Does physical activity reduce depression, or does depression reduce physical activity?

It’s a quintessential chicken and egg scenario — and a question that’s plagued scientists for some time.

Now, thanks to the power of modern genomics, a new study published in JAMA Psychiatry provides the “strongest evidence” yet that exercise has a protective effect against depression.

Using the genetic data of 300,000 adults, researchers at Massachusetts General Hospital found people with higher levels of physical activity had lower odds of major depressive disorder, according to lead researcher Karmel Choi.

“We found evidence that higher levels of physical activity may causally reduce risk for depression,” Dr Choi said.

In fact, the research shows that replacing sedentary behaviour with 15 minutes of vigorous activity each day can reduce depression risk by roughly 26 per cent.

“On average, doing more physical activity appears to protect against developing depression … and any activity appears to be better than none.”

While the study showed physical activity could prevent depression, it found no evidence that being diagnosed with depression affected a person’s ability to exercise.

If your goals include staying healthy and maintaining your fitness, you might be wondering: how much exercise do you really need to do each week?

But people diagnosed with depression are still at an increased risk of reduced physical activity, according to Joseph Firth, a senior research fellow at Western Sydney University who was not involved in the study.

“It could be social factors, rather than the actual genetics of depression.

“So, it’s still worth thinking about physical activity interventions for people with depression.”

Using exercise as prevention

Dr Firth said the study provided “the strongest evidence” to date for using exercise as a potential strategy to reduce the risk of depression across the general population.

“Depression is generally regarded as an epidemic, particularly across Western societies — many countries are struggling with high rates of it,” he said.

“These findings could ultimately inform new public health schemes, which use physical activity and exercise to not only reduce the risk of physical health problems, but also to combat the mental health epidemic.”

Dr Choi said it was one thing to know that physical activity could be beneficial for preventing depression, and another to actually get people to be physically active.

“More work needs to be done to figure out how best to tailor recommendations to different kinds of people with different risk profiles,” she said.

– Olivia Willis, ABC Health & Wellbeing

Read more: New Study Offers ‘Strongest Evidence’ Yet that Exercise Helps Prevent Depression

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