A recent study hit the headlines reporting a link between caffeine intake and susceptibility to hallucinations. I’ve just read the paper and it’s an interesting well-conducted correlational study, but what struck me was the wackiness of the headlines it generated.
The study, led by researcher Simon Jones, was inspired by previous scientific work that has found a link between the stress-related hormone cortisol and psychosis.
Caffeine is known to interact with stress to increase cortisol levels further, so the researchers wondered whether there would be a direct link between caffeine intake and psychosis-type changes in thoughts and perception in people without a mental illness.
They asked 219 students to fill in well-validated standardised questionnaires relating to caffeine intake, stress, persecutory thoughts and hallucinatory experience and found that caffeine intake was associated with a small but reliable increase in susceptibility to hallucinations.
Actually, stress accounted for more hallucination susceptibility than caffeine, but as the first study to show an association between perceptual distortion and the world’s most popular stimulant in healthy people, it’s useful research.
I will now recount some of the headlines:
Coffee addicts see dead people
Caffeine, Responsible For Hallucinations
Did You See That Pink Elephant?
Too Much Coffee Can Cause You To Freak Out, Man
Coffee may make you see ghosts
Coffee linked to ‘visions’
‘Coffeeholics wake the dead’
If you think I’m cherry picking, these are actually fairly typical.
The news stories are a strange mix between an obsession with ghosts, which came from God knows where, and a profound confusion between correlation and causation.
UPDATE: I notice Bad Science has just picked up on the same study, and the same media obsession with ghosts, but also looks at a common element of the stories claiming that 7 cups of coffee a day ‘triples’ the risk of hallucinations – which didn’t appear in the paper but was apparently sourced from a bit of ad-hoc jiggery pokery for the press-release.
Link to DOI entry and study summary.
Link to sensible write-up from Science Daily.
Mind Hacks 
This world is teetering like a “Drunken Hut”. I see things, but then I have BAMD (swiss-cheese conrneas). I took PM Tylenol once and fell on my face for four hours, face-dwon, on a hard floor. Only once. My daughter can’t feel her limbs if she takes Aleve (neither can Alzheimer’s sufferers). A friend of ours ruined his Esophegus (?spelling) on Ibuprofin. I once counted ill-effects and contraindications of some meds advertised on TV. There were 21 of them as opposed to only one beneficial effect.
We were better off simply chewing the bark of the Weeping Willow tree. Those Sioux knew what they were doing.
I have experienced hallucinations for the majority of my life and it’s no surprise that my idiot mother used pump me full of coffee when I was a tiny tot. Whenever I stop drinking coffee and caffeine laced drinks, I grind to a complete halt, ie. no thoughts at all and simply stand in one spot all day, so perhaps my neural networking relies on caffeine to function. So, I can say without any doubt that caffeine does cause hallucinations, just like most poison does, from vegetation.