Among the experiences reported were seeing things that were not there, hearing voices, and sensing the presence of dead people.
However, Mr James stressed more work was needed to pin down the link.
He said: “”Stressed people may simply drink more caffeine.””
And he added: “”Even if caffeine were responsible for hallucinations in some way, the part it plays would be small compared to other factors in life.””
The researchers now plan to investigate whether other aspects of diet, such as sugar and fat consumption, might be associated with hallucinations.
Dr Euan Paul, of the British Coffee Association, stressed the study only focused on people with a very high caffeine intake.
He also said no details were recorded of other substances consumed that might have had hallucinogenic effects.
“”There are literally thousands of well conducted published studies looking at all aspects of the coffee, caffeine and health debate and the overall conclusion clearly demonstrates that moderate caffeine intake, 400-500mg per day, is safe for the general population and may even confer health benefits.””
Recent research has linked high caffeine intake among pregnant women to miscarriage or low birth weight.
Other studies suggested it could help prevent skin cancer, reduce nerve damage associated with multiple sclerosis, or cause problems for diabetes sufferers.
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