people, there is unlikely to be a single effective treatment," said lead author Dr. Gabrielle Campbell.
"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."
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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Gabrielle Campbell et al. Effect of cannabis use in people with chronic non-cancer pain prescribed opioids: findings from a 4-year prospective cohort study, The Lancet Public Health (2018). DOI: 10.1016/S2468-2667(18)30110-5