Scientists have confirmed that people who take regular exercise are less likely to be depressed, provided the activity is carried out in leisure time. However, people who exert themselves at work, for instance by digging up roads or heavy lifting, were no less likely to suffer depression than those in sedentary desk jobs.

Researchers from the Institute of Psychiatry, King's College London teamed up with colleagues in Norway to carry out the study of 40,401 Norwegian residents. Participants were asked how often they engaged in both light and intense physical activity during their leisure time. People were also asked how physically active they were at work. All the volunteers were given a physical examination and answered questions aimed at assessing their levels of depression and anxiety.

The study found that individuals who took part in regular physical activity – however mild or intense – were less likely to have symptoms of depression. However, this only held true when activity was part of leisure. Those who were not active in their leisure time were almost twice as likely to suffer symptoms of depression as the most active individuals.

Lead researcher Samuel Harvey said: "We also found that the context in which activity takes place is vital and that the social benefits associated with exercise, like increased numbers of friends and social support, are more important in understanding how exercise may be linked to improved mental health than any biological markers of fitness.