Paul Hammersley, at University of Manchester, and John Read, a New Zealand clinical psychologist, believe that two-thirds of people diagnosed as schizophrenic have suffered physical or sexual abuse and thus it is shown to be a major, if not the major, cause of the illness.
With a proven connection between the symptoms of post-traumatic stress disorder and schizophrenia, they say, many schizophrenic symptoms are actually caused by trauma.
Their evidence includes 40 studies, which revealed childhood or adulthood sexual or physical abuse in the history of the majority of psychiatric patients and a review of 13 studies of schizophrenics found abuse rates from a low of 51% to a high of 97%. Psychiatric patients who report abuse are much more likely to experience hallucinations flashbacks which have become part of the schizophrenic experience and hallucinations or voices that bully them as their abuser did thus causing paranoia and a mistrust of people close to them.
They admit not all schizophrenics suffered trauma and not all abused people develop the illness, but believe less traumatic childhood maltreatment, rather than actual abuse, may be an important difference. In their review of the 33,648 studies conducted into the causes of schizophrenia between 1961 and 2000, they found that less than 1% was spent on examining the impact of parental care. Still, they say, there have been enough studies to suggest negative or confusing early care may be an important addition to abuse as a cause.
Genes may still have a role to play but other evidence Hammersley and Read cite shows that genes alone do not cause the illness. A recent study compared 56 adoptees born to schizophrenic mothers with 96 adoptees whose biological parents did not have the illness. The families were observed extensively when the children were small and all the adoptees were assessed for psychiatric illness in adulthood. It was found that if there was a high genetic risk and it was combined with mystifying care during upbringing, the likelihood of developing schizophrenia was greater - genes alone did not cause the illness.
In addition a recent review revealed that, apart from for Alzheimer's, not a single gene has been shown to play a critical role in any mental illness, while sociological studies show that schizophrenia poor people are several times more likely than the rich to suffer schizophrenia and urban life increases the risk.
Source: University of Manchester, 2006