Does Caffeine Reduce the Risk of Depression?
Abstract & Commentary
By Frank W. Ling, MD, Clinical Professor of Obstetrics and Gynecology, Vanderbilt University School of Medicine and Meharry Medical College, Nashville, TN, is Associate Editor for OB/GYN Clinical Alert.
Dr. Ling reports no financial relationships relevant to this field of study.
Synopsis: Among 50,739 U.S. women followed for 10 years, the risk of depression decreased with increasing intake of caffeinated coffee.
Source: Lucas M, et al. Coffee, caffeine, and risk of depression among women. Arch Intern Med 2011;171:1571-1578.
Data were accessed from the nurses’ health study, which enrolled 121,700 U.S. female registered nurses who were 30-55 years old at the outset in 1976. Every 2 years, participants provided information about their lifestyle, medical history, and illnesses via mailed questionnaires. For this study, use of antidepressants in the baseline year of 1996, incomplete history related to depression, symptoms of depression, and previous physician-diagnosed depression were among the exclusion criteria for this study. The final study population of 50,739 women with an average age of 63 years in 1996 provided data through 2006. Food-frequency questionnaires addressed consumption of coffee (caffeinated and decaffeinated), nonherbal tea, caffeinated soft drinks (sugared and low-calorie), and chocolate. Subjects were asked to address usual daily consumption during the previous 12 months, ranging from none to 6 or more. Caffeine content was assumed to be 137 mg/cup of coffee, 47 mg/cup of tea, 46 mg/can of soft drink, and 7 mg/chocolate serving. Incident depression was defined as a new diagnosis of depression by a physician or regular use of antidepressant. Since 1996 was the first year that regular use of an antidepressant was queried, that was used as the baseline.
Between 1996 and 2006, there were 2607 incident cases of clinical depression. The primary finding the authors report is there is an “inverse, age-adjusted, dose-response relationship” between risk of depression and caffeinated coffee (P for trend = 0.03). Consumption of decaffeinated coffee was not associated with a decreased depression risk. Similarly, caffeine sources other than coffee showed no relationship to the risk of developing depression.
Commentary
Because caffeine is considered the most widely consumed psychoactive substance worldwide, with 80% in the form of coffee, the topic is of universal interest. At low-to-moderate levels of consumption, long-term coffee use is known to be associated with improved psychomotor performance, increased energy and vigilance, and a greater sense of well-being. Excessive doses, however, can be associated with reverse effects.
The findings of these Harvard investigators likely will not significantly alter the practice of any of our readers. Many questions certainly remain regarding the validity of these findings. To their credit, the authors are cautious in their interpretation. They note that the incidence of clinical depression was less than that seen in a general population, but discuss how the exclusion criteria eliminated those patients who were most likely to subsequently develop depression.
These data ultimately may prove to be groundbreaking, but for now it remains the first large investigation addressing a mental health outcome related to coffee consumption. Previous research into the health impact of coffee has found no overall deleterious effect on cardiovascular disease, inflammation, or neoplasms. The news about the risk for depression is also apparently reassuring, but certainly does not rise to the level at which a clinician would go so far as to recommend coffee to a patient to prevent depression. The study does highlight how seemingly minor lifestyle issues may well play a significant role in a patient’s overall quality of life. It suggests that the time that we spend just “getting to know our patients” is well worth it.