BIG coffee drinkers are taking a latte break from reality, with half of them likely to hallucinate or hear things.

If the break is supposed to be a stress-buster - as it often is - that makes things worse. And if a cigarette is involved, you're playing with fire.

La Trobe University research has found that stressed coffee lovers are three times more likely to see or hear imaginary things than everyone else.

In tests, they heard Bing Crosby singing White Christmas - or at least thought they did.

Prof Simon Crowe tested 92 people with varied caffeine intake and stress levels. Subjects thought they were doing hearing tests and were initially subjected to Bing.

Then they were played three minutes of static hiss and asked to press a buzzer if they heard snippets of White Christmas in there - which there weren't.

On average, low-caf subjects heard it once. But stressed coffee guzzlers buzzed three times.

"If you are stressed and have a high level of caffeine, you are more likely to notice things that aren't there, see things that aren't there," Prof Crowe said.

For the first test, five cups a day was classed as heavy drinking. But a follow-up produced similar results using caffeine tablets equal to 400ml of brewed coffee.

White Christmas was picked because it had been used in other tests and because, despite what Christmas shoppers feel, it is considered soothing.

Prof Crowe said about 15 per cent of the population reported hallucinatory or delusional experiences, things such as hearing voices or their own thoughts, seeing ghosts, or sensing telepathy.

But Melbourne's coffee set was doubtful a few brews would send people off.

Balwyn barista Elizabeth Watson, 18, doubted her customers were tripping. But Paul Stillen, 23, was open to the idea.

"It's a drug like anything else, and I'm sure if you ate enough chocolate, you'd be seeing things too," he said.

Pixie Beneblis, 26, wondered: "Maybe going on the coffee makes them channel on to another plane?"

And Degraves Espresso barista Daxie Chavez, 22, said some big coffee drinkers got a bit weird.

"Definitely. I find that a lot. Some of the stuff they talk about, it's the most warped conversation -- really left-field conversation," he said.

Prof Crowe said 80 per cent of the world's population had a daily caffeine fix. But, while we are aware of the risks of drugs such as amphetamines, we are cavalier about coffee.

brownt@heraldsun.com.au

Originally published as A cuppa sends us to La La Land