Many studies have linked higher levels of physical activity with reduced depression rates, but is it the physical activity that reduces depression risks, or the depression that reduces physical activity levels? A new study may have just found the answer.

Physical Activity And Depression

By looking at hundreds of thousands of genetic data, researchers found that people with higher levels of physical activity actually had lower risks of developing depression. In fact, the researchers found that any activity is better than no activity at all, and that replacing sedentary time with 15 minutes of vigorous physical activity each day can actually cut depression risk by about 26 percent.

Genetic Approach

For the study, researchers used Mendelian randomization, in which gene variants were used to study the effects of a non-genetic factor such as physical activity. By doing so, the researchers were able to take a less biased approach to looking at the relationship between physical activity and depression. Furthermore, it can also see the exact relationship between the two factors, thereby determining which of the two actually affects the other.

For physical activity, participants either had to report on their physical activity or wear an accelerometer to measure it, and the results showed that accelerometer-based physical activities protects against depression risk. This was possibly because of inaccuracies in the report of those who self-reported their physical activity, whereas those who used accelerometers had more objective readings.

Cause And Effect Relationship

The results show that, indeed, higher levels of physical activity may causally reduce depression risks. Researchers also found no causal relationship in the other direction between physical activity and depression.

According to researchers, their findings show the importance of objective measurement of physical activity in studies regarding mental health, and in support of physical activity as an effective strategy against depression.

“Knowing whether an associated factor actually causes an outcome is important, because we want to invest in preventive strategies that really work,” said lead author Karmel Choi, PhD.

The study is published in JAMA Psychiatry.

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