Adults who exercise for 75 minutes a week are 18% less likely to have depression

Walking at a brisk pace for just 75 minutes every week could cut your risk of depression, a new study finds.

The World Health Organization recommends everyone should exercise for at least two-and-a-half hours every seven days.

But researchers at Cambridge University, England, found adults who got half as much were a fifth less likely to have depression, while those who did the full time had a 25 per cent reduced risk.

Scientists said it suggests even a small amount of exercise could have a ‘substantial benefit’ to someone’s mental health.

Exercise may help with depression because it triggers the release of endorphins — feel-good chemicals — and improves perception of body image, they said. 

Researchers tracked the exercise regimes of more than 190,000 people during the study, to calculate the risk of them having depression (stock image)

Depression is a major cause of disability worldwide, with sufferers battling through long periods of unhappiness and hopelessness.

About one in five American adults — or 40 million people — suffer from the condition, estimates suggest.

Some studies have suggested physical activity can help to prevent depression, and may even be as effective as anti-depressants.

In the latest meta-analysis — published in JAMA Psychiatry — researchers analyzed data from 190,000 adults, including 28,000 who had depression.

READ RELATED: The push up challenge founder Nick Hudson shares his own history with depression

The 15 studies used all monitored participants activity levels and whether they had depression for at least three years.

People who did half of the recommended amount of exercise were compared to those who did no exercise. 

The vast majority of studies used were carried out in the developed world, with six in the U.S., six in Europe, and one in both Australia and Japan.

One study was conducted in the developing world, which looked at India, Ghana, Mexico and Russia.

There was a quick reduction in rates of depression even at low activity levels, results showed.

But when participants did more activity, mood-boosting returns steadily reduced. 

In the study led by Dr Matthew Pearce, an epidemiologist, scientists noted: ‘Substantial mental health benefits can be achieved at physical activity levels even below the public health recommendations.

‘(There was) an additional benefit for meeting the minimum target, but limited extra benefit beyond that.’ 

They added: ‘Assuming causality, one in nine cases of depression might have been prevented if everybody in the population was active at the level of current health recommendations.’

The researchers said it was likely ‘more than one mechanism’ triggered by exercise was resulting in lower rates of depression.

They suggested exercise may relieve symptoms because it triggers the release of endorphins in the brain, promoting feelings of well-being.

It could also improve someone’s self-perception, body image and encourage more social interactions.

But they warned the associations could actually come down to people with depression being less likely to exercise, rather than working out having a benefit. 

‘It is still possible that the associations observed… could overestimate the role of physical activity,’ they said.

The study was observational, and could not rule out another factor causing reduced depression rates in people who exercise more.