Exercising while you're young can help to prevent depression in later life, a new study has shown for the first time.

However a new study has shown that not only can light activity treat depression, it can actually prevent it.

Researchers looking at 26-years' worth of data have shown that people who exercise when they're young are less likely to become depressed as they get older.

The project, which analysed data from 30 previous studies, found that in 25 of them there was a link between lack of activity and being diagnosed with depression in later life.

George Mammen, Ph.D. candidate from the University of Toronto and co-author of the study, said: 'I'm active so I wasn't surprised to find this, but 25 out of 30 showed a significant effect and that was unexpected.'

The study, published in the American Journal of Preventive Medicine, recommends around 20-30 minutes of light activity, such as walking or gardening, every day.

Speaking to NBC News, Mammen added: 'If you're not physically active, you should start.We usually think of exercise in terms of weight and how we look, but it's also a way to maintain mental health far into the future.'

Depression affects around 1 in 5 elderly people in the UK, according to the Mental Health Foundation, with women being more likely than men to suffer from it.

According to the British Medical Journal those with depression are more likely to suffer from dementia, Parkinson's disease, chronic pain and disability, and even suffer from strokes.

They estimate that there are proportionately more suicide attempts by those aged 65 and over than any other age group, with the majority suffering from depression.

While it has long been known that exercise can be used to treat depression, the study is the first of its kind to show that it can prevent the condition from starting.