Cannabis studies receive much media attention, despite significant placebo response

Studies on using cannabis as pain reductive medicine show a significant placebo response in the study groups. Yet scientific articles that show a positive clinical effect get large media coverage, regardless of the quality of the studies. Senior Lecturer William Hedley Thompson now aims at studying how the media coverage of placebo studies can affect our expectations from a more general perspective.

Porträtt av William Hedley Thompson
William Hedley Thompson
Photo: Agnes Ekstrand

William Hedley Thompson is the co-writer of an article that is based on a meta-analysis of 20 studies of 1459 individuals participating in clinical trials, looking at the medical pain reductive effect of cannabis. 

The study behind the article unfolded two insights. One is the considerable amount of placebo response in the study groups and the other one is the way in which media covered the content of the scientific articles. The results of the studies would be presented in a positive way, regardless of the actual results and quality of the studies.

“What we decided to look at was which studies are getting attention and how much. Did the studies that seemed to have the least amount of bias get the most attention? Or the ones that had the highest clinical effect, the ones who seemed to be the most effective of treating, did they get the most attention? What we found was that there was absolutely no correlation with this.”

What possible impact could come from the media coverage?

“Part of the placebo response is expectation. You expect that this medicine that you are taking is going to work, so the placebo response is basically the expectation of something working leads to it working.”

The research team at Karolinska Institutet that William Hedley Thompson was a member of when conducting the study could see indications of a possible impact on the placebo response in future studies. The reason is that a stream of news stories with a positive undertone might lead to greater expectations that cannabis is a good treatment for chronic pain. 

“We haven’t got that final part of the puzzle; we haven’t proven that the placebo response is caused by the media, but at least we found that the media has a possibility of increasing the expectations due to the media coverage. That is what we found quite exciting.”

So cannabis doesn’t work as a treatment for long term pain?

“According to the studies we looked at in our meta-analysis, no. We saw that the use of cannabis to relieve pain may not be better than placebo, based on the evidence we have available today, but there could be other uses for cannabis in medical purposes. We are not excluding those possibilities.”

How was the study conducted?

One of William Hedley Thompson’s contribution to the study, was finding a way to collect data and synthesize the results.

“The research group utilized online tools to collect data about how different media writes about scientific articles. These tools are called Altmetrics. We used one which allowed us to utilize this data in quite a unique way. It’s being used in many interesting ways, but we think at least that we are the first people to use this type of data in relation to the placebo response, which we think is quite cool.”

Why can we find so much written about the positive outcome of cannabis studies?

“Why this happens is an interesting question. There is obviously a lot of interest regarding cannabis in general in multiple countries, where there is a lot of decriminalization for recreational use and medical applications as well.”

William Hedley Thompson states that when a subject is hyped in general, it will generate a lot of media coverage.

“A consequence of hype in any type of clinical trial, could be the media covers the results regardless of the clinical effect and can therefore also increase the placebo response. So this could be a more general effect and that is actually something we are looking to do in the future, to see if this is a more general thing or a cannabis specific topic.”

The article William Hedley Thompson is the co-writer of was published in JAMA Network Open.


Text: Agnes Ekstrand