Their study found that students who consumed more than the equivalent of seven cups of instant coffee a day were three times more likely to have had these kinds of hallucinations compared to people on a single daily cup.
"This is the first step toward looking at the wider factors associated with hallucinations," said Simon Jones, a psychologist at Durham University in Britain who led the study.
The findings are also the latest in mounting evidence indicating the amount of caffeine a person consumes may directly affect a person's health.
Recent studies have suggested caffeine may lower a woman's risk of ovarian cancer while others have found too much doubles the risk of miscarriage.
Currently, people treated for hallucinations receive drugs or counselling but Jones said his research aims to explore whether changing a person's diet could help.
"This is the first time to my knowledge caffeine and hallucinations have been looked at," Jones said in a telephone interview.
For the study published in the journal Personality and Individual Differences, Jones and colleagues asked 200 students about their typical intake of coffee, tea, energy drinks and other products containing caffeine. They also measured stress.
Students who consumed the most caffeine were more likely to report hallucinatory experiences such as hearing voices and seeing things that are not there, the researchers said.
The stress hormone cortisol may help explain the link, Jones said. Researchers know the body releases more of the hormone after people consume caffeine, and this extra boost may fuel hallucinations.
They did not ask the students how much they slept.
The next step is to test whether caffeine is actually causing hallucinations or whether people who have them simply consume more caffeine when under pressure, Jones said.
"It may be that those who have hallucinations have high levels of worry and anxiety and that leads them to consume more caffeine," Jones said.
Last Mod: 14 Ocak 2009, 15:58