Reducing violence risk in persons with schizophrenia: olanzapine versus risperidone.

Objective: This study prospectively examined the effectiveness of treatment with olanzapine versus risperidone in reducing violent behavior among patients with schizophrenia under "usual care" conditions in the community.
Method: Participants were 124 adults with DSM-IV-diagnosed schizophrenia-spectrum disorders receiving services in public-sector mental health systems in North Carolina. After enrollment (1997-1999), subjects were followed for 3 years in an observational study with interviews at 6-month intervals to assess treatment, clinical outcomes, and violent behavior. Rates of violence were compared over time between periods of first switch to olanzapine or risperidone and periods following at least 1 year of treatment with each of these medications.
Results: The study found that remaining on olanzapine for 1 year or more significantly lowered violence risk compared to first switch period, but no significant change in violence risk was found for subjects remaining on risperidone for 1 year or more. These results were obtained using multivariable time-series analysis controlling for salient demographic and clinical covariates.
Conclusion: This study found that, in the complex "real world" settings where persons with schizophrenia reside, long-term treatment with olanzapine confers some advantage over risperidone in reducing violence risk. This advantage appears to be at least in part an indirect effect, via improvement in adherence with treatment. Specifically, adherence with prescribed medication was found to mediate the association between olanzapine treatment and reduced violent behavior.