Just 20 minutes of housework or gardening a week can act as anti depressants according to a study published in the British Journal of Sports Medicine.

The more strenuous and frequent the activity, the greater the effect in lifting one’s spirits, the study found.

University College London researchers looked at a survey of 19,842 men and women taking part in the Scottish Health Survey to see how much exercise and what kind of activities they did every week. They were also asked about their state of mind before and after the activities.

The findings showed that daily physical activity reduced stress levels, irrespective of age and prolonged health problems.

The more active people were, the less likely they were to be depressed. Taking part in sports at least once a week lowered stress levels by 33%, while housework, gardening and walking could cut it by as much as 20%.

However, the study made it clear that light dusting or a lazy walk to the bus stop strictly did not count as ‘active’ exercise.

The activity needed to be for at least 20 minutes at a time, and had to leave the doer breathless.

According to experts, one theory as to why activity might enhance mood is that it prevents some biological risk factors for depression, including glucose intolerance, inflammation and cardiovascular problems.

"Many studies suggest benefits for mental health from exercise, and for the first time we have been able to quantify the amount of activity which seems to make a difference," said Mark Harmer of University College London.