New research has indicated that four or more cups of coffee a day acts as a mood enhancer and has the potential to stave off depression in women.

Scientists from the Harvard School of Public Health in Boston tracked the health of 50,000 US female nurses between 1996 and 2006, using questionnaires to track their coffee consumption.

In a study published in the Archives of Internal Medicine, they found that those who drank one or fewer cups of caffeinated coffee per week had a 20 percent higher risk of developing clinical depression than those who consumed four cups a day. Those who consumed two to three cups per day had a 15 percent decreased risk of developing depression.

The women who drank coffee were also more likely to smoke, drink alcohol and were less involved in community groups: but even with these variables taken into account, they were much less likely to develop depression than their caffeine-low counterparts.

The researchers believe caffeine is a key element in enhancing mood and feelings of well-being; however, they cautioned that it was too early to begin recommending women to drink more coffee on that basis.

It is not yet clear how exactly caffeine performs to improve wellbeing, but it is thought it may alter the brain's chemistry.

Leading the study, Dr Michel Lucas said: "Our results support a possible protective effect of caffeine, mainly from coffee consumption, on risk of depression.

"Further investigations are needed to confirm this finding and to determine whether usual caffeinated coffee consumption may contribute to prevention or treatment of depression."

Coffee 'reduces' depression in women