Many children go through the phase of talking to imaginary friends and their favourite stuffed animals. But researchers warn that some as young as 12 are also having hallucinations and delusions, which could be early signs of psychosis.
In a study of British 12-year-olds, the kids were asked whether they had ever seen things or heard voices that weren't really there, and then asked careful follow-up questions.
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The children who exhibited these symptoms had many of the same risk factors that are known to correlate with adult schizophrenia, including genetic, social, neurodevelopmental, home-rearing and behavioural risks.
"We don't want to be unduly alarmist, but this is also not something to dismiss," said co-author Terrie Moffitt, the Knut Schmidt Nielsen professor of psychology and neuroscience and psychiatry n behavioural sciences at Duke University.
The children were participants in the long-term Environmental Risk Longitudinal Twin Study in Britain, which includes 2,232 children who have been tracked since age 5 and reassessed at 7, 10 and 12.
The findings provide more clues to the development of schizophrenia, but don't solve any questions by themselves, said co-author Richard Keefe.
Psychotic symptoms in childhood also can be a marker of impaired developmental processes, and are something caregivers should look for, said Moffitt.
While the incidence of psychotic symptoms in this study was around 5 or 6 percent, the adult incidence of schizophrenia is believed to be about 1 percent, added Keefe.
However, there are some recent findings that many more people experience hallucinations and delusions without being diagnosed as psychotic, he said.
The study appears in a recent issue of Archives of General Psychiatry.