Adolescents who experience hallucinations just once don't have an increased risk of mental disorders in adulthood, according to Australian research.
But those who had them at age 14 and 21 had a ninefold risk of a psychotic disorder and a significant increase of attempted suicide within their lifetime.
Associate Professor James Scott presented the findings of the Brisbane study to the annual conference of the Royal Australian and New Zealand College of Psychiatrists in Hong Kong.
"About 8 per cent of adolescents will experience some form of audio or visual hallucination," he told AAP.
The research, aimed at finding out if they would develop mental illness later on, used data on 333 people, some who had hallucinations at 14, others who had them at 14 and 21, and a control group of people without hallucinations.
Their mental health was compared at age 30.
Hallucinations at 14 only were found not to be associated with an increased risk of later mental disorders.
But persistent hallucinations, at 14 and 21, were associated with psychotic disorders, eating disorders and substance use disorders at age 30, and they were more likely to have attempted suicide in adulthood.
"This is consistent with other research we have done showing hallucinations are commonly benign and transient.
"But if they do persist, one needs to worry.
"We once equated that if you heard voices, you are going to get schizophrenia - but most don't, it usually goes away as a transient thing."
If they do persist, help should be sought from a health professional for interventions which can reduce the likelihood of the illness progressing to psychosis.
"If you get in very early - reducing stress, having good health management - you reduce the risk of transitioning to psychosis."
Previous studies were limited by measurement of hallucinations at one time-point only and small sample sizes, Prof Scott said.
* The writer travelled to Hong Kong courtesy of the RANZCP.
