Your daily coffee habit may affect your brain and mood in unexpected ways, study finds
A small study from University College Cork found that caffeinated and decaffeinated coffee were associated with changes in gut microbes, mood and some cognitive test results. The findings suggest coffee may affect people in ways beyond caffeine, but they do not show that gut changes caused the mood or cognitive differences.
The study involved 62 healthy adults, including 31 regular coffee drinkers who paused coffee for two weeks before resuming caffeinated or decaf coffee for three weeks. Both groups reported lower stress, depression and impulsivity; the caffeinated group also reported less anxiety and improved on an attention test, while the decaf group improved on an episodic memory test. Researchers and an outside psychologist cautioned that the small sample, repeated testing and other factors limit conclusions, and that test gains do not establish lasting real-world benefits or treatment for depression.
In short
- Both coffee types were linked to mood and gut changes.
- Caffeinated coffee was associated with less anxiety and better attention scores.
- The small study cannot show coffee caused lasting benefits.
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The case for
The findings offer a reasonable basis to investigate whether coffee, including compounds present in decaf, may influence gut microbes and relate to mood or cognitive performance. The different reported changes across the caffeinated and decaf groups suggest caffeine may not be the only factor worth studying, and the results could help guide larger, longer-term research.
The case against
The study was small and brief, and its reported associations do not show that changes in gut microbes caused changes in mood or test performance. Repeated testing and other factors may explain some gains, which do not establish lasting benefits in daily life or show that coffee can treat depression.
Explained simply
Coffee contains hundreds of compounds, and decaffeinated coffee retains many of them while having most of its caffeine removed. Researchers are interested in whether coffee may be linked to changes in the gut’s microbes, which help break down food and interact with the body.
University College Cork researchers studied healthy adults who regularly drank coffee, asking some to switch to decaf and others to caffeinated coffee after a break. Mood and thinking tests can show short-term differences, but they do not establish that gut changes caused them or that coffee treats mental health conditions.
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