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Cannabis Products Can Relieve Chronic Pain in the Short-Term, Review Finds

By Alexander Beadle

Published: Jun 10, 2022   
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A new review of 25 studies trials has concluded that oral synthetic cannabis products with high amounts of THC can result in moderate short-term improvements in chronic pain. Similarly, extract products with comparable THC-to-CBD ratios may also provide small improvements in pain relief.

The review, published in Annals of Internal Medicine, noted that these products did come with an elevated risk of adverse events such as dizziness and sedation. Other plant-based cannabis products were found to have no significant effect on chronic pain.

The researchers say that more studies are still needed to determine the long-term effects of cannabis for chronic pain. In an accompanying editorial article, other pain experts explained that this limitation is due in part to the continued prohibition and the stigma related to cannabis products, which has tended to encourage research into cannabis-related long-term harms rather than long-term therapeutic effects.

Synthetic THC products can help to combat pain

In total, the authors from Oregon Health & Science University examined 18 randomized, placebo-controlled trials, comprising 1,740 participants, and 7 large cohort studies, comprising a further 13,095 participants.

The review found that synthetic THC products with high THC-to-CBD ratios were associated with moderate decreases in pain intensity. Cannabis extract products with roughly equal THC-to-CBD ratios were associated with small improvements to pain, but also small improvements to overall function.

The authors say that these effects are roughly on par with other treatments given to chronic pain patients, such as opioid medications. However, the total body of evidence supporting cannabis therapies is weaker.

“The average reduction in pain severity is also similar to some other treatments, but we do not have studies directly comparing these treatments to draw conclusions,” lead study author Prof Marian McDonagh said, speaking to WebMD.

Somewhat surprisingly, no significant effects on pain were seen for whole-plant cannabis or for products with low THC-to-CBD ratios. The review authors determined that this was generally down to studies that were limited by serious imprecision or other methodological limitations that made them unsuitable for studying effects on pain.

“In general, the limited amount of evidence surprised all of us,” McDonagh told the Telegraph.

“With so much buzz around cannabis-related products, and the easy availability of recreational and medical marijuana in many states, consumers and patients might assume there would be more evidence about the benefits and side effects.”

“We only saw a small group of observational cohort studies on cannabis products that would be easily available in states that allow it and these were not designed to answer the important questions on treating chronic pain,” McDonagh explained.

While it was determined that higher THC-to-CBD ratio formulations put participants at risk for dizziness, nausea, and sedation, other key adverse event outcomes such as psychosis or the development of cannabis use disorder were not routinely screened for or not reported. Broadly, studies need to do more to evaluate such potential harm outcomes, the reviewers concluded.

Doctors should meet pain patients “where they are”

As noted in the accompanying editorial, authored by Kevin F. Boehnke, PhD, and Daniel J. Clauw of the Chronic Pain and Fatigue Research Center at the University of Michigan Medical School, some physicians cite the current lack of data on cannabis for pain as a rationale for not engaging with patients who might want to try medicinal cannabis treatments.

“Such practices may reflect consideration of cannabis solely as a drug of misuse (even in the 37 states where medical cannabis is legal) and requirements to refer patients who disclose or test positive for cannabis use to addiction services or decline to refill opioid prescriptions,” Boehnke and Clauw wrote. “This stance harms the trust necessary for shared, patient-centric decision making that is already hampered by the stigma associated with cannabis use.”

Instead, Boehnke and Claw propose that clinicians act as a pragmatic source of guidance and harm reduction information. For example, if a patient is set on pursuing medical cannabis treatment, the clinician could recommend alternative administration methods such as tinctures or oral capsules, in order to limit any risks associated with smoking.

“Given the slow pace of clinical trials, we believe it likely that McDonagh and colleagues' findings will be the best available evidence for some time. While we await better evidence, we believe that clinicians should meet patients with chronic pain ‘where they are,’” they wrote.

“Conventional analgesic medications are effective only in a subset of persons, so it is no wonder that many patients are drawn to widely available cannabis products. Clinicians can compassionately witness, record, and offer guidance to help patients with chronic pain use cannabis wisely.”

Cannabis for chronic pain

As exemplified in the new review, the evidence base supporting cannabis as a treatment for chronic pain is rather mixed and can vary greatly depending on the cannabis products offered. However, even small improvements to pain may be very important to patients.

A recent Rapid Recommendation from the British Medical Journal concluded that non-inhalable medical cannabis products should be given to people living with chronic pain, if their pain is not being effectively managed by other standard interventions.

This recommendation was informed by an expert panel of patients, clinicians, and other medical specialists, who examined numerous systematic reviews before making their “weak recommendation” in support of using cannabis for chronic pain. The recommendation is weak, they explain, as the absolute improvements in pain were generally very small but that these improvements were highly valued by patients.

This tracks with the findings of a recent survey of medical cannabis patients in Pennsylvania, who reported significant improvements in pain and health-related quality of life.

Preliminary results from Project Twenty21, Europe’s largest medical cannabis patient registry, also highlight significant improvements in patient quality of life after initiating medical cannabis treatment. The participants in Project Twenty21 are receiving cannabis for conditions including chronic pain, multiple sclerosis, epilepsy, and post-traumatic stress disorder.

Currently, the treatment guidelines set out by the National Institute for Health Care and Excellence (NICE) for patients in the UK give strong recommendations against prescribing medical cannabis for chronic pain. However, the UK Health Research Authority recently issued conditional approval for the country’s first clinical study on cannabis flower for treating chronic pain.

Dubbed “CANPAIN”, the study aims to enroll 5000 chronic pain patients, with the study conductors hoping that the results could inform future revisions to this NICE guidance. However, before the CANPAIN study gets underway, its organizers will need to first conduct a smaller feasibility study of 100 patients to examine the patients experience and solidify data collection and logistics strategies.


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