Use of illicit cannabis does not reduce chronic pain, according to new Australian study

Neelima Choahan

6/07/2018 11:02:38 AM

An Australian study has found no strong evidence that using illicit cannabis reduces pain or use of opioids in people living with chronic non-cancer pain.

New research found those taking illicit cannabis for chronic pain showed no significant improvement. (Image: Michael Fischer)
New research found those taking illicit cannabis for chronic pain showed no significant improvement. (Image: Michael Fischer)

Cannabis does not reduce pain or opioid use in people living with chronic non-cancer pain, a University of New South Wales (UNSW) study has found. 
However, the study’s participants only had access to illicit cannabis and were not taking cannabis as part of structured pain management under medical supervision, researchers say.
The medicinal use and supply of cannabis and cannabinoids was decriminalised in Australia in 2016, leading the way for increased use.
Researchers at the UNSW Sydney examined the effect of cannabis on 1500 Australians who were already part of research on treating pain through prescription opioids.
Published in The Lancet Public Health, ‘Effect of cannabis use in people with chronic non-cancer pain prescribed opioids: findings from a 4-year prospective cohort study’ is said to be one of the longest in-depth studies on people with non-cancer pain.
The study tracked the effect of cannabis on participants’ pain, the extent to which the pain interfered with their life, and their prescribed opioid use.
Professor Michael Farrell, director of the National Drug and Alcohol Research Centre and an author on the paper, told newsGP the participants’ interest in cannabis use rose from 30–60% over the course of the study.
However, the study had its limitations, he said.
‘They have not used pharmaceutical-grade cannabinoids, they have used available street-market cannabis, so one needs to be cautious about that,’ Professor Farrell said.
‘This is only one small part of the jigsaw puzzle. We are not saying this is a definitive study; there is a need for experimental studies.
‘But I do think the message of moderating people’s expectations around the type of gains they might get from [cannabis] is important.
‘Particularly for people who have no previous exposure to cannabinoids, rather than being strongly encouraged to do it, I think they should approach it with caution.’
The study showed participants who were using illicit cannabis experienced more 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.
‘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,’  lead author Dr Gabrielle Campbell said.
However, participants who used cannabis felt it worked to reduce pain, despite scoring higher levels of pain. Researchers say cannabis’ ability to improve sleep and therefore wellbeing might be one of the reasons for their belief.
‘The subjective appraisal of their pain has improved, but the more objective rating hasn’t,’ Professor Farrell said.
Researchers say a high quality, double-blind randomised placebo-controlled clinical trials are needed to better understand this complicated issue.
‘Chronic non-cancer pain is a complex problem. For most people, there is unlikely to be a single effective treatment,’ Dr Campbell said.
Associate Professor Vicki Kotsirilos, who is one of the first GPs in Australia authorised to prescribe medicinal cannabis, told newsGP the research does not focus on the use of medicinal cannabis and lacks necessary detail.
‘Often illicit cannabis is confused with medicinal cannabis,’ Associate Professor Kotsirilos said. ‘This is where the argument is often blurred and confused.’
‘This [study] is about participants using recreational illicit-produced cannabis combined with opiate medication for chronic pain management and, though useful, the research needed to ask more questions.
‘They asked about frequency of use of cannabis, but they didn’t ask what the quantity of cannabis used by each individual was, and in what form it was taken.
‘They haven’t asked about the concentration of use and what strains of cannabis was taken. Some strains of cannabis have much higher levels of THC [tetrahydrocannabinol] – the psycho-active component of cannabis.
‘They haven’t even explored how it was taken. We don’t know whether it was smoked and/or consumed in food such as cookies.
‘Illicit marijuana is different to medicinal cannabis, [the latter of] which contains much smaller doses of particular ratios of THC:CBD [cannabidiol], usually mixed in an oil or prepared as a nasomucosal spray.’
From her clinical experience, Associate Professor Kotsirilos has found those patients who were already prescribed opioids and were taking higher doses of illicit cannabis often did not respond well to medicinal cannabis. Opioids are a stronger analgesic, but cause problems with dependency and are associated with a number of risks, she said.
‘Chronic pain is a complex area,’ Associate Professor Kotsirilos said. ‘There are multiple factors that contribute to chronic pain and it can include psycho-social reasons. It needs a multi-disciplinary approach.’
Associate Professor Kotsirilos said studies clearly demonstrate social cannabis use is harmful for health and she does not support it.
However, she said, medicinal cannabis may have a therapeutic effect when used by patients with chronic pain who had never used opioids or social cannabis because they have not developed a tolerance to the higher doses of THC in cannabis or to the opioids, and are more likely to respond to smaller doses of medicinal cannabis.
Furthermore, according to Associate Professor Kotsirilos, contrary to the findings of the UNSW study, another study published in the European Journal of Internal Medicine found a reduction in the use of prescription medicine and opioid medication in the elderly when they used medicinal cannabis, not recreational cannabis.
‘Clearly more research is required,’ she said.

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