The 50,739 women with an average age of 63 and who were free of depression at baseline in 1996, were found to have 15% less chance of developing depressive symptoms if they drank two or three cups per day.
Thos who drank four cups of caffeinated coffee per day were 20% less likely to develop depressive symptoms.
Published in the Archives of Internal Medicine, the researchers led by Michel Lucas, PhD, RD, from the Harvard School of Public Health, Boston, Massachusetts, recorded the women’s caffeine habits dating back to 1980, and then analysed depressive states for ten years from 1996 to 2006.
But of the striking results the authors observed they, “cannot prove that caffeine or caffeinated coffee reduces the risk of depression but only suggests the possibility of such a protective effect."
Consumption of decaffeinated coffee was not linked to reduced levels of depression.
The authors noted there had only been other cohort studies with similar aims: one in Finland where among 2232 men 49 cases of depression were identified after a 17.5-year follow-up. But the results were not conclusive.
Two US studies had shown lower suicide rates to be associated with high coffee consumption but only up to a certain point. “It is possible that persons with more severe forms of depression used very high doses of coffee as a form of self-medication that was, nevertheless, insufficient to elevate their mood,” the authors speculated.
For their own study they noted: “We observed an inverse dose-response relationship between caffeine or caffeinated coffee consumption and depression risk, but we were unable to address the effects of very high consumption because only 0.52% of our participants drank 6 or more cups per day of caffeinated coffee.”
Of caffeine’s psychological effects they noted: “Caffeine affects brain function mainly by its antagonist action on the adenosine A2A receptor and, therefore, plays a role in the modulation of dopaminergic transmission.The antagonist effect of caffeine on adenosine also might imply nondopaminergic mechanisms, such as modulation of the release of acetylcholine and serotonin.”
Archives of Internal Medicine
‘Coffee, Caffeine, and Risk of Depression Among Women’
Authors: Michel Lucas, PhD, RD; Fariba Mirzaei, MD, MPH, ScD; An Pan, PhD;
Olivia I. Okereke, MD, SM; Walter C. Willett, MD, DrPH;E´ ilis J. O’Reilly, ScD;
Karestan Koenen, PhD; Alberto Ascherio, MD, DrPH