Coffee May Cause Hallucinations Brian Handwerk for National Geographic News January 14, 2009 Double-shot lovers take note-the world's most popular psychoactive drug may have a disturbing hidden effect on some of its habitual users. Heavy drinkers of coffee, tea, energy drinks, and other caffeinated beverages are more likely to hallucinate, hear imaginary voices, and even sense the presence of deceased people, a new study suggests. Among the 200 test subjects, those who consumed the equivalent of seven cups of coffee a day were found to be three times more likely to have hallucinatory experiences than those who consumed less than a single cup a day. Lead author Simon Jones, a psychology Ph.D. student at Durham University in the U.K, is intrigued but cautious about the connection. "This hasn't shown that caffeine causes hallucinations, though the data are consistent with that idea," he said. "It could also be that people who have hallucinations are more anxious and worried, so that causes them to consume more caffeine." Ubiquitous Drug Packs Punch Caffeine is much loved for its ability to quickly increase alertness, boost energy, and improve mood. (Read "Caffeine-What's the Buzz?" from National Geographic magazine.) The massively popular drug's effects have been explored intensely. Some studies have revealed possible benefits such as relief from pain and headaches and the easing of asthma symptoms. Others have suggested possible correlations between caffeine use and cancer, fibrocystic breast disease, and osteoporosis. The FDA lists caffeine as a food additive "generally recognized as safe," and most experts agree that moderate consumption of up to 300 milligrams a day (one to two 12-ounce coffees or six to eight 12-ounce cans of soda) is not dangerous. (See National Geographic's caffeine photo gallery) Sensory Disturbances Jones and colleagues speculate in the journal Personality and Individual Differences that the drug may cause hallucinatory experiences by amplifying the physiological effects of stress-including driving increased production of a stress-related hormone known as cortisol. Jones notes that other research has linked some hallucinations to traumatic events like abuse or bereavement, which may make people more sensitive to stress. Jack Bergman, a behavioral pharmacologist at Harvard Medical School unaffiliated with the study, noted that heavy caffeine intake can produce jitteriness and other adverse effects, which typically prompt users to avoid higher doses. "Overdose with much higher intake of caffeine produces myriad effects, one of which may be considered hallucination," he added. "It's important to remember that hallucination can be most simply defined as a sensory disturbance. There certainly are reports that extremely high doses-overdoses-of caffeine can produce sensory disturbances and, in some cases, it may get more complex than just 'seeing stars' or 'hearing noises.' "It's also important to realize that such very high doses of caffeine also produce, in some individuals, paranoid reactions that can intensify the experience of a sensory disturbance." Bergman also noted that psychiatric conditions like psychotic depression can distort the effects of many drugs, including caffeine, so that it is difficult to predict how afflicted individuals will respond to high doses. Study author Jones hopes to continue probing possible links between nutrition and sensory disturbances. "We're planning to look at those who are disturbed by severe hallucinations and see whether dietary changes like caffeine, sugar, or fat intake can help people cope with their hallucinations better," he said.