SOLNA, Sweden — Marijuana appears to have the same pain-relieving effect as a placebo — or fake pill. However, researchers say media outlets continue to cover these medical trials about cannabis-based therapies positively, regardless of the outcomes.

The findings come from a review of 20 clinical studies which examined the pain-relieving benefits of using marijuana involving more than 1,500 participants. Although previous studies have claimed that cannabis may help patients manage chronic pain, researchers from the Karolinska Institutet in Sweden found that those taking placebos experienced the same level of pain relief as those consuming active cannabinoid substances.

“We see that cannabis studies are often described in positive terms in the media regardless of their results,” says the study’s first author Filip Gedin, a postdoc researcher at the Department of Clinical Neuroscience, in a university 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.”

Study authors note that all of these trials compared cannabis use with a placebo for the treatment of clinical pain. Scientists measured the change in pain intensity before and after treatment in each trial.

Specifically, researchers found that participants said their pain dropped significantly after taking a placebo. However, there was no difference in pain reduction between those using cannabis and those consuming the fake medication.

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

The media keeps covering these marijuana trials positively — even if they fail

Study authors also looked at the connection between the pain-relieving effects discovered in these trials and the amount of media coverage they receive. Overall, the team discovered that medical trials involving marijuana generally receive more coverage and more positive reporting — regardless of how successful they really are.

The team used Altmetric to measure media presence — a system which evaluates mentions in the news, in blogs, or on social media. Researchers included 136 separate news items in their study, categorizing them as either positive, negative, or neutral. They determined each news report’s slant by examining how the results of the studies were presented based on the effectiveness of cannabis as a pain reliever.

Results show that cannabis studies received much greater media attention in comparison to other published reports. This coverage was significant even if the study found a minimal benefit from using marijuana to treat pain.

Study authors note that their review combined trials with varying designs and different levels of quality results. With that in mind, they say their findings should be interpreted with caution.

The study is published in JAMA Network Open.