Drinking several cups of coffee a day may help to prevent depression in women, according to a study.

Four or more cups of caffeinated coffee cut the risk of clinical depression by 20 per cent when compared with drinking one or fewer cups per week.

The US researchers say they cannot be sure of a causal link between coffee consumption and avoiding depression.

However, they adjusted the results to take account of a multitude of other risk factors, such as medical conditions, marital status, smoking and activity levels. They also found no similar association with decaffeinated coffee or other sources of caffeine, including soft drinks, tea and chocolate. The research involved 50,739 women who participated in the Nurses’ Health Study, a major US investigation exploring links between health and lifestyle.

None of the women, who had an average age of 63, had depression at the start of the 10-year study which began in 1996.

The findings have been reported in the journal Archives of Internal Medicine.

Scientists led by Michel Lucas, from the Harvard School of Public Health in Boston, wrote: “Our results support a possible protective effect of caffeine, mainly from coffee consumption, on risk of depression. “Further investigations are needed to confirm this finding and to determine whether usual caffeinated coffee consumption may contribute to prevention or treatment of depression.”

A previous study from Finland found a reduced risk of suicide with progressively higher levels of coffee consumption. This association continued until coffee consumption reached eight to 10 or more cups a day, at which point suicide risk increased.

“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,” said the US researchers.