A study published in JAMA Psychiatry analysed data from 15 studies of 191,130 adults who were followed for at least three years.
Rates of depression and the physical activity levels of the participants were tracked. Researchers compared those who were recommended 150 minute a week of moderate-intensity exercise to those who did not achieve that amount.
The results found those who exercised for at least 150 minutes a week had a 25 per cent lower risk of depression than those who did not exercise for all long.
The risk of depression for those who only achieved half the recommended amount of exercise lowed to just 18 per cent.
The findings “suggests significant mental health benefits from being physically active, even at levels below the public health recommendations,” the researchers concluded in the study.
“Health practitioners should therefore encourage any increase in physical activity to improve mental health.”
The study did not analyse why exercise may help prevent depression.