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EXPERT REACTION: Cannabis for pain? It's still complicated

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A US study of existing research looking at cannabinoid drugs for pain relief has found they may prevent the onset of pain by increasing pain thresholds, but may not reduce the intensity of pre-existing pain or help people who are hyper-sensitive to pain. However, the drugs may make pre-existing pain less unpleasant and more tolerable, say the researchers. They analysed 18 placebo-controlled studies, including a total of 422 participants.

Journal/conference: JAMA Psychiatry

Link to research (DOI): 10.1001/jamapsychiatry.2018.2503

Organisation/s: Syracuse University, USA

Funder: The Syracuse University STEM Fellowship, National Institute on Alcohol Abuse and Alcoholism, National Institute on Drug Abuse.

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Professor Lorimer Moseley is a professor of Clinical Neurosciences, Foundation Chair in Physiotherapy, NHMRC Principal Research Fellow and the Chair of PainAdelaide

It is a really important review mainly because it shows how little data are out there when it comes to cannabis and pain. The data that do exist seem to show that, when it comes to very short-term pain induced in a laboratory, cannabis doesn’t change pain intensity but people find the same pain less awful and therefore more tolerable. That the study involved psychoactive cannabis probably means that people knew they got the drug and were probably high - which might get explain why they were less bothered by the same amount of pain. 

Unfortunately this study tells us nothing about the potential role of cannabis in real-world pain, which is not so short-lived and has a totally different meaning. Critically, it is even further removed from persistent pain, which is what people are using it for. The lesson? Don’t take these results and apply them to persistent pain.

Last updated: 20 Sep 2018 2:52pm
Declared conflicts of interest:
None declared.
Wayne Hall is an Emeritus Professor at the National Centre for Youth Substance Use Research at the University of Queensland

This paper reports a meta-analysis of the effects of cannabinoids – predominantly containing the psychoactive ingredient tetrahydrocannabinol in the cannabis plant - on acute experimental pain in healthy young adults. Its findings suggest that THC has small to medium analgesic effects. It modestly increased pain thresholds, reduce the unpleasant aspects of pain and increased pain tolerance. It did not reduce pain intensity or produce brain changes in the way pain is perceived. 

These results are broadly consistent with systematic reviews of clinical trials of cannabinoids in treating chronic non-cancer pain, such as the pain experienced by persons with multiple sclerosis. Systematic reviews have found that cannabinoids produce a small increase in the proportion of patients who experience a reduction in their pain compared to patients who were given a placebo. For example, on average 29 per cent of chronic patients experienced a clinically significant reduction in pain when given a cannabinoid as against 25.9 per cent of those given a placebo (Campbell et al, 2018). These findings should moderate patients’ expectations about the analgesic effects of cannabinoids. Research is needed to better define the minority of chronic pain patients who will benefit from using medicinal cannabinoids. 

Last updated: 19 Sep 2018 12:15pm
Declared conflicts of interest:
None declared.

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