Weekend reading | Exercise as a treatment for depression: Unraveling data bias

Written by Kevin Scofield

this weekend's read Investigating the effects of exercise on people suffering from depression. Beyond prescriptions and treatments, many medical professionals suggest many alternative ways to treat depression, including dietary changes, increasing sunlight and outdoor time, and regular exercise. A group of researchers from Australia, Spain and Denmark examined around 250 previous studies on exercise and depression to try to understand what types of exercise are effective.

It turns out to be more difficult than you imagine. Most previous studies have been “pairwise” studies, comparing people in a control group to people who did a particular type of exercise, or in some cases more or less intensely. And the pair were all over the map.

To sort this out, we needed to conduct a “network meta-analysis” to uncover the larger relationships beyond the specific pairs studied. To do so, we need to infer transitive relationships. For example, if A is more effective than B, and B is more effective than C, then A is more effective than C. But it's not that simple. Think about it: If A is slightly better than B, and C is much better than B, does that mean that C is better than A? If so, How good is it in what situations?

A short summary of what they found in their meta-analysis is that exercise has a greater therapeutic effect on people with depression, in some cases than therapy or medication. Topping the list is dancing, followed by walking and jogging, and yoga, cardio, strength training, and tai chi have also shown visible results. Researchers also found that the intensity of exercise was important. The higher the intensity, the more effective the treatment.

However, there is a catch. The researchers also concluded that although there were approximately 250 studies to review, confidence in their findings was low. They spend much of their report detailing why their conclusions are less reliable, much of it due to possible bias in the way the study was conducted.

There are many potential sources of bias in the way scientific experiments are designed, conducted, and evaluated. There is also “reporting bias.” Studies with interesting results are more likely to be fully written up by researchers and submitted for publication. Similarly, there is “publication bias.” Scientific journals are more likely to publish studies with positive results than studies with negative results, even if the negative results are important. Therefore, while the published literature is full of interesting and positive results, there is little data on less interesting and negative results. Therefore, it is not possible to determine whether the published studies are truly representative of all studies conducted and their results.

Researchers looked closely at all 250 studies and found that most showed a risk of bias. It's not necessarily an actual bias, but rather a problem with the way the study was conducted, which may have introduced (yet undetected) bias. In particular, we found that very few studies were conducted completely 'blind' in that either participants, staff or outcome assessors knew what outcome they were looking for. . This tends to lead to “expectation bias” where people are more likely to find the results they are looking for.

Potential biases, as well as the fact that some forms of exercise have been poorly studied, led the researchers to conclude that the results should be treated with a low degree of confidence. They weren't proof-wise wrong, but they're more likely to be wrong. For example, dance appeared to have the greatest therapeutic value, but there were only three studies, and they were at risk of bias. In fact, dancing may be the best treatment, but we don't yet have enough solid data to conclude that.

Still, there are enough facts to suggest that medical professionals should prescribe exercise to patients suffering from depression, especially those who have not responded to treatment or medication. This is especially important because, as researchers point out, only 51% of people in high-income countries have access to traditional treatments for depression, and only 20% in low-income countries. . If exercise is an effective treatment, it is cost-effective and easy to scale up. More research is needed to understand how much exercise helps with depression (and in what ways), but this is a promising start.

Effects of exercise on depression: A systematic review and network meta-analysis of randomized controlled trials.

kevin schofield Freelance writer and published author Seattle Paper Trail.He previously worked at Microsoft and published Seattle City Council Insightsco-hosts “Seattle News, Views and Beers.” podcast, I raised two daughters as a single father. He serves on the Board of Directors of the Woodland Park Zoo and also does volunteer work.

📸 Featured Image via Mickey/Shutterstock.com.