Drink a coffee when you wake up, another after lunch… For many, it’s just a ritual to stay awake. Behind this banal gesture, however, a huge British study suggests a precise link between coffee and mental health. Researchers followed hundreds of thousands of adults for more than a decade to see how their daily cup mixed with their morale.
This work, based on the UK Biobank cohort and published in the journal Journal of Affective Disordersjoin another analysis published in Psychiatry Research. Both converge on the same idea: moderate coffee consumption would be associated with fewer depressive and anxiety symptoms, while very high doses would cause this advantage to be lost. It remains to understand what this “golden mean” actually means.
Two to three cups of coffee: what the UK Biobank study shows
For this new study, Berty Ruping Song’s team examined data from 461,586 adults, aged 40 to 69, without psychiatric disorders at baseline. Everyone indicated on a touch screen how many cups of coffee they drank per day and what type. The researchers then followed their hospital records for an average of 13.4 years, recording more than 18,000 new cases of mood disorders and stress-related disorders.
By analyzing this data, they observed a J-shaped curve: going from zero to two or three cups per day, the risk of being diagnosed with a mental disorder decreased, then increased among the heaviest drinkers. People who consumed 2 to 3 cups of coffee per day had the lowest risk. Beyond five cups, especially of ground coffee, the protective effect disappeared or even reversed.
Coffee, type of drink and differences between men and women
Instant or ground, the profile remained generally the same: the most favorable zone was around two to three cups, with a higher risk among those who exceeded five cups of ground coffee per day compared to non-drinkers. Decaffeinated coffee was not clearly linked to the occurrence of mood disorders or stress-related disorders, which points to a key role for caffeine.
The study also points to a contrast between the sexes. In men, the relationship between coffee and mental health seemed more marked, with a clearer reduction in risk at moderate consumption. In women, the J pattern appeared, but less pronounced. Interestingly, a genetic score of caffeine metabolism did not change these links: fast or slow metabolizers enjoyed the same “optimal point” at 2 to 3 cups.
How coffee acts on the brain and where to place the cursor in daily life
The researchers cite a drop in certain markers of inflammation and an influence via cystatin C to partly explain these results, while recalling that moderate consumption remains a simple benchmark and not a treatment. Cystatin C, a protein used by doctors to measure the efficiency of kidney filtration, also appears to have an impact. Researchers determined that changes in inflammation and kidney function account for a small portion of coffee’s beneficial effect on the brain.
Currently, the results therefore indicate that moderate daily coffee consumption fits well into a healthy lifestyle. Enjoying two to three cups a day could provide slight relief from daily stress.