A recent study by researchers at the University of New South Wales (UNSW) Sydney challenges the idea that cannabis could be effective for chronic non-cancer pain management.
Published in the July 2018 The Lancet Public Health journal, the study, titled “Effect of cannabis use in people with chronic non-cancer pain prescribed opioids: findings from a 4-year prospective cohort study,” found that participants who used cannabis experienced greater pain, were not coping as well with their pain, and had greater anxiety than those who didn’t use cannabis. The researchers also found no clear evidence that cannabis use reduced prescribed opioid use.
However, the researchers also found inconsistencies between their statistical assessment and what participants reported. The participants who used cannabis reported that the mean effectiveness of cannabis on pain was seven out of a possible score of 10.
“Chronic non-cancer pain is a complex problem. For most people, there is unlikely to be a single effective treatment,” said lead author Gabrielle Campbell in a UNSW Sydney press release. “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.”
Participants were recruited through community pharmacies throughout Australia for the Pain and Opioids In Treatment study, which was observed in participants with chronic non-cancer pain prescribed opioids. The participants completed baseline interviews and had follow-ups with phone interviews or self-completed questionnaires annually for four years. Recruitment took place from Aug. 13, 2012, to April 8, 2014, with 1,514 participants that completed the baseline interviews and were included in the study from Aug. 20, 2012, to April 14, 2014.
The most common types of pain reported at baseline were back or neck pain, followed by arthritis.
The study, led by the National Drug and Alcohol Research Centre (NDARC) at UNSW Sydney, was funded by the National Health and Medical Research Council and the Australian government.
According to the researchers, “this is one of the longest, in-depth, prospective studies of a community cohort of people with chronic non-cancer pain, examining the effects of cannabis use on pain and prescribed opioid use.”
Though Australia legalized medical marijuana in 2016, the change didn’t really affect the study – meaning participants mainly used illegally produced cannabis.
Some experts expressed reservations about the study.
“This study is certainly concerning regarding the efficacy of cannabis for non-cancer pain,” Dr. Jordan Tishler, a Massachusetts-area physician, president of the Association of Cannabis Specialists and CEO of inhaleMD, told Marijuana.com. “It was well-designed and had a reasonable number of subjects observed over a reasonable length of time. However, this is a prospective cohort study which can show strong relationships but cannot prove causality. In fact, in their discussion they comment on other studies, randomized controlled studies – the only kind that can show causality – that have shown benefit for pain. Their take is that those studies were too narrow in their inclusion criteria – a valid criticism – but not one that validates their own study further.”
Tishler added that though one of the major conclusions was that the cannabis users had worse pain and felt more anxiety than non-users, it’s possible – which the researchers note – that the cannabis users had worse pain at baseline and so were interested in cannabis to help in addition to their opioids more so than the non-users.
“The authors note that for most of the time during their study cannabis was fully illegal in Australia,” he said. “Not only does that mean that we have no idea what sort of cannabis patients were using, it also means, more importantly, that none of these patients were being advised and followed by a cannabis physician. We know that, like all other medications, cannabis can be used improperly and can have negative outcomes. Only with careful dosing and monitoring can we reasonably expect benefit across a broad group. This study did not attempt to stratify patients by their dose or regimen, which I would expect would have shown clear benefit to subgroups that were using cannabis in more moderate amounts.”
Tishler said he has seen benefits of medicinal cannabis in his own practice, but results can vary.
“Cannabis seems to work well for a range of non-cancer type pain: inflammatory pain like [rheumatoid arthritis]or Crohn’s, [as]well as mechanical pain like osteoarthritis,” he said. “It simply isn’t perfect. It doesn’t seem to work for everyone, and there are risks and side effects like all meds. Some people tolerate it and do well, others occasionally don’t. Ultimately we have to regard cannabis as a medicine in a dispassionate manner so that we can use it appropriately for patients.”
Osteopathic Dr. Michelle Weiner, pain management physician at South Florida’s Spine and Wellness Centers of America, said she isn’t impressed with the study and finds it is difficult to reference when her daily clinical experience finds cannabis a safer, more effective solution to decrease opioid use for pain.
“The author glazes over the fact that 22 percent and 30 percent of the patients reported that they sometimes or regularly reduced their opioid medication when using cannabis at three-year and four-year follow-up respectively,” she said.
Dr. Blake Pearson, a practicing physician specializing in cannabinoid medicine in Ontario, Canada, and founder of GreenlyMed.com, said based on the study design and methods, a significant causal relationship between cannabis use and its effects on non-cancer chronic pain can’t be established.
“This study did not investigate modes of ingestion, how much cannabis in grams was consumed, the formulation – amount and ratio of CBD or THC present – or track frequency of dosing per day,” said Pearson. “Not only that, but none of the study participants were under medical supervision for cannabis therapy. At the time this study took place, medical cannabis was still illegal in Australia, so these participants were using illegal street cannabis and would be considered “recreational users.” This is important for a number of reasons, among them, that cannabis used for recreational purposes generally does not contain CBD – the cannabinoid that is effective for pain relief without causing impairment.”
He said more studies are essential.
“Until we have more prospective, randomized controlled trials – the gold-standard in medical research – we will continue to go around in circles with the cannabis as medicine debate,” he said. “To legitimize cannabis as medicine and improve access for patients around the world who could benefit, more quality research is imperative.”