People who are abused as children may be more prone to developing schizophrenia, research suggests. Psychologists have found evidence of a high rate of childhood physical and sexual abuse among children who were later diagnosed as schizophrenic.
They found a particularly strong link between childhood abuse and hearing voices.
In some cases the voices being heard were those of the people who carried out the abuse.
The researchers also found that the changes in the brain seen in abused children were similar to those found in adults with schizophrenia.
In both, similar parts of the brain, such as the hippocampus, were damaged and brain chemistry was affected the same way.
Stress caused by abuse is thought to alter the development of a child's brain, which at a young age can be moulded by the stimulus it receives.
Lead researcher Dr John Read, from the University of Auckland in New Zealand, said science had to tackle the possible link between upbringing and mental illness head on.
He said: "For far too long efforts to understand and treat people with psychotic experiences have been dominated by simplistic and often unsubstantiated biological and genetic theories.
"It is time to break the silence about how frequently people with psychosis have been abused, whether inside or outside the family."
Dr. John Read
"What we are advocating is a more integrated approach where the horrible life events reported by so many people diagnosed schizophrenic are no longer ignored or inappropriately dismissed as part of their illness.
"It is time to break the silence about how frequently people with psychosis have been abused, whether inside or outside the family.
"I anticipate a degree of outrage, from biological psychiatrists and people acting as spokespersons for relatives' groups, but the facts speak for themselves and cannot be brushed aside because some people find them upsetting."
Paul Corry, of the National Schizophrenia Fellowship, told BBC News Online: "Schizophrenia is a very complex and misunderstood illness.
"Each person experiences the symptoms in a very individual way and it is likely that many factors are involved in one person developing the condition and another person not.
"All the research available points to people with schizophrenia having a genetic predisposition of one kind or another that is then triggered by one or more stressful life events.
"This research appears to make a big and perhaps unsustainable leap from the evidence collected to the conclusions made.
"Much more research into the complex causes, treatments and outcomes for schizophrenia is needed."
Amanda Hall, head of research at the mental health charity SANE, also warned against jumping to conclusions.
She said: ""The finding of a link between childhood abuse and schizophrenia in later life must not be interpreted as evidence of a cause of psychosis.
"This research does not prove that the experience of childhood abuse causes one to go on to develop psychosis in later life.
"It may indicate that those who are genetically predisposed to develop schizophrenia (those who have a family history of mental illness) may be more likely to go on to develop the disorder at a later stage of life compared to those who have no abuse history.
"Thus childhood abuse and family history of schizophrenia may both be seen as additive risk factors for the development of schizophrenia at some stage in the lifespan."
The research is published in the journal Psychiatry: Interpersonal and Biological Processes.