A new study by Harvard University researchers found that coffee acts as an antidepressant among the people who consume caffeinated products on a regular basis.

The researchers studied 50,739 older women participating in the Nurses' Health Study who were free of depression and prospectively followed them for 10 years, from 1996 to 2006.

They eventually found out that the women who had two to three cups of coffee a day were at 15 per cent lower risk of developing depression than the ones who had only one cup or less coffee in a week.

Over a 10-year period, 2,607 of the women developed depression, but the women who consumed four or more cups of coffee a day were at 20 per cent reduced risk of depression.

The researchers suggest that during the 10-year study, they observed that caffeine or caffeinated products have a protective effect, and that people who consume caffeinated products on a regular basis are less likely to suffer from depression.

The authors noted that the cases of depression decreased in a dose-dependent manner with increasing consumption of caffeinated coffee.

 However, they are averse to claim any conclusion that says that caffeine reduces the risk of depression.

The latest study is said to be the first large-scale study of coffee consumption to evaluate a mental health outcome in women.

The finding of the study is published in the September issue of journal Archives of Internal Medicine.