By Briar Burley
Caffeine is found in things like tea, coffee and energy drinks
Drinking too much tea and coffee makes you more likely to see or hear things that aren't really there, a new study has found.
Research by Durham University shows drinking the equivalent of seven cups of instant coffee a day makes you three times more likely to hallucinate.
Michelle is one of those who could be affected. She told Newsbeat she'd had three cups of tea that morning and would have more that night.
She said: "I'll have at least another five cups when I get home. I love my tea."
But so far she hasn't experienced any hallucinations.
Simon Jones co-wrote the report, which was based on the study of more than 200 students.
He said: "We looked at those who consumed caffeine equivalent to seven cups of coffee a day and compared to those who drank one.
"We found that those in that high group were three times more likely to have heard a person's voice when there was no one there."
People were also more likely to see things that were not actually there, like people or animals or ghosts.
Caffeine, found in things like tea, coffee and energy drinks, stimulates people's central nervous system and can make you feel more alert.
But consuming too much can cause side effects like insomnia.
Rachel is 32 and lives in Leicester. She told Newsbeat: "I get twitchy, just agitated, can't sit still."
Another 30-year-old woman told Newsbeat she drinks several bottles of diet cola a day.
She said: "I can act weird and I talk weird, as if you are high on drugs. That's how you feel sometimes."
Researchers believe the findings show a link between caffeine and the way your body deals with stress.
When stressed the body releases a hormone called Cortisol.
But caffeine makes people release more of this hormone than normal and that could be linked to hallucinations.
The British Coffee Association has criticised the study for focusing on people who drink a lot of caffeine.
They say drinking four to five cups of tea and coffee a day is safe.
Only pregnant women are advised to limit their caffeine consumption.
Tasha works in Café Bocca in Leicester City Centre. She drinks a lot of tea and coffee but says she's never seen something that wasn't there.
"I've never hallucinated," she said. "I've never known anyone hallucinate. No-one's ever complained about hallucinating on coffee. It's a load of rubbish."