It seems that every week there is a new story about coffee in the press. They range from knee-jerk health warnings to studies that show decreased risk of suicide among coffee drinkers. It’s hard to know what to believe.

Existing research has focused mainly on the effects of caffeine on cardiovascular disease (generally finding no overall effect on cardiovascular disease incidence or mortality), inflammation (generally showing modest decreases in markers of systemic inflammation), and particular types of malignant neoplasms, including breast cancer and oesophageal cancer (generally showing no or modest protective effects).

The editors claim this new research is the first large-scale study of coffee consumption to evaluate a mental health outcome in women. The researchers from Harvard School of Public Health conducted a prospective epidemiological study of coffee consumption and depression incidence by taking 50,739 women without depression and following them up for ten years. Coffee consumption was measured by questionnaire and depression was defined as self-reported physician-diagnosed depression and antidepressant use. The researchers used Cox proportional hazards regression models to estimate the relative risk of depression.

Here’s what they found:

• During 10 years of follow-up (1996-2006), 2607 incident cases of depression were identified
• Compared with women who drank one cup of caffeinated coffee or less per week, those who consumed two to three cups per day had a 15% decreased risk of developing depression
• Those who drank four or more cups a day cut their risk by 20%
• Decaffeinated coffee was not associated with depression risk

The authors concluded:

In this large longitudinal study, we found that depression risk decreases with increasing caffeinated coffee consumption. Further investigations are needed to confirm this finding and to determine whether usual caffeinated coffee consumption can contribute to depression prevention.

Lucas, M. et al. Coffee, Caffeine, and Risk of Depression Among Women. Arch Intern Med. 2011;171(17):1571-1578. doi:10.1001/archinternmed.2011.393 [Abstract]