Does Caffeine Fuel Hallucinations?

A friend sent me a link to Drink coffee, see dead people which looks at a study which "quizzed 200 students on their caffeine intake and found those with the highest consumption were also more prone to report seeing, or hearing, things that were not there." The article implied that either increased caffeine consumption or the increase in stress hormone (cortisol) caused by caffeine caused the increase in hallucinations. It allowed that one alternate explanation might be that people who had more hallucinations used caffeine to deal with them.

Let me start with medical facts that go against conventional wisdom before picking on the article. There's an incorrect stereotype that someone who sees things or hears things is unusual and has serious problems. Hallucinations are not rare, not certain indicators of mental illness, and rarely as immersive as seen in TV dramas. A lot of sane and normal people very occasionally think they hear someone calling their name when no one's there, or hear a snatch of music when none is playing. A standard symptom of serious fatigue is to see little black dots moving at the edge of one's vision. It's common to interpret a vague shape out of the corner of one's eye as a person.

Even a good article on a scientific study is less useful than looking at the study itself and its data. Plus media is always biased. Even if an article avoids leaning left or right, avoids favoring either the outlandish or the traditional, it is still biased towards being interesting. Writers (and yes, I am feeling self-conscious as I write this) select interesting topics and then try to describe them in an interesting manner. It is entirely possibly (and hopefully likely) that the study only reported the correlation between caffeine and self-reported hallucinations and avoided drawing unsupported conclusions, but that's only mildly interesting to a small group of people. The title of the article "Drink coffee, see dead people" is catchy and the implication is weird and interesting.

There's a difference between perception and interpretation. The fatigue symptom of moving black dots can be interpreted as seeing ants on one's desk. The article says that participants were "sensing the presence of dead people." I'd like to know the specifics. Did they feel a crawling or cold sensation on the backs of their necks? Did they hear a dead person's voice? Did they see a human shape out of the corner of their eye and assume it was a dead person?

The article gives a nod to the logical truth that correlation does not indicate causation by mentioning that hallucinations might increase caffeine consumption instead of the other way around. But it doesn't mention the possibility of a common cause. Lack of sleep and lack of food are known to increase hallucinations. Do you suppose that students with the highest caffeine intake are well-rested and haven't skipped any meals lately? Me neither. I'd like to see a follow up study that controls for sleep habits and diet.

The article mentions "a daily equivalent of seven cups of instant coffee". Flippantly, I'd like to see the data divided by type of coffee; instant versus french press or espresso. I have a completely unsupported belief that coffee connoisseurs understand their sensory input better than those who drink instant. Plus we're smarter.