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BACKGROUND:

The aim of the study was to analyse the triggering or acute risk effect of psychiatric symptoms and interpersonal stressors on criminal violence.

METHOD:

One hundred and thirty three violent offenders were recruited from a forensic psychiatric evaluation (FPE) unit and a national prison evaluation unit in Sweden during 2002-2003, and were interviewed about trigger exposures. A case-crossover design was used eliminating long-term within individual confounding.

RESULTS:

Suicidal ideation or parasuicide within 24 h before the violent event conferred a ninefold risk increase. In contrast, violent ideation did not trigger criminal violence. Hallucinations yielded a fourfold risk increase, whereas paranoid thoughts were associated with a small and statistically non-significant risk increase. Acute conflicts with others and being denied psychiatric care within 24 h before violence also increased the risk of acting violently.

CONCLUSIONS:

Some tested psychiatric symptoms and stressors triggered criminal violence, whereas others did not. The case-crossover design may be particularly useful for the study of triggers of violence.