People who drink too much coffee could start seeing ghosts or hearing strange voices, UK research has suggested.
People who drank more than seven cups of instant coffee a day were three times more likely to hallucinate than those who took just one, a study found. A Durham University team questioned 200 students about their caffeine intake, the journal Personality and Individual Differences reported.
However, academics say the findings do not prove a "causal link". They also stress that experiencing hallucinations is not a definite sign of mental illness and that about 3% of people regularly hear voices.
"This is the first step toward looking at the wider factors associated with hallucinations," said psychology PhD student Simon Jones, who led the study.