Java is known to give some people the jitters if they drink too much of it. But can it also trigger hallucinations?

It may if you consume enough of it, say British psychologists, who report in the journal Personality and Individual Differences this week that college students they studied said they sometimes heard faux voices after chugging at least seven cups of coffee daily.

But the Durham University researchers acknowledge that their study of 219 coeds doesn’t prove that caffeine, a stimulant in coffee, actually caused them to hallucinate.  For instance, the students who reported hearing voices may have had psychological disorders and been chugging cups of, in this case, instant coffee to help them cope with symptoms, write study co-authors Charles Fernyhough, a developmental psychologist, and grad student Simon Jones.

Some previous research has found that reducing or eliminating caffeinated coffee from the diets of schizophrenics reduces their hallucinations, but other studies haven’t replicated those findings, they note.

The scientists also couldn’t confirm that the students had consumed the amount of coffee they claimed they had.

But if caffeine is involved in triggering imaginary voices, it could be because it causes the body's levels of the stress hormone cortisol to rise, which may influence the development of hallucinations, according to the study.

"This is a first step towards looking at the wider factors associated with hallucinations," Jones said in a statement. "Many such factors are thought to be linked to hallucinations in part because of their impact on the body's reaction to stress. Given the link between food and mood, and particularly between caffeine and the body's response to stress, it seems sensible to examine what a nutritional perspective may add."

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