In a recent study — The effect of caffeine and stress on auditory hallucinations in a non-clinical sample — Professor Crowe and colleagues measured the effect of stress and caffeine with 92 non-clinical participants.
Five coffees a day or more was found to be enough to increase the participant’s tendency to hallucinate says Professor Crowe.
“High caffeine levels in association with high levels of stressful life events interacted to produce higher levels of ‘hallucination’ in non-clinical participants, indication that further caution needs to be exercised with the use of this overtly ‘safe’ drug,” he says.