Some schizophrenia patients become less prone to violence when taking medication, but those with a history of childhood conduct problems continue to pose a higher risk even with treatment, according to a new study by researchers at Duke University Medical Center.
"This is the first large randomized controlled study to compare the effectiveness of several commonly-prescribed medications for schizophrenia on reducing community violence," said Jeffrey Swanson, professor in psychiatry and behavioural sciences and the study’s lead author. "Serious violent behaviour is not frequent among people with schizophrenia, but when it does occur, the results can be costly and tragic."
The study found that violence declined significantly when patients took antipsychotic medications as prescribed, but only among patients whose prior risk for violence could be linked to psychotic symptoms.
The researchers identified a subgroup of schizophrenia patients with a history of childhood conduct problems who were more likely to be violent at the beginning of the study. Among these patients, violence was not strongly related to psychotic symptoms, and did not significantly decline with adherence to prescribed antipsychotic medication during the six-month study period.
The new results, which are from the National Institute of Mental Health’s Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) study, are published in the July issue of The British Journal of Psychiatry.
"In the past, we’ve not understood very well why a small proportion of patients with schizophrenia become seriously violent, while most do not–and why medication seems to prevent violent behaviour in some and not others," said Marvin Swartz, professor of psychiatry and co-author of the study. "These findings tell us that people with schizophrenia may behave violently for reasons not directly related to their mental illness. If that’s the case, then treatment for psychotic symptoms alone may not eliminate the risk of violence."
Researchers found that a number of factors contributed to violent acts independently of the person’s schizophrenia. In addition to childhood conduct problems, substance abuse, being the victim of past violent acts, poverty and living with others, rather than alone, were all predictors of violent behaviour.
Medication is the primary course of schizophrenia treatment to reduce symptoms and hopefully prevent violent acts. This study found that newer antipsychotics are as effective as older medications in reducing violence among people with schizophrenia.
"Contrary to the expectations of many clinicians and some research, this study found no benefit for newer medications over an older medication in reducing the risk for violence over the six-month study period," Swanson said. "In fact, one of the newer medications, quetiapine, performed worse than the first-generation drug perphenanize."
The CATIE study included 1,445 patients with schizophrenia who were randomly assigned to treatment with one of five antipsychotic medications, including olanzapine, perphenanize, quetiapine, risperidone, or ziprasidone.
"Antipsychotic drugs may help reduce violence risk, but they don’t address all of the causes of violent behavior and they don’t help at all if people can’t or won’t take the medication prescribed. We also need interventions to help patients stay engaged in treatment," Swartz added.
(Source: The British Journal of Psychiatry: Duke University Medical Center: July 2008)