According to research, women who drink at least two cups of coffee a day have a smaller chance of getting depression. Authors, while not clear about the reasons for this correlation, theorize that caffeine in coffee may have an impact on the chemical makeup of the brain. Decaffeinated coffee did not have the same results.
The research was published in Archives of Internal Medicine, and came as a result of studying over 50,000 female nurses in the US. They have recommended more work be done to understand the correlation, it being too soon to advise that women drink more coffee.
The Harvard Medical School team published the results after following the health of the women throughout ten years between 1996 and 2006. The results were given in the form of questionnaires. Of the 50,000 women, only 2,600 developed symptoms of depression at any point during this period. These tended to be women who either did not drink coffee or drank very little coffee. Compared with those who drank one cup of coffee, those who drank two or three each day had a 15% less chance of depression. Risk was cut by 20% if women drank four or more cups a day.
Other factors included that women who drank coffee regularly were more likely to smoke and drink and less likely to be involved in church, volunteer, or community groups. In addition, they were less likely to be overweight or have diseases like high blood pressure or diabetes.
Once these variables had been controlled for, the same correlation remained. Other researchers had previously discovered that drinking coffee correlated with lower suicide rates. Caffiene is known to enhance wellbeing and energy, and the researchers suspect that this is the reason behind the results. It has a physical effect on brain function by blocking chemical receptors, though more research will need to be done before finding a cause and effect relationship.
An alternate reason for the findings could be that those with low moods chose not to drink coffee as it did contain caffeine, as it would not help with sleep problems prevalent in depression and can increase anxiety. If the results are accurate, coffee sales could increase, a good sign for the industry.