From Science:
If your cup of joe starts talking to you, chances are you're a caffeine addict. People who drink a lot of coffee or other caffeinated beverages are more likely to report hearing voices or having out-of-body experiences than those who go easy on the strong stuff, according to a new study. The link between caffeine and hallucinations makes sense physiologically. When stressed, the body amps up its production of the hormone cortisol, which can cause people to see and hear things that aren't there. Cortisol is also regulated by caffeine, which increases hard-core coffee and tea drinkers' responses to stress. Intrigued by the connection, psychologists Simon Jones and Charles Fernyhough of Durham University in the U.K. designed an online survey that was e-mailed to university students. The 200-plus participants, most of them women, answered questions such as “How often do you drink … brewed coffee?” and ranked the relevance of statements such as “I have had a sensation … that I left my body temporarily.”
On average, the students drank the caffeine equivalent of about three cups of strong tea or instant coffee per day, Jones and Fernyhough report today in the journal Personality and Individual Differences. More importantly, the data show that individuals who consumed more caffeine were more likely to hallucinate.
More here.
