September 26, 2011 — Risk for depression may decrease as coffee consumption increases, new research suggests.
In a 10-year cohort study of more than 50,000 older women, investigators found that compared with those who drank 1 cup or less of caffeinated coffee per week, those who drank 2 to 3 cups per day had a 15% decreased risk for depression, and those who drank 4 cups or more had a 20% decreased risk.
"This is one of the first major studies to look to this relationship," lead author Michel Lucas, PhD, RD, epidemiologist/nutritionist at Harvard School of Public Health in Boston, Massachusetts, told Medscape Medical News.
"People have often worried that drinking caffeinated coffee might have a bad effect on their health, but there is more and more literature, including this study, showing that caffeine may not have the detrimental effect previously thought," said Dr. Lucas.
The investigators note that because this was an observational study, it did not prove causality and "only suggests the possibility" of a protective effect.
"Further investigations are needed to confirm [the findings] and to determine whether usual caffeinated coffee consumption can contribute to depression prevention," they write.
Still, Dr. Lucas said that it might be okay for clinicians to recommend increasing a patient's coffee intake.
"If depressed patients are refraining themselves to 1 coffee per day because they think that's all they should have, why not try suggesting they drink more, as long as it doesn't go over 4 cups a day? We still need a large randomized controlled trial to look at this effect, but as long as it's not over a certain amount, upping the intake shouldn't hurt, and may be helpful."
The study is published in the September 26 issue of the Archives of Internal Medicine.
World's Most Used Stimulant
"Caffeine is the world's most widely used central nervous system stimulant, with approximately 80% consumed in the form of coffee, " write the researchers.
They note that although few prospective studies have looked at the link between coffee consumption and depression, a few cohort studies have found a "strong inverse association" between coffee consumption and suicide.
However, a study from Finland ( Eur J Epidemiol. 2000;16:789-791) found that although the risk for suicide decreased progressively for those consuming up to 7 cups of coffee per day, the risk started increasing when consumption went over 8 cups a day.
"It was surprising to us that more studies on caffeine and depression haven't been done. People who drink coffee know that it may give more energy, and we know that caffeine has an impact on the brain and on serotonin, which has been associated with depression. We wanted to explore these associations by comparing women who drink more coffee to those who drink less," said Dr. Lucas.
The US Nurses' Health Study began in 1976 with 121,700 women between the ages of 30 and 55 years at enrollment. Updated information on lifestyle and medical history are provided every 2 years through mailed questionnaires.
For this analysis, the investigators examined data on a cohort of 50,739 of the study's participants who did not have any depressive symptoms in 1996 (baseline for this analysis) and were followed-up through June 2006.
In addition to evaluating both caffeinated and decaffeinated coffee consumption, the women supplied information on their use of tea, caffeinated and decaffeinated sodas, and chocolate.
Incident or clinical depression "was defined as self-reported physician-diagnosed depression and antidepressant use," report the researchers.
Significant Inverse Effect
Results showed that 2607 incident cases of depression were found during the 10 years of follow-up.
An overall "inverse, age-adjusted, dose-response relationship was observed between caffeinated coffee and depression risk (P for trend = .03)," write the investigators.
"Further adjustment for alcohol intake did not materially affect the results," they add.
The women who consumed 2 to 3 cups of caffeinated coffee per day had a 0.85 relative risk (RR) for depression (95% confidence interval [CI], 0.75 - 0.95), and those who drank 4 or more cups a day had an RR of 0.80 (95% CI, 0.64 - 0.99; P < .001 for both) compared with those who drank or 1 or fewer cups per week.
In addition, the participants in the highest of the 5 caffeine consumption categories (550 mg/day or more) had an RR of 0.80 (95% CI, 0.68 - 0.95; P = .02) compared with the women in the lowest category (100 mg/day or less).
Because only 0.52% of the women drank 6 or more cups of caffeinated coffee per day, the effects of very high consumption were not able to be addressed in this study.
Decaffeinated coffee, caffeinated tea, sugared soft drinks, and chocolate were not significantly associated with depression risk.
Dr. Lucas noted that these factors were examined in the women who used them and not coffee as their main source of caffeine consumption, and because their numbers were relatively small, it may have affected the results.
Overall, this large prospective cohort study of older women (mean age, 63 years at baseline) showed that "risk of depression decreased in a dose-dependent manner with increasing consumption of caffeinated coffee," write the investigators.
"This study makes an important contribution because it is the first large-scale study to look at this issue in women, and they focused on mental health aspects, as opposed to previous work which has focused on other health conditions," Seth Berkowitz, MD, assistant professor of clinical medicine in the Division of General and Internal Medicine at the University of California, San Francisco, told Medscape Medical News.
Dr. Berkowitz, who is also on the editorial board for the Archives of Internal Medicine, writes in an accompanying editor's note that past research has found no significant effects of caffeine on cardiovascular disease, modest decreases in markers of inflammation, and no or modest protective effects in certain malignant neoplasms.
"Taken together, these results reassure coffee drinkers that there seem to exist no glaringly deleterious health consequences to coffee consumption," he writes.
Dr. Berkowitz told Medscape Medical News that people often say that caffeine gives them more energy or helps them to concentrate more. However, "it is important to quantify in a scientific way" what the effects are on mental activities.
"As clinicians we want to make sure that people aren't doing things that will have them come to harm. And we're looking for things that we may be able to add that can be of benefit. I think in this case, this study adds to the body of evidence that there isn't much harm in coffee consumption. But I don't think we're at the point where we can say, 'drink coffee so you won't get depressed,' because that's not how the study was designed," he said.
"Still, if your patients have questions or are wondering if drinking coffee is bad for them, I think you can provide some assurance that, at least up to the amounts examined here, it doesn't seem to be causing a lot of problems. If they are feeling like it helps them, they should enjoy it in good health."
The study was supported by grants from the National Institutes of Health and from the National Alliance for Research on Schizophrenia and Depression. In addition, Dr. Lucas received a fellowship from the Fonds de recherche en santé du Québec. The study authors and Dr. Berkowitz have disclosed no relevant financial relationships.
Arch Intern Med. 2011;171:1571-1578. Abstract
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Cite this: Coffee May Keep Depression Away - Medscape - Sep 26, 2011.