Women who drink coffee may have a lower risk of depression, according to a study from the Harvard School of Public Health.
Several recent studies have looked at a possible link between coffee and suicide, and found that coffee drinkers were less likely to kill themselves.
Depression can contribute to suicide, so a logical question might be, does coffee lower the risk of depression?
In this new study, published in the Archives of Internal Medicine, researchers used data from an ongoing project called the "Nurses' Health Study." Women in the study periodically answer questionnaires about their health and lifestyle.
Some 50,000 nurses who reported their coffee consumption and depression status were included in this study.
Researchers found that women who drank more coffee were less likely to be diagnosed with depression. However, the association is not necessarily a cause-and-effect relationship.
"This study can not prove that caffeine reduces the risk of depression," says Michel Lucas, of the Harvard School of Public Health, "but only suggests the possibility of such protective effect."
The lower risk of depression was not observed in people who drink decaffeinated coffee. Also, nurses in the study who reported drinking tea and other beverages with caffeine didn't show a significant change in their risk of depression, possibly because of the much lower levels of caffeine in those drinks.
Lucas say the study cannot answer whether coffee possibly helps protect against depression, but he says caffeine does have biochemical effects that might explain why coffee-drinkers ? or, more accurately, caffeine-users ? are less likely to be depressed.
"We cannot assume causality in this study. It suggests some possibilities. As we know, caffeine is a well-known psycho-stimulant, which increases also a sensation of well-being and energy."
Lucas says caffeine is also associated with regulation of dopamine and serotonin, chemical neurotransmitters linked to mood and depression.
Future research may prove whether there is a cause-and-effect relationship between coffee-drinking and a lower risk of depression. But for now, the Lucas says, "If you're worrying about your drinking cups of coffee, then I think this study is a little bit reassuring for people that like coffee."
Michel Lucas of the Harvard School of Public Health and his colleagues published their study on the link between coffee consumption and depression in the journal, Archives of Internal Medicine.