Women who had two to three cups of coffee a day had about a 15% lower risk of developing depression during a 10-year period than women who had only one cup of coffee or less per week. Consuming four or more cups a day reduced the risk of depression even more, by 20%.
The study, by Harvard University researchers, analyzed health data of more than 50,000 women who were part of the Nurses' Health Study, a federally funded effort that has followed thousands of registered nurses for decades to assess risk factors for cancer and other diseases.
The Harvard research, published in the Archives of Internal Medicine, is believed to be the first study specifically looking at depression and caffeine consumption in women. The study was primarily funded by a grant from the National Institutes of Health.
Researchers said the study does not prove that caffeine or caffeinated coffee reduces the risk of depression, but it suggests caffeine has a "protective effect." Alberto Ascherio, one of the study's authors and a professor of epidemiology and nutrition at Harvard School of Public Health, said researchers decided to look at depression after smaller studies suggested a decreased risk of suicide among women who were regular coffee drinkers.
Depression is a chronic health problem that affects twice as many women as men. At least 20% of women develop depression at some point in their lives, the researchers said. Caffeine, most often in the form of coffee, is considered the world's most consumed central nervous system stimulant that temporarily boosts alertness and often improves people's moods.
Numerous studies previously have looked at the health effects of coffee. Scientists generally have concluded that for most adults moderate doses of caffeine, or the equivalent of about two to four cups of coffee a day, are not considered harmful. However, too much caffeine can cause insomnia, nervousness, stomach upset and a rapid heartbeat.
In the latest study, researchers in 1996 identified 50,739 women participating in the "Nurses' Health Study" who were free of depression. The average age was 63 at the study's onset. Over a 10-year period, 2,607 of the women developed depression.
Researchers measured caffeine consumption by analyzing a series of questionnaires the women completed between May 1980 and April 2004. The surveys asked about the types of coffee, tea, soda and other liquids that were consumed over the preceding 12 months. Women were also asked about their consumption of chocolate, which also contains caffeine.
Ascherio said most of the caffeine the women consumed came from regular coffee. He said researchers also looked at total caffeine consumption, including from other sources, and found results similar to those for coffee consumption. No association was found between intake of decaffeinated coffee and depression risk, he said.
From the September 28, 2011, Prepared Foods' Daily News.