What predisposes schizophrenia patients to aggression?

In schizophrenia patients with related psychoses, physical aggression seems to be higher among men, those with lower education, and those diagnosed at an older age, according to a recent Singapore study.

“The study findings demonstrate high internal consistency and a valid factor structure of Buss-Perry Aggression Questionnaire (BPAQ), making it appropriate for assessing aggression in this population,” the researchers said. “Early implementation of risk protocols as well as psycho-education in this vulnerable group may potentially reduce the risk of aggression in patients with psychosis.”

The study included 397 patients (mean age 36.2 years, 50.6 percent men, 74.8 percent Chinese) seeking treatment at the Institute of Mental Health who were administered a cross-sectional survey. Aside from collecting sociodemographic information, the survey also included the following tools: BPAQ, Symptoms Checklist-90 Revised (SCL-90-R), Cut-annoyed-guilty-eye (CAGE), and Drug Abuse Screen Test (DAST-10).

Multiple regression analysis found that compared to men, women had significantly lower scores of physical aggression (β, –1.6; p=0.04) and hostility (β, –1.6; p=0.03). Similarly, participants who had accomplished primary and below (β, 4.6; p=0.03), secondary (β, 2.4; p=0.04), or A-level/polytechnic/vocational/technical (β, 2.1; p=0.05) education also showed significantly higher scores of physical aggression than comparators who had completed an undergraduate degree and above. [Front Psychiatry 2022;12:777388]

In terms of age, participants who had been diagnosed with schizophrenia at ≥31 years showed higher total BPAQ (β, 7.4; p=0.03) and physical aggression (β, 2.7; p=0.03) scores relative to those whose age of onset was deemed to be ≤20 years.

Moreover, anger scores were significantly elevated in those who had been diagnosed at 21–25 years (β, 1.8; p=0.02) and ≥31 years (β, 2.6; p=0.003).

The researchers also reported significant correlations between various scores in the SCL-90-R and BPAQ tools (p<0.001). In particular, the obsessive-compulsive domain of SCL shared a significant and positive correlation with anger scores (β, 1.8; p=0.003), while SCL interpersonal sensitivity correlated with verbal aggression (β, 1.3; p=0.01).

Further, the phobic anxiety and paranoid ideation domains of SCL correlated significantly with total and hostility domain scores of the BPAQ. The hostility domain of SCL had the highest agreement with BPAQ, correlating significantly with total (p<0.001), physical aggression (p<0.001), verbal aggression (p=0.002), and anger (p<0.0001) scores.

“Our research established the factor structure of the BPAQ in an Asian population among outpatients with schizophrenia and related psychoses seeking treatment at a tertiary hospital,” the researchers said. “Our study results highlight the relevance of adapting BPAQ instrument in the hospital setting to enable implementation of targeted interventions and holistic programmes for patients.”

Important study limitations include its single-centre, cross-sectional design, convenience sampling, and the failure to capture data regarding actual instances of aggressive behaviours. Future studies involving larger community-based sampling and reworked data collection tools are needed.