HARVARD GAZETTE ARCHIVES
Go ahead and have that second cup of coffee, even a third or fourth cup. You may be protecting yourself against depression and suicide.
Women who drink two, three, or more cups of coffee a day are less likely to commit suicide than non-coffee drinkers, according to a Medical School study of 86,626 nurses. That rather startling conclusion comes less than a month after another study of the same women excluded coffee as a cause of heart disease.
These results apply equally to men, other research has found. For example, a check of 120,000 people in northern California showed substantially the same lowering of suicide risk for two, three, even six or more daily cups of coffee for both sexes.
"You always hear about coffee and caffeine being bad for your health," notes Ichiro Kawachi, assistant professor of medicine. "Our studies have found no basis for implicating coffee in any serious long-term health effects."
The good feeling produced by java apparently comes from caffeine's impact on the nervous system. "You would get the same advantage from the caffeine in tea or soda, but you'd have to consume gallons of these beverages to get the same effect," Kawachi says. The same would be true for decaffeinated coffee which, despite its claim, still has a small amount of the stimulant.
It takes about seven cups of tea or cans of cola to get the same "high" that you would get from two cups of regular coffee. An average cup of coffee contains about 140 milligrams of caffeine, compared to about 40 for colas like Coke and Pepsi, and 30 to 40 for tea.
Those who consume 100 to 1,000 milligrams of caffeine a day, or one to seven cups, report improvements in mood, sociability, self-confidence, energy, and motivation for work. That kind of pickup is limited to habitual coffee drinkers, however. Those who don't drink it regularly sometimes get feelings of anxiety and general ill-being.
The Harvard report notes that high coffee consumption usually is associated with smoking, drinking alcohol, and increased stress, all of which have been linked to a higher risk of suicide. "These effects may be counteracted by caffeine's elevating influence on mood," Kawachi notes. "But it's premature to recommend that all healthy adults include two to three cups of coffee daily in their diet."
The Nurses' Health Study was conducted by having them complete questionnaires over a 10-year period. Any dietary recommendation would have to be based on more conclusive studies that eliminate other possible explanations for the results.
For example, doctors may have advised depressed people, especially those taking medication, to avoid coffee. That would have skewed the results in favor of coffee drinkers, because the group most likely to commit suicide would not be drinking the beverage.
"One intriguing possibility would be a study to determine if caffeine can help prevent or ameliorate depression," Kawachi says.
The suicide study was published in the March 11 issue of Archives of Internal Medicine. The heart disease investigation was reported in the Feb. 14 Journal of the American Medical Association. The authors of both reports include researchers at the Medical School, School of Public Health, and Brigham and Women's Hospital.
Copyright 1998 President and Fellows of Harvard College