A new study shows that risk of depression decreases as coffee consumption increases. The findings however apply only to post-menopausal women who smoke.
The research, published in the Archives of Internal Medicine, studied 50,739 women who participated in the Nurses' Health Study, a long-term Harvard study of some of the biggest issues affecting women's health. None of the women, who had an average age of 63, suffered from depression at the start of the study in 1996. By June 2006, researchers followed up and found that, for women who smoked, the more coffee they drank, the less they were at risk of depression.
Compared with women who drank 100 milligrams of coffee or less per day, women who drank four or more cups per day had 20 percent less risk of depression. The association was not seen in non-smoking women, and researchers could not analyze women who drank very high amounts of coffee -- more than six cups per day -- due to an insignificant number of people who consumed such quantities.
Alberto Ascherio, professor of epidemiology and nutrition at Harvard School of Public Health and co-author of the study said, “Regular coffee drinkers have a lower risk of developing depression than non-drinkers.” But he warned, “These are preliminary results that need to be confirmed.”
In the study, the caffeinated coffee was associated with a decline in depression risk among older female smokers, but decaf coffee saw no such association. Oddly, when looking at other caffeinated resources (tea, soda, chocolate), researchers did not see an associated decrease of depression either. Study authors wrote that this could be because an insignificant portion of people made up the group after excluding those who drank one or more cups of coffee per day.
This type of depression is also not the typical kind that may develop in the younger years, researchers noted. Post-menopausal women are at higher risk of depression due to hormone and chemical changes in the brain. Because of this, the association of decreased depression risk cannot be directly linked to younger women.
“The association found in this study should be taken with caution,” said Dr. Sudeepta Varma, assistant professor of psychiatry at NYU Langone Medical Center. “Caffeine, like other stimulants, can be addictive [and] has potential for producing withdrawal symptoms such as low mood. Also, the use of caffeine can cause anxiety, and at times too close to bedtime, insomnia, both of which are symptoms linked to depression.”
More than half of American adults drink some form of coffee each day, according to the National Coffee Association, and caffeine is the most frequently consumed stimulant in the world.
Dr. Ken Robbins, clinical professor of psychiatry at the University of Wisconsin warned, “One has to be careful not to generalize, but it looks like in a large population, there were a significant amount of people who were less likely to be depressed. For someone who hasn't responded to antidepressants or talk therapy, this is something to consider in a trial, assuming there aren't going to be any adverse medical problems.”
While several antidepressants contain stimulants, Harold Koenig, professor of social psychology at Tulane University School of Medicine, said he is “concerned” if people read about the study and decide to use coffee as self-medication. Antidepressants likely have different chemical compositions than coffee, and would likely have a different effect on the brain. ”No doubt, caffeine can temporarily increase mood and energy, but the problem is that the effect does not last, and the dose has to be continually increased to maintain the same effect…Many people experience a caffeine withdrawal when they cut down on their caffeine intake, and this can cause dysphoria and fatigue. Think about how you feel after you drink a high-caffeinated drink and think about how you feel after about two to three hours. Common sense says that the caffeine effect doesn't last, and that people have to pay for whatever improved mood they experience in terms of withdrawal,” he explained.
Previous research, including a study published last year that was conducted among men in Finland, has linked caffeine consumption to a lower risk of depression and suicide. “A couple of past studies found similar results,” said Daniel Evatt, a psychiatry research fellow at the Johns Hopkins School of Medicine, in Baltimore, who was not involved in the new research. “This study validates the association.”
Evatt, who studies the psychological effects of caffeine, is “not terribly convinced” that caffeine can prevent depression. “There's a very strong indication that there is a real relationship there, but that doesn't mean that coffee will stop depression,” he said. “We need to come up with a hypothesis for the mechanism at work, and then try to see what's really happening.” For his part, Evatt stresses that caffeine can have negative consequences for many people, whether they're experiencing depression symptoms or not. “We shouldn't put caffeine in too positive a light,” he said. “Some people have a relationship with caffeine that's similar to an addictive drug. I don't want to pin it as a public health problem, but people can become dependent on coffee and have troubling withdrawal symptoms.”
“There's no need to start drinking coffee,” said Ascherio. “The message is that coffee is safe to drink, with no adverse effects. That's really all that can be said.”
Emma Robertson-Blackmore, assistant professor of psychiatry at the University of Rochester Medical Center, calls the findings “interesting,” but urged caution regarding the link. “Women should aim for a healthy balance in diet, stress reduction and exercise and be mindful of depression symptoms that require help from health professionals,” she advised.
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