Harvard Mental Health Letter

Why coffee perks people up

A study suggests that coffee not only wakes people up, but also may offer some protection against depression. What's less clear is why this might be. Researchers at the Harvard School of Public Health and Brigham and Women's Hospital analyzed data collected from nearly 51,000 women participating in the Nurses' Health Study, all free of depression in 1996. The researchers then determined how many of the women had developed depression a decade later and compared their caffeine intake to determine whether it affected risk. (They also controlled for other health and lifestyle factors such as weight, cigarette smoking, and exercise.) By 2006, 2,607 women were diagnosed with depression or had started taking antidepressants. The researchers found an inverse dose-response relationship between caffeine intake and mood: the more caffeine a woman ingested per day, the lower the likelihood that she developed depression during the study period. Women who drank the most caffeinated coffee per day were 20% less likely to develop depression than women who drank the least. 
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