Study supports physical activity as a preventive measure for depression

By Sarah MooreNov 5 2019

A new study has found that physical activity may have a preventative effect against depression. Physical activity has long been linked with better mental health due to its ability to reduce the stress hormone cortisol and increase the feel-good hormone serotonin.

However, there has been limited empirical evidence to support physical activity as a preventive measure for depression, making these findings very important.

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Physical activity can reduce depression

Karmel Choi, at the Psychiatric and Neurodevelopmental Genetics Unit in the MGH Center for Genomic Medicine, led a team in investigating the potential preventative effect of exercise on depression.

The team used genetic data to uncover evidence supporting the idea that increased engagement in physical activity has the effect of reducing depression, and that the relationship is causative rather than merely correlational. Finding a causal relationship is key because it provides information on what preventative strategies could help those with depression.

A causative relationship

The study relied on the use of the Mendelian randomization technique, where gene variants are used to investigate the impact of a non-genetic factor. The technique uses the gene variants as a form of a natural experiment; in this study, they looked at gene variants in relation to higher or lower average levels of physical activity.

Due to the fact that genetic variants are inherited randomly, they are able to provide a robust method of identifying a true relationship between physical activity and depression. The technique can also be used to identify whether a relationship is actually causative and say which factor is impacting the other. In this case, they found that physical activity was able to impact the incidence of depression.

The team used the findings of large-scale genome-wide association studies (GWAS) to identify gene variants related to physical activity and to depression. Researchers had two measures of physical activity available to them from the GWAS results, one based on self-reports of activity, and one based on accelerometer readings.

For depression, the GWAS was based on data collected from over 143,000 individuals both with and without the disorder. The results found that the accelerometer-based physical activity was successful in preventing depression, but self-reported activity was not. This is likely due to limits in the accuracy and reliability of the self-report method.

How much exercise is required to prevent depression

The researchers explained that there was no specific level of physical activity that was required to bring the benefits of depression prevention. They highlight that the results suggest that any level of activity is better than none. Just 15 minutes of vigorous activity or an hour of moderate activity was sufficient to lower depression risk.

Take-home message

While the study has uncovered the causative relationship between physical activity and depression, supporting that physical activity can be used as a preventative method to protect against the mood disorder, it is only part of the journey towards developing effective new treatment methods.

What must be explored next is how to get at-risk people to become more physically active: what techniques can encourage engagement in physical activity consistently and on a long term basis? The next step is to look into how to tailor treatment offerings to ensure that people with different individual needs and risk profiles are catered for.

Overall, these findings open up the possibility of physical activity becoming prescribed in some form by GPs treating people with depression or at-risk of it. This could potentially lead to a reduction in reliance on pharmaceutical drugs which can have significant unwanted side effects.