A cup of coffee to raise the dead

Badscience rips this one apart nicely!

In the news today, a study linking caffeine intake to the risk of hallucinations from psychologist Charles Fernyhough and PhD student Simon Jones at the University of Durham. Apparently high caffeine users – seven cups of instant coffee per day – have three times more hallucinations (including hearing voices) than low caffeine users. The Metro this morning provided a handy ready-reckoner – apparently that equates to just 1.7 cups of takeaway coffee (so watch out all you caffeine fiends out there!)

Now for a reality check. This was an observational study not an interventional one. All they did was ask 200 students about their caffeine intake and hallucinatory experiences. They didn’t actually dose them with caffeine to see what happens. Fernyhough points out:

“Our study shows an association between caffeine intake and hallucination-proneness in students. However, one interpretation may be that those students who were more prone to hallucinations used caffeine to help cope with their experiences. More work is needed to establish whether caffeine consumption, and nutrition in general, has an impact on those kinds of hallucination that cause distress.”

Also, you need to consider the possibility that students with a high caffeine intake may also indulge in other drugs…

Anyway, putting that to one side, they have an interesting hypothesis about how caffeine does its trick. They point out that caffeine increases cortisol, the stress hormone, and that cortisol is linked to some aspects of psychosis. So the increase in cortisol might be expected to trigger hallucinations. And this in turn ties in with other observations of a link between feeling out of control and seeing things that aren’t there.