A Cup of Sunshine? Coffee Defends Against Depression

by Carole Jackson, Bottom Line Health

Here’s news that may bring smiles to the faces of coffee lovers. A large new study suggests that drinking caffeinated coffee is associated with a lower rate of depression. Since other studies have already noted links between coffee drinking and potential protection against type 2 diabetes, heart disease, Parkinson’s disease and several types of cancer, one might be tempted to say that there are sufficient “grounds” to say that coffee’s health benefits are plenty potent.

Researchers from the Harvard School of Public Health in Boston examined the health data of nearly 51,000 women (average age 63) who were taking part in the Nurses’ Health Study, an ongoing examination of nurses and their health habits. At the start of the Harvard study, all of the participants were considered “depression free” (no diagnosis of depression from a doctor, no antidepressant use and no severe depressive symptoms per the Mental Health Questionnaire). Every two years, the women were asked to provide information on their caffeine intake as well as whether or not a physician had diagnosed them with depression or prescribed them an antidepressant. The study collected data for 10 years — making this one of the few studies to ever look at the long-term effects of caffeine. Among participants, 82% of the caffeine consumed came from coffee and 13% and 6% came from tea and soft drinks, respectively.

What the researchers discovered: The more caffeinated coffee women drank, the less likely they were to become depressed over the course of the study. For example, women who drank four cups a day were 20% less likely to become depressed than women who drank one or fewer cups a week, and those who drank two to three cups a day had a 15% lower risk. Women who drank decaffeinated coffee were no more or less likely to be depressed than women who drank no coffee at all, which leads the researchers to believe that caffeine itself might explain the link.

It’s important to note that a “cup” was defined as 150 milliliters, which is about five ounces — less than half the size of a 12-ounce “tall” at Starbucks. And the researchers aren’t sure if taking your coffee black, with sugar or with milk will make a difference, since those details weren’t studied. The findings were published in the September 26, 2011 issue of Archives of Internal Medicine.


To try to figure out the answer, I spoke with Michel Lucas, PhD, RD, one of the Harvard epidemiologists who conducted the research. He told me that previous studies have linked caffeine (found in coffee or anything) with the release of dopamine and serotonin, neurotransmitters in the brain that are associated with enhancing mood temporarily. But exactly why caffeine may deflect depression over the long term hasn’t yet been pinned down.

And, the coffee study may come as a surprise to many people who connect caffeine consumption with a spike in anxiety — which often goes hand-in-hand with depression. “A high level of caffeine can increase jitters and nervousness in some people, and could therefore potentially cancel out any mood-enhancing benefit that the caffeinated coffee may bring,” said Dr. Lucas. And since our reactions to caffeine vary greatly by individual, he added, it’s important to know your limits. “Some people drink three cups of caffeinated coffee in one day and find that they can’t sleep and have anxiety, while others can drink six cups a day with no such effect,” he said.

While this finding may be reassuring for people who drink coffee, Dr. Lucas said it doesn’t mean that if you don’t drink coffee, you should start. This study shows only an association between caffeinated coffee and a low risk for depression — more research needs to be done to see if there is a cause-and-effect relationship.

But if you like coffee and it makes you feel good — this is yet another reason to enjoy your morning cup(s) of Joe!


Michel Lucas, PhD, RD, an epidemiologist at the Harvard School of Public Health, Boston.