A new study has demonstrated that people who are physically active three times a week are less likely to go under depression.

The study conducted at University College London (UCL) showed that people who increased their weekly activity reported fewer depressive symptoms but those with more depressive symptoms were less active, particularly at younger ages.

Researchers followed 11,135 people born in 1958 up until the age of 50, recording depressive symptoms and levels of physical activity at regular intervals in adulthood. They found that each additional activity session per week reduced odds of depression by 6 percent. In England 19 percent of men and 26 percent of women were currently classed as "inactive', and this study suggested that activity could significantly improve their mental as well as physical health.

Dr Snehal Pinto Pereira of the UCL Institute of Child Health, lead author of the study, said that assuming the association was causal, leisure time physical activity had a protective effect against depression. If an adult between their twenties and forties who was not physically active became active 3 times per week, they would reduce their risk of depression by approximately 16percent.

The study showed that people who reported more depressive symptoms at age 23 tended to be less physically active, but this effect weakened as they grew older.

Professor Mark Petticrew of the London School of Hygiene and Tropical Medicine, Director of the Public Health Research Consortium, said that many people were already aware of the benefits of physical activity on their general health, but they were now seeing a growing body of evidence that suggested it also had a positive effect on a person's mental well-being.

The study is published in JAMA Psychiatry.