Medicinal cannabis to manage chronic pain? We don’t have evidence it works
Michael Vagg is currently the Dean of the Faculty of Pain Medicine, Australian and New Zealand College of Anaesthetists. In the last 5 years, payments from pharmaceutical companies for providing educational talks to medical practitioners or other honoraria have constituted less than 0.05% of his gross income. No advisory or marketing advice has been given to the pharmaceutical industry in that time. NPS Medicinewise has paid A/Prof Vagg for consultative services to develop educational materials regarding prescription of pain medications.
Deakin University provides funding as a member of The Conversation AU.
As a pain specialist, I often have patients asking me whether they should try medicinal cannabis. There’s a common perception it can be an effective way to manage chronic pain.
But two expert groups have recently recommended against medicinal cannabis for people suffering persistent non-cancer pain.
The International Association for the Study of Pain published a position statement last week after its presidential taskforce summarised the evidence on the topic.
And yesterday the Faculty of Pain Medicine of the Australian and New Zealand College of Anaesthetists published guidance for health practitioners in the form of a Choosing Wisely recommendation. (Choosing Wisely is an initiative of NPS Medicinewise which aims to highlight low-value health care.)
Many in the community would see this recommendation as controversial. So let’s take a look at some of the commonly held misconceptions about medicinal cannabis and chronic pain.
Myth #1: evidence shows cannabis products are effective for chronic pain
Evidence from randomised controlled trials is critically lacking when it comes to medicinal cannabis products for chronic pain.
While some studies have looked at tetrahydrocannabinol (THC, the main psychoactive component of cannabis) or a combination of THC and cannabidiol (CBD), there isn’t a single published randomised controlled trial of a CBD-only product for chronic pain of any type. Australian medicinal cannabis products are often CBD-only.
This means we can’t even judge whether the claims that medicinal cannabis can alleviate pain might be true. The results of THC-containing products in clinical trials don’t give a reliable picture one way or the other because they involve too few participants, have major technical flaws in design, or have been judged to have an unacceptably high risk of producing biased results.
The International Association for the Study of Pain taskforce looked at all the available research published in peer-reviewed journals on the use of medicinal cannabis for pain management, from preclinical studies to human trials.
They concluded overall the studies’ “quality, rigour, and transparency of reporting” of benefits and harms needs to be improved across the board. We would require higher quality data, for example through randomised controlled trials, to determine the safety and efficacy of using medicinal cannabis for pain.
In the polite and understated world of academic medicine, this is about as big a smackdown as it gets. The authors are essentially saying most of the studies are too poorly done, using unsuitable methods, to give any answer to the most basic question of whether medicinal cannabis helps with pain.
Myth #2: cannabis products should be provided as a ‘last resort’
A doctor has the right to prescribe any drug they think may be effective for an individual patient based on nothing more than their clinical judgement. We do this relatively frequently, especially for chronic pain.
This is ethical if we have a scientific reason to believe the drug may be helpful. But for patients with chronic pain, we have little reason to believe medicinal cannabis offers any sustained benefit.
A further challenge to the ethical provision of cannabis products as a “last resort” is the fact they’re among the most expensive pharmaceutical products available to chronic pain patients, many of whom have very modest incomes. The only party likely to benefit is the manufacturer.
Myth #3: medical cannabis may help with the opioid crisis
There’s a consensus that much of the current use of opioid analgesics to manage chronic non-cancer pain in Australia may be of limited value.
Proponents of medicinal cannabis have suggested it may hold promise as a potential solution to this problem. While this idea has some appeal, the balance of the evidence points the other way.
Data collected from Australia and New Zealand shows participation in best-practice multidisciplinary pain care, as provided by a specialist pain clinic, results in half of pain patients being able to reduce their opioids by at least 50%, with improved quality of life.
People wanting an alternative to opioid treatment for persistent pain will do best if they seek out treatment from a professional team of experts, rather than substituting cannabis for opioids.
It could be harmful
The International Association for the Study of Pain taskforce identified general known risks from using cannabis, such as in recreational settings. But no studies have characterised the way the body handles prescribed or over-the-counter medicinal cannabis products.
The TGA guidance document on medicinal cannabis notes basic research on how the drugs interact with both the body and other medications — known as pharmacokinetic and pharmacodynamic studies — is not available. Without this information, we can’t answer important questions about the safety of medicinal cannabis.
Medicinal cannabis products may have a role in the management of other conditions, such as relieving chemotherapy-induced nausea, or treating childhood epilepsy. The evidence around those conditions seems to be more convincing than the studies for persistent pain, though I’m not an expert in either field.
Despite the lack of evidence to support the use of medicinal cannabis for chronic pain, the legislation around medicinal cannabis in Australia continues to become more permissive.
It will be legal to sell low-dose CBD products over the counter from June this year, if they meet the very minimal requirements to be listed by the Therapeutic Goods Administration (TGA).
Meanwhile, Tasmania is set to become the last Australian state to allow GPs to prescribe medicinal cannabis from July.
The Faculty of Pain Medicine has a track record of advocacy for pain patients. We led the process that resulted in the first ever National Pain Strategy a decade ago, and were a founding partner of Painaustralia as an ongoing policy voice.
If medicinal cannabis was truly as potentially valuable as often claimed, we would be the loudest voice in favour of wider access. The weight of evidence points us away from this conclusion.
Legal Cannabis hemp oil effectively treats chronic neuropathic pain
Researchers at The University of New Mexico in a recent study examined the effectiveness of consuming hemp oil extracted from the whole Cannabis plant using a chronic neuropathic pain animal model. In the study, researchers showed that legal Cannabis hemp oil reduced mechanical pain sensitivity 10-fold for several hours in mice with chronic postoperative neuropathic pain.
Distinguished from its still largely criminally prohibited cousin, “hemp” refers to Cannabis plants with less than 0.3 percent tetrahydrocannabinol (THC) per mass. Hemp is now federally legal to produce and consume in most regions throughout the United States (U.S) as a result of the Hemp Farming Act, proposed by the U.S. Congress and signed into law by President Donald Trump in 2018.
This major breakthrough in cannabis prohibition now enables millions of Americans the ability to access a natural, effective, and relatively safe alternative option for treating chronic pain. Conventional pharmacological drugs, namely opioids, are driving the leading form of preventable deaths and conventional medical errors are the third leading cause of death in the U.S.
The University of New Mexico has conducted a series of recent studies testing the effectiveness and safety of consuming the Cannabis plant, but this is the first study measuring the therapeutic potential of legal hemp oil with low THC levels.
“Cannabis plants with low THC are still psychoactive, but tend to result in fewer psychedelic experiences, while still offering profound and often immediate relief from symptoms such as pain, anxiety, and depression,” says co-researcher, Dr. Jacob Miguel Vigil, associate professor in the UNM Psychology Department.
Using a chronic neuropathic pain model that exposes mice to post-operative neuropathic pain equivalent to several years of chronic pain in human clinical patients, the researchers were able to examine how hemp oil influences momentary pain sensitivity to the affected region. For several hours after Cannabis consumption the mice demonstrated effective pain relief, approaching the mechanical pain sensitivity of naïve control mice that did not undergo the surgical operation.
“Our lab utilizes a unique nerve injury model mimicking human neuropathic pain that has allowed demonstration of hemp’s reversal of the pain-related behavior,” said one of the lead investigators, Dr. Karin N. Westlund, Department of Anesthesiology, their article titled “The Therapeutic Effectiveness of Full Spectrum Hemp Oil Using a Chronic Neuropathic Pain Model,” published in the journal Life.
Studies in animals can be superior to clinical trials because they circumvent human biases and expectancy effects, or perceptual and cognitive reactions to enrollment in cannabis-themed experiments. Several studies measuring the effects of cannabis in humans observe patients reporting psychedelic experiences, whether or not they received the active cannabis agent, otherwise referred to as the ‘placebo effect.’
The study examined the effectiveness of “LyFeBaak” hemp oil, produced by Organic-Energetic Solutions, which has been available for legal purchase in New Mexico since 2019. “We grow hemp that is optimized to potentiate the plant's utmost health and vitality through hypermineralization techniques, rather than merely plants that are grown in a state of fight-or-flight, which unfortunately is common in the cannabis industry. These techniques have enabled us to produce hemp products that patients swear are effective in treating dozens of mental and physical health conditions. The new changes in hemp laws are now allowing us to test these claims,” adds co-author and hemp grower, Anthony L. Ortiz.
“Hemp plants contain numerous therapeutic constituents that likely contribute to analgesic responses, including terpenes and flavonoids, which in theory, work together like members of a symphony, often described as the entourage effect,” says fellow researcher, Jegason P. Diviant. Several clinical investigations have shown that medications based on synthetic cannabis analogs and isolated compounds tend to offer lower reported symptom relief and a greater number of negative side effects as compared to the whole plant, or “full-spectrum” Cannabis flower and plant-based extracts.
The authors do caution that few studies exist on the long-term use of hemp oil, due mostly to historical federal prohibition laws in the U.S. “However, this is an extremely exciting time in modern medical discovery, because the average citizen now has legal access to a completely natural and effective medication that can be easily and cheaply produced, simply by sticking a seed in the ground and caring for it as you would any other important part of your life,” says Vigil.
This investigation was supported in part by private donations from individuals to The University of New Mexico Medical Cannabis Research.