Background: There is a modest but consistent association between violence and schizophrenia. The consequences of serious violence could be catastrophic for the victims, as well as the patients themselves and the community. Any knowledge that would help to prevent acts of serious violence would be of considerable value for the individual and the society.
Aim: To identify external and clinical risk factors for serious violence in schizophrenia, in addition to considering the strength of the association between the factors assessed and severe violence.
Methods: This was accomplished by a literature survey. One-hundred and two relevant papers were identified that were published during the past 20 years. Forty-four papers were assessed for eligibility. In all, 27 studies including clinical or cognitive variables were reviewed systematically. An effect size was reported where an odds ratio (OR) could be identified or calculated from available data. Five external factors and six clinical domains were evaluated.
Results: Substance abuse is robustly linking schizophrenia and violence. Among the clinical factors, insight, impulsivity, psychopathy, motor speed and a global measure of cognition are the factors with the strongest empirical evidence for an association with severe violence.
Conclusion: This is the first systematic review of risk factors for severe violence in schizophrenia, in which a great number of clinical and external factors have been evaluated. Most of the clinical factors have been compared on effect size. The identified factors that represent an increased risk of violence in patients with schizophrenia should be included in risk assessments.
Keywords: Psychosis; clinical factors; cognition; homicide; risk factors; schizophrenia; violence.