Sydney, June 6 (IANS) Coffee may benefit health in some ways, but beware. Drinking too many cups could bring on hallucinations.

Five coffees a day or more was found to be enough to increase the participant's tendency to hallucinate, says Simon Crowe, professor of psychology at the La Trobe University.

Hallucinations are false perceptions that an individual has that do not exist. For example, a person may hear, see or smell things that are not there.

Crowe and colleagues at the University's School of Psychological Sciences measured the effect of stress and caffeine with 92 non-clinical participants, according to a La Trobe statement.

Participants were assigned to either a high or a low stress condition and a high or a low caffeine condition on the basis of self-report. They were then asked to listen to white noise and to report each time they heard Bing Crosby's rendition of "White Christmas" during the white noise.

White noise is a type that is produced by combining sounds of all different frequencies together, just as white light is produced by a combination of seven colours.

The song was never played. The results indicated that the interaction of stress and caffeine had a significant effect on the reported frequency of hearing "White Christmas."

The participants with high levels of stress or who consumed high levels of caffeine were more likely to hear the song.

"The combination of caffeine and stress affect the likelihood of an individual experiencing a psychosis-like symptom," says Crowe.