Drinking a lot of coffee may do more than just give you the shakes.
People with a high caffeine intake, from coffee, tea, energy drinks, or chocolate, are more likely to experience hallucinations and hear voices, a new study says.
Researchers found that so-called high caffeine users -- those who consume more than the equivalent of seven cups of instant coffee per day -- were three times more likely to hear voices compared to people who drink the equivalent of less than one cup of instant coffee a day.
The researchers asked 200 students about their caffeine intake, their experiences with hallucinations and their stress levels. Some of the participants reported that they see things that are not there, hear voices and sense the presence of dead people.
The research team, from Durham University in the United Kingdom, attributed their findings to the fact that caffeine is known to exacerbate the physiological effects of stress.
The body releases the hormone cortisol when it is under stress, and research has shown that more cortisol is released if a person has recently had caffeine.
The extra boost of cortisol may be the link between excessive caffeine intake and the increased risk of having a hallucinatory experience.
The study is a step toward learning more about the risk factors for hallucinations, the authors said.
"Previous research has highlighted a number of important factors, such as childhood trauma, which may lead to clinically relevant hallucinations," lead study author Simon Jones, a PhD student in Durham University's psychology department, said in a statement.
"Many such factors are thought to be linked to hallucinations in part because of their impact on the body's reaction to stress. Given the link between food and mood, and particularly between caffeine and the body's response to stress, it seems sensible to examine what a nutritional perspective may add."
The findings are published in the journal Personality and Individual Differences.
Caffeine stimulates the central nervous system and when consumed in moderation, has been found to increase capacity for mental or physical labour.
However, its ability to boost alertness is short-lived.
When daily intake exceeds 250 mg, caffeine intoxication, which is characterized by nervousness, irritability, anxiety, muscle twitching, insomnia, headaches and heart palpitations, can set in.
The researchers cautioned that the link between high caffeine intake and hallucinations could be explained by the fact that those who experience hallucinations consume caffeine to cope with the experience.
More work needs to be done on the impact caffeine, and nutrition in general, can have on hallucinations, they said.
