Healthy young men and women who had more than seven cups of instant coffee a day were three times more likely to hear or see things that were not there. It is thought that caffeine boosts levels of cortisol, a stress hormone.

The Durham University researchers asked 219 students to document their caffeine intake, working on the principle that a cup of instant coffee contains 45mg of caffeine. Coffee brewed at home contains more than twice as much, while that from cafes such as Starbucks can have almost 190mg of caffeine.

The volunteers were also asked how often they suffered hallucinations. The high caffeine users were three times as likely to have had problems as those who rarely drank coffee. Large amounts of caffeine also made people more likely to think they could sense the presence of ghosts, the journal Personality and Individual Differences reports.

So did I have that extra shot or just think I did?

And sometimes there just isn't enough coffee in the world...

The original was here