When they excluded the effects of drugs, they found that one in 20 people (some 5.8%) have had a psychotic experience—such as hallucinations or delusions—in their lifetime. One-third of those said they have had such experiences more than five times. If hallucinations and delusions are not that uncommon, the results hint that psychosis—like other mental oddities—may lie on a spectrum.
Such psychotic episodes may be the result of acute stress, which anyone can suffer. Death in the family, a broken relationship, or even anxiety can trigger mechanisms in the brain resulting in, say, a hallucination.