Study finds two to three cups of coffee may cut stress, boost mood

Four cups a day can sound like the point where coffee finally starts pulling its weight, but a massive UK Biobank study suggests the sweet spot for mood and stress sat a little lower: about two to three cups.

Researchers from Fudan University in China tracked 461,586 adults who were in good mental health at the start of the study and followed them for a median 13.4 years. Over that stretch, they recorded 18,220 incident cases of mood disorders and 18,547 incident cases of stress disorders, then mapped those outcomes against daily coffee intake. The result was a J-shaped curve, with the lowest risk landing around two to three cups per day rather than rising in a straight line with every extra mug.

That detail matters for anyone who treats coffee like a daily ritual rather than a supplement. In this analysis, the protective association did not keep improving endlessly at higher intake. The pattern flattened and then changed, which is why four cups may still look good in a headline, but the broader data point to a more modest daily range for the strongest association with better mental health outcomes.

The study also separated instant, ground and decaffeinated coffee, showing that the coffee question was not just about caffeine delivery in a single format. The protective effect against mood disorders was stronger in men than in women, adding another layer of nuance for readers trying to translate the findings into their own routine.

The new paper fits with earlier work that also found the lowest risk for incident depression and anxiety around two to three cups per day. A 2025 study in Scientific Reports added a related note of caution and promise, finding that caffeine intake was associated with later increases in positive affect in naturalistic settings, while links to lower negative affect were less consistent. Taken together, the evidence points to coffee as a modest mood ally, not a magic number stamped on the side of the mug.