Factors associated with violence among Japanese patients with schizophrenia prior to psychiatric emergency hospitalization: a case-controlled study.

BACKGROUND: Numerous studies have examined a wide range of risk factors associated with violence among patients with schizophrenia. However, risk factors linked to different socio-cultural backgrounds remain unclear.

OBJECTIVE: The objectives were to investigate factors associated with violence among Japanese patients with schizophrenia prior to emergency hospitalizations and to compare them with factors found in studies on other populations.

METHODS: We recruited 420 Japanese patients with schizophrenia who had committed violent acts immediately prior to emergency admission to a psychiatric hospital in Tokyo, during the period 1986 to 2005. Cases were compared with controls (non violent hospitalized patients with schizophrenia) matched for gender, age and admission year. All medical records were reviewed retrospectively. Inter-rater reliability tests of assessment were performed. Conditional logistic regression analysis was used to identify factors associated with violence.

RESULTS: The symptoms of gross excitement, prior violence, auditory hallucinations, systematization of delusions, incoherence of speech, delusions of reference, TCO symptoms, living with others and long duration of illness were found to be associated with violence. In contrast, antisocial traits such as substance abuse and antisocial episodes were not recognized as significant violence-associated factors.

CONCLUSION: Violence among Japanese patients with schizophrenia was strongly associated with elements of schizophrenia itself, rather than antisocial traits. This study highlighted associated factors for violence among Japanese patients with schizophrenia which differ distinctly from associated factors in other countries. This result demonstrates that future studies assessing the risk of violence among patients with schizophrenia need to consider cultural and racial differences in cohorts.