Drinking coffee halves suicide risk: study

Drinking several cups of coffee daily may reduce the risk of suicide by about 50 per cent, a new Harvard study has found.
Researchers at the Harvard School of Public Health (HSPH) said caffeine plays an important role on brain chemicals.
"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.
The authors reviewed data from three large US studies and found that the risk of suicide for adults who drank two to four cups of caffeinated coffee per day was about half that of those who drank decaffeinated coffee or very little or no coffee.

Caffeine not only stimulates the central nervous system but may act as a mild antidepressant by boosting production of certain neurotransmitters in the brain, including serotonin, dopamine, and noradrenaline, researchers said.
This could explain the lower risk of depression among coffee drinkers that had been found in past epidemiological studies, the said.

Researchers examined data on 43,599 men enrolled in the Health Professionals Follow-Up Study (HPFS) (1988-2008), 73,820 women in the Nurses' Health Study (NHS) (1992-2008), and 91,005 women in the Nurses' Health Study II (NHSII) (1993-2007).
Caffeine, coffee, and decaffeinated coffee intake was assessed every four years by questionnaires. Caffeine consumption was calculated from coffee and other sources, including tea, caffeinated soft drinks, and chocolate.

However, coffee was the major caffeine source - 80 per cent for NHS, 71 per cent for NHS II, and 79 per cent for HPFS. Among the participants in the three studies, there were 277 deaths from suicide.
In spite of the findings, the authors do not recommend that depressed adults increase caffeine consumption, because most individuals 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," researchers said.

The researchers did not observe any major difference in risk between those who drank two to three cups of coffee per day and those who had four or more cups a day, most likely due to the small number of suicide cases in these categories.
However, in a previous HSPH coffee-depression study the investigators observed a maximal effect among those who drank four or more cups per day.
The study was published in The World Journal of Biological Psychiatry.