London, July 27  A study has suggested having two to four cups of coffee every day can reduce the risk of suicide among men and women by 50 per cent.

The finding was reached after researchers from the Harvard School of Public Health reviewed data from three previous US studies.

They found that the risk of suicide amongst adults, drinking several cups of caffeinated coffee on a daily basis, was about half compared to those who drank decaffeinated coffee, very little coffee or no coffee at all, Daily Mail reported.

The study, of 200,000 men and women, examined data which outlined their caffeine consumption both coffee and non-coffee sources - including tea, caffeinated soft drinks, and chocolate.

Unlike previous investigations, said lead researcher Michel Lucas, "we were able to assess association of consumption of caffeinated and non-caffeinated beverages."

".. and we identify caffeine as the most likely candidate of any putative protective effect of coffee," the research fellow in the Department of Nutrition at Harvard School of Public Health added.

Caffeine works by stimulating the central nervous system but may act as a mild antidepressant by increasing production of certain "feel good" neurotransmitters in the brain, including serotonin, dopamine, and noradrenaline.

The researchers reported this could explain why earlier epidemiological studies have found a lower risk of depression among coffee drinkers in the past.

The authors, in spite of the findings, have not recommended that depressed adults self-medicate by increasing their caffeine consumption as an increase could result in unpleasant side effects.

(IANS)