Researchers at the Harvard School of Public Health found that drink two or more cups of coffee per day can reduce risk of suicide by up to half.
According to the study, caffeine acts as a mild antidepressant by increasing production of neurotransmitters including serotonin, dopamine and noradrenaline. The finding confirms previous studies showing an association between drinking coffee and lower risk of depression.
"Unlike previous investigations, 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," said lead researcher Michel Lucas.
Researchers analyzed the data of 43,599 men enrolled in the Health Professionals Follow Up Study (HPFS) between 1988 and 2008. They also analyzed 73,820 women who were a part of the Nurses' Health Study (NHS) conducted between 1992 and 2008 and a further 91,005 women who were a part of Nurses' Health study II (NHS II) between 1993 and 2007.
Caffeine intake was calculated not just from coffee but other sources including caffeinated soft drinks, chocolate and tea. Coffee was the primary source of caffeine, however, with 80 percent in the NHS group followed by 79 percent in NHS II and HPFS. Nearly 277 total deaths occurred due to suicide.
But study authors do not recommend depressed individuals increase their caffeine consumption. Most people naturally adjust their caffeine intake to an optimal level for them, and an increase could result in "unpleasant side effects."
"Overall, our results suggest that there is little further benefit for consumption above two to three cups/day or 400 mg of caffeine/day," Lucas wrote.