A growing body of research suggests that caffeine might offer some protection against depression, but the exact biological mechanisms behind this are still unclear.
A new study by graduate students Elli Cole and Alessandra Grillo, along with UNCG Psychology professor Dr. Suzanne Vrshek-Schallhorn, takes a fresh approach to this question. When we’re stressed, our bodies release a hormone called cortisol. In general, higher levels of cortisol are considered a negative sign, as chronically elevated cortisol may increase the risk of depression and even damage the hippocampus, a part of the brain involved in memory.
For example, people who tend to ruminate—constantly worry or overthink—typically show stronger cortisol reactions to stress. This has been linked to greater vulnerability to stress and depression.
But what about people who drink coffee regularly? Cole and her colleagues wanted to explore whether habitual caffeine consumption might affect cortisol reactivity differently. To test this, they stressed out college students using a classic method: public speaking. Students were asked to explain why they were the best candidate for a student leadership position, while two observers added pressure by looking bored and exchanging annoyed glances.
As expected, the students’ cortisol levels spiked under stress. But the surprising finding was that regular caffeine drinkers showed higher cortisol reactivity—not lower, as one might expect. This mirrors the pattern seen in people who ruminate. However, in the case of caffeine users, the higher cortisol response seemed to offer some protection. In one group of participants, caffeine even appeared to neutralize the usual effects of trait rumination on cortisol levels.
While the findings are still preliminary, they suggest that for some, habitual caffeine use might change the way the body responds to stress, possibly offering a protective effect against depression.
