Among people with schizophrenia, those whose parents have a history of violence may be more likely to commit violent acts themselves, a new study suggests.

The findings, reported in the Journal of Clinical Psychiatry, suggest that assessing family history of violence could help doctors predict which schizophrenia patients are at greatest risk of violent behavior.

Schizophrenia is a brain disorder that causes people to break from reality, with symptoms such as hallucinations, paranoia and unusual thoughts and perceptions.

Most people with schizophrenia are not violent, but studies show that they are more likely than people without the disorder to commit violent crimes. This is especially true if a person with schizophrenia abuses drugs or alcohol, or had a history of violence before developing the brain disorder.

These latest findings suggest that the risk is also elevated when a patient’s parents have a violent history, according to the researchers, led by Dr. Seena Fazel of Warneford Hospital in Oxford, UK.

Using data from Sweden’s system of national registers, Fazel’s team found that among more than 13,800 schizophrenia patients, those with a parent who’d been convicted of a violent crime were 65 percent to 83 percent more likely to commit a violent act as well.

This held true regardless of factors like family income, patients’ education levels and alcohol or drug abuse.

The reasons for the link are not entirely clear, but it could indicate a genetic propensity toward violent behavior or the influence of growing up with a violence-prone parent, according to Fazel and her colleagues.

Whatever the reasons, the researchers conclude, the findings suggest that doctors should consider family history of violence when trying to judge schizophrenia patients’ risk of violent behavior.

SOURCE: Journal of Clinical Psychiatry, March 2009.