Sept. 26 (Bloomberg) -- Drinking caffeinated coffee may help women fight depression, Harvard researchers said, cautioning that more study is needed before they’d recommend adding several cups a day as therapy.
Women who consumed four or more cups of caffeinated coffee a day had a 20 percent decreased risk of developing depression over the 10-year period compared with those who consumed one cup or less a week, according to a study released today in the Archives of Internal Medicine. The findings applied only to coffee, which has higher levels of caffeine than teas, sugary sodas or chocolate, the researchers said.
About one in five U.S. women will be diagnosed with depression in her lifetime, the authors wrote. Today’s study is the first and largest analysis of caffeine and depression in women, author Alberto Ascherio said. The research adds to studies that have linked coffee to benefits such as a decreased risk of prostate cancer and harms such as an association with miscarriages.
“This is an observational study,” said Ascherio, professor of epidemiology and nutrition at Harvard School of Public Health in Boston, in a Sept. 23 telephone interview. “We can’t translate this into a recommendation, not at this stage.”
It’s unclear how caffeinated coffee may work in the brain to lower depression risk, Ascherio said. Caffeine is known to elevate mood. It’s also unclear how long a person needs to drink coffee to lower the risk, he said.
About 90 percent of U.S. adults consume caffeine daily, with coffee accounting for about 81 percent of the total daily intake by people older than age 36, the authors said. Americans drank 77.4 billion cups of coffee valued at $35.79 billion in the 12 months ended June 30, according to a Sept. 7 statement by the research firm StudyLogic.
The study included 50,739 women who were part of the Nurses’ Health Study. Researchers looked at questionnaires the women completed from May 1980 to April 2004 to measure caffeine consumption. None of the women had depression at the start of the study in 1996 and they were followed through June 2006.
Researchers found that 2,607 women developed depression from 1996 to 2006. Ninety-five women who drank four or more cups of caffeinated coffee a day were diagnosed with depression during the study period while 670 people in the one cup a week or less were diagnosed.
More than 560 women who drank two to three cups of coffee developed depression over the study. That group was 15 percent less likely to develop the disorder than those who drank one cup or fewer each week, the study found.
“We don’t want to give false hopes to people that drinking coffee will help them not get depressed,” Michelle Riba, a professor of psychiatry at the University of Michigan in Ann Arbor, who wasn’t connected to the study, said in a Sept. 23 telephone interview. “It does give us some information. Clearly more needs to be done on this.”
Ascherio said women who are predisposed to depression may be more likely to avoid caffeine because it affects their sleep or because they are genetically sensitive to caffeine.
The research also showed that regular coffee drinkers were more likely to be smokers and consume more alcohol than those who consumed coffee the least frequently. The regular coffee drinkers were also less likely to be involved in church, community groups or volunteer and had lower rates of obesity, high blood pressure and diabetes, the authors said.
More studies are needed to confirm today’s findings and to explore whether genetic factors that make people predisposed to depression also affect how they metabolize caffeine, he said.
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