Some people with schizophrenia who become violent may do so for reasons unrelated to their current illness, according to a new study analyzing data from the Clinical Antipsychotic Trials for Intervention Effectiveness (CATIE). CATIE was funded by the National Institutes of Health's National Institute of Mental Health (NIMH). The study was published online on June 30, 2007, in the journal Law and Human Behavior.
"Most people with schizophrenia are not violent," said NIMH Director Thomas R. Insel, M.D. "But this study indicates that the likelihood of violence is higher among people with schizophrenia who also have a history of other disorders, namely childhood conduct problems."
Using data from 1,445 CATIE participants, Jeffrey Swanson, Ph.D., of Duke University, and colleagues examined the relationship between childhood antisocial behavior, including conduct disorder symptoms, and adult violence among people with schizophrenia. The overall percentage of participants who committed acts of violence was 19 percent. Those with a history of childhood conduct problems reported violence twice as frequently (28 percent) as those without conduct problems (14 percent). In both groups, violence was more likely among those who were unemployed or underemployed, living with family or in restrictive settings (such as a halfway house or hospital), been recently arrested, or involved with the police.
Violence was associated with alcohol and substance abuse in both groups. But unlike the group without childhood conduct problems, violence in the group with childhood conduct problems was associated even with levels of alcohol and substance use considered below the threshold for abuse.
The researchers also found that psychotic symptoms were not significantly associated with violence among those participants with a history of childhood conduct problems. In contrast, the presence of psychotic symptoms was associated with an increase in violence among participants without a history of childhood conduct problems.
Swanson and colleagues theorize that there may be two pathways in which adults with schizophrenia may become violent--one in which pre-existing conditions like that of antisocial conduct in childhood, regardless of the presence of psychotic symptoms, may link to violence, and one in which psychotic symptoms of schizophrenia themselves may link to violence.
Based on their theory, the researchers suggest that the antipsychotic medications used to treat psychosis may not be sufficient to treat violent symptoms in people who are at a higher risk due to pre-existing antisocial conduct conditions.
The researchers note that other studies have already found a strong link between childhood conduct problems and adult violence, with or without the presence of schizophrenia. This study adds evidence to the notion that a more targeted treatment should be employed for schizophrenia patients with conduct disorder histories.
"Doctors should take into account their patients' histories before deciding on a treatment approach," said Dr. Swanson. "They should consider specific interventions aimed at preventing further violence, especially among their schizophrenia patients who have a history of childhood conduct problems.
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