CAFFEINATED energy drinks may trigger a psychotic episode in people with mental illness, an expert has warned after documenting the case of a young man with schizophrenia.

the 27-year-old Maori man had two separate psychotic events a week apart linked to his intake of the drink Demon Shot.

Professor David Menkes said these events occurred at a time when the man, who was prone to persecutory thought and hallucinations, was otherwise responding well to anti-psychotic medication.

in the first instance, the man drank two 60ml bottles of Demon Shot and later reported experiencing recurrent thoughts, over several hours, of "people wanting to harm him".

"one week later, he drank three Demon Shots over 15 minutes," said Prof Menkes, who is Associate Professor of Psychiatry at Auckland University.

"he was observed to be emotionally labile (moving from one point to another) – initially laughing and talkative, later becoming restless, withdrawn and argumentative."

other symptoms included a rapid pulse and insomnia, which took 24 hours to subside.

the man described again having had paranoid thoughts over several hours and an experience "consistent with a psychotic episode".

"the fact that our patient had the same reaction on two distinct occasions is important," Prof Menkes said.

he said there was known cases where a high intake of caffeine may exacerbate a psychotic condition though this appeared to be the first linked to consuming energy drinks.

the man's case was "evidence that some patients with treated schizophrenia may be vulnerable to exacerbation of their illness by caffeine-containing energy drinks", he said.

Demon Shot drinks are widely available in Australia and new Zealand and they contain 200mg caffeine plus taurine, B vitamins and guarana, which may have other stimulant properties.

according to its website, each Demon Shot provides a "massive energy hit that delivers up to six hours of concentrated mental and physical responsiveness".

the drinks also carry a warning, which says it should not be consumed by people sensitive to caffeine, and no more than two drinks a day.

the case is detailed in a letter published in the latest edition of the Medical Journal of Australia.