Just five minutes of exercise in a green environment - like a park, back garden or nature trail – can boost mental health, according to a new study.

The research, published in the American Chemical Society’s Environmental Science & Technology journal, says there is “abundant scientific evidence” that activity in natural areas decreases the risk of mental illness and improves the sense of wellbeing, but until now, it wasn’t known how long people had to spend in green spaces to achieve those benefits.

Jules Pretty, one of the authors (alongside Jo Barton), said: “For the first time in the scientific literature, we have been able to show dose-response relationships for the positive effects of nature on human mental health.”

From an analysis of 1,252 people of different ages, genders and mental health status, drawn from 10 existing studies in the UK, the authors were able to show that activity in the presence of nature led to mental and physical health improvements.

They analysed activities such as walking, gardening, cycling, fishing, boating, horse-riding and farming. The greatest health changes occurred in the young and the mentally-ill, although people of all ages and social groups benefited. All natural environments were beneficial including parks in urban settings. Green areas with water added something extra. A blue and green environment seems even better for health, Pretty noted.

From a health policy perspective, the largest positive effect on self-esteem came from a five-minute dose.

"We know from the literature that short term mental health improvements are protective of long term health benefits," Pretty said. "So we believe that there would be a large potential benefit to individuals, society and to the costs of the health service if all groups of people were to self-medicate more with green exercise," added Barton.