Sexually abused children are likely to develop psychotic illnesses later in life, a study says.

Researchers from Monash University, Australia, say that such children are more likely to develop schizophrenia and other psychotic disorders, which includes post-traumatic stress disorder, suicidal behaviour and substance abuse.

Margaret Cutajar and her colleagues from Monash compared rates of psychiatric disorders among 2,759 sexually abused children under 16 years with 4,938 individuals from a comparison group, reports the journal Archives of General Psychiatry.

Over a 30-year period, individuals who had experienced childhood sexual abuse had double the rate of psychosis and schizophrenia disorders than those in the comparison group, the study found.

Many cases of childhood sexual abuse never come to light, and the overall population of abused children may be significantly higher than the official figures, a Monash University statement said.

"Children who come to attention following sexual abuse should receive ongoing clinical and social support in the knowledge that they are at greater risk of developing a psychotic illness," the authors said.