Monday, November 28, 2022

Media Coverage, Placebo Response Linked to Pain Relief Seen in Cannabinoid Trials

A strong placebo response contributes significantly to the perception of pain reduction observed in clinical trials of cannabis-based therapies, according to a review and meta-analysis in JAMA Network Open. The study also suggests that media coverage of cannabis trials may promote high expectations of pain relief in clinical trial participants, thus increasing the placebo effect.

“In particular, we found that news articles and blogs had a strong positive bias toward the efficacy of cannabinoids in pain therapy,” wrote Filip Gedin, Ph.D., of Sweden’s Karolinska Institutet and colleagues. “The unusually high media attention surrounding cannabinoid trials, with positive reports irrespective of scientific results, may uphold high expectations and shape placebo responses in future trials. This influence may impact the outcome of clinical trials, regulatory decisions, clinical practice, and ultimately patient access to cannabinoids for pain relief.”

Gedin and colleagues identified 20 clinical trials that tested cannabis-based products for pain relief. The combined sample included 1,459 adults who had pain conditions such as neuropathic pain or multiple sclerosis. All participants were given placebo; tetrahydrocannabinol (THC) and/or cannabidiol (CBD) extracts; or synthetic cannabinoids like nabilone, in a variety of formats, such as pills, oils, sprays, and vapor.

Overall, participants who received an active cannabis product reported large reductions in pain intensity. However, the participants who took placebo also reported significant reduction in pain intensity, and there was no statistical difference in pain relief between the groups.

The treatment delivery method, duration of the study, or type of patient pain did not influence the size of the placebo effect. However, a larger placebo response was observed among well-controlled trials that reduced potential biases.

The authors wrote that it is possible that the trials with low risk of bias were successfully blinded so that patients could not tell whether they were receiving active cannabis. Thus, participants in the placebo group who had high expectations of pain relief were more likely to maintain positive treatment expectations through the trial and benefit more from the placebo treatment.

To read more on this topic, see the Psychiatric News article “Be Prepared to Discuss CBD Products With Patients.”

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