People with schizophrenia who threaten or attempt suicide have a propensity towards violence, UK researchers believe.
Seena Fazel (University of Oxford) and colleagues studied 1460 adults with schizophrenia who had participated in the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE).
Around three-quarters of the participants were male, the mean age at baseline was 40.6 years, and patients were considered moderately ill. During the 18-month study period 8.3% of participants were rated as violent on at least one occasion, 33.7% reported suicidal ideation, 11.1% threatened to commit suicide and 5.8% attempted suicide.
In univariate analysis, suicidal threats and suicidal attempts were both significantly associated with violence in men and women, with hazard ratios ranging from 2.8 to 9.4. Suicidal ideation was not associated with violence, however.
Multivariate analysis was then performed, taking into account a raft of potential confounders such as age, alcohol and drug misuse, comorbid diagnosis of major depression or antisocial personality disorder, hostility, positive symptomatology and poor impulse control scores.
In most of the multivariate-adjusted analyses, hazard ratios remained statistically significant for both suicidal threats and suicidal attempts. Also, tests of discrimination, calibration, and reclassification assessed the incremental predictive validity of suicidal behaviours for the prediction of violence risk
In a secondary analysis, the researchers showed that people with a history of violence were not at increased risk of future suicidal behaviour, with hazard ratios of 1.3 and 1.0 in men and women, respectively.
Fazel et al hypothesise that the link between suicidal threats/attempts and violence may be mediated by impulsivity, a trait that is thought to comprise both cognitive and behavioural components.
Although impulsivity was adjusted for in the analyses, the measure of impulsivity used in this study – the “poor impulse control” item of the Positive And Negative Symptoms Scale – reflects only the behavioural component, they note.
“Further research should determine whether measures which reflect the cognitive component of impulsivity may account for the association between suicidality and violence,” the team concludes.
The study is published in Schizophrenia Research.
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