Research studies around the world involving very large numbers of people have estimated that on average, between five to eight per cent of people who do not have a mental health problem have psychotic-like experiences. In some studies, as many as 40 per cent of adults say they have had them. The number of people having psychotic-like experiences is far greater than the number of people who have a diagnosis of a mental illness involving the symptoms of psychosis.
The research shows that psychotic-like experiences are much more common among adolescents and young people, and that children can also have them. One study in London showed that 66 per cent of almost 8,000 children aged nine to 11 said they had had at least one psychotic-like experience.
Hearing voices and thinking in a paranoid way are the most widespread experiences. Some studies report that between 40 and 70 per cent of young people interviewed said they had heard voices at some time – hearing their name called; the voice of God; or voices of dead relatives, for example.