About 5% of people without mental illness also see or hear something that does not exist from time to time.
The study involved more than 31,000 people from 18 countries from all continents. A prerequisite was the absence of mental illness. The survey and data systematization was carried out by an international team of experts led by scientists from the Brain Institute in Queensland and Harvard Medical School; the results can be found in JAMA Psychiatry (2015).
It turned out that 5% of respondents have ever seen or heard something that was not. Delusional disorder of consciousness was observed in one percent. A third of the total number of participants experienced this or that "imaginary event" only once in their life, and another third - from two to five times.
Interestingly, people in poor countries experience less such experiences than in rich ones; women have it more often than men; indigenous people see or hear something strange more often than emigrants; and, finally, the chance of hallucinations is higher for the unemployed and unmarried.
Scientists emphasize that in all cases we are talking about mentally healthy people and call for a reconsideration of the view on hallucinations. All the secrets of the human brain have not yet been revealed; research results can help find the underlying causes of temporary delusions. And, in addition, since healthy people see or hear the nonexistent, it is necessary to find the line after which a one-time experience develops into a permanent state, signaling mental disorders.