'Positive and extensive media attention' might affect outcomes of cannabis trials

In double-blind, placebo-controlled cannabinoid trials, placebo was significantly associated with pain reduction. Still, the trials received positive media attention, which researchers said could shape the results of future cannabinoid trials.

“We see that cannabis studies are often described in positive terms in the media regardless of their results,” Filip Gedin, PhD, of the department of clinical neuroscience at Karolinska Institutet in Stockholm, Sweden, said in a press release. “This is problematic and can influence expectations when it comes to the effects of cannabis therapy on pain. The greater the benefit a treatment is assumed to have, the more potential harms can be tolerated.”

Gedin and colleagues conducted the systematic review and meta-analysis to better understand placebo effect sizes in randomized clinical trials where cannabinoids were studied for pain treatment and how the trial outcomes compared with media attention. They analyzed 20 trials that included 1,459 individuals with pain. About 56% of the participants were women, and all were aged 39 to 62 years.

The researchers were primarily interested in changes in self-reported pain intensity before and after treatment, measured with either a visual or numeric scale. They also measured media presence through Almetric, a way of examining mentions in the media.

The researchers found that, after treatment with placebo, pain was rated as significantly less intense after treatment, “with a moderate to large effect size.” However, there was no difference in pain reduction between placebo and cannabis.

Gedin and colleagues also saw greater placebo responses in trials with low risk for bias (P = .02), and that “the amount of media attention and dissemination linked to each trial was proportionally high, with a strong positive bias, but was not associated with the clinical outcomes.”

“There is a distinct and clinically relevant placebo response in studies of cannabis for pain,” Gedin said in the release.

The media analysis included 136 news items that the researchers categorized as positive, negative or neutral, depending on how the item presented study results.

In all, they found that, compared with other published studies, cannabis studies garnered much greater media attention. Regardless of placebo response or cannabis’s effects, Gedin and colleagues noted that coverage was substantial and that there was no connection between a study’s positive effects and the proportion of positive news.

“In particular, we found that news articles and blogs had a strong positive bias toward the efficacy of cannabinoids in pain therapy. The positive media attention on cannabinoids for pain relief could partly explain the placebo responses seen in this systematic review,” they wrote. “Studies show that reports in the mass media and lay press and information obtained from the internet foster treatment expectations. The positive and extensive media attention may shape placebo responses in subsequent clinical trials.”

The researchers concluded that “the positive media attention and wide dissemination may uphold high expectations and shape placebo responses in future trials,” which could impact outcomes of clinical trials, clinical practice, regulatory decisions and “ultimately, patient access to cannabinoids for pain relief.”

“The data ... suggest that placebo responses contribute significantly to the pain reduction seen in cannabinoid randomized clinical trials,” they wrote. “The size of the improvements in the placebo group was moderate to high and represents clinically relevant pain relief. In line with a recent meta-analysis that compared the superiority of cannabinoids vs placebo, our analysis did not yield a significant difference between genuine drug and placebo outcomes.”

References:

• Gedin F, et al. JAMA Netw Open. 2022;doi: 10.1001/jamanetworkopen.2022.43848.
• Positive media coverage of cannabis studies regardless of therapeutic effect. https://www.eurekalert.org/news-releases/972401. Published Nov. 28, 2022. Accessed Dec. 8, 2022.