Drinking copious cups of coffee isn’t just bad for your health, it’s also more likely to drive you crazy, or at least crazy enough to hear voices. According to a study published in the academic journal “Personal and Individual Differences,” people who consumed the equivalent of more than seven cups of coffee per day (330 mg) were more likely to have hallucinations than those who consumed less than one cup (10 mg).
The study monitored 200 students from the University of Durham. It asked them about their caffeine intake from coffee, tea, energy drinks, chocolate and caffeine tablets. Of the top 10 per cent, who consumed more than 330 mg of caffeine per day, 41 per cent had experienced a hallucination at some point in their lives. Those who consumed less than 10 mg were much less likely to hallucinate—only 14 per cent had had such an experience.
The exact mechanism linking caffeine and hallucinations hasn’t fully been worked out, says Simon Jones, the lead researcher and a Ph.D. student at Durham University’s psychology department. But it’s likely that the stress hormone cortisol plays a role: caffeine causes the body to release more cortisol, and this hormone stimulates neurotransmitters in the brain, which are linked to hallucinations. “Our study shows an association between caffeine intake and hallucination-proneness in students,” says Charles Fernyhough, co-author of the study and a professor at Durham University’s psychology department.
Many people have had a hallucination at some point in their lives, says Jones. These tend to occur just as one falls asleep or wakes up.
The researchers plan to build on this study, looking at how other food and drink might contribute to hallucinations.