You’ve probably heard that excessive caffeine is linked to everything from tremors to irritability, but here’s something that might really make your head spin. A small study by British researchers found that large jolts of caffeine upped the risk of experiencing hallucinations.

Yes, hallucinations.

The researchers studied about two-hundred students at England’s Durham University. Although they didn’t rule out the possibility that some students had psychological issues to begin with, their results showed that students who drank more than seven cups of joe a day were significantly more likely than others to hear imaginary voices.

The researchers aren’t exactly sure how coffee causes hallucinations, but say the most plausible explanation for their findings is that caffeine elevates levels of the stress hormone cortisol.

It’s important to remember that these findings must be taken with a grain of salt. The study can’t say for certain which came first: the caffeine or the psychosis. But previous studies have come to similar conclusions, finding that caffeine increases the number of hallucinations experienced by people with schizophrenia.

The researchers had to take the students’ word that they drank as much caffeine as they claimed. But the average amount of caffeine they consumed on a daily basis… nearly a hundred and fifty milligrams… was similar to that in previously studied college populations.

So the next time you reach for that cuppa joe, don’t be alarmed if you see Juan Valdez and his donkey conversing in the corner. It’s just the caffeine talking.