Investigational transcranial magnetic stimulation measures as predictors of aggression in schizophrenia: A...

Aggressive behaviors associated with schizophrenia are important determinants of the functional outcomes of the illness. Investigational transcranial magnetic stimulation (TMS) measures provide direct assessments of motor cortical inhibition, excitability, and plasticity, and these measures are known to be altered in individuals with schizophrenia. This study aimed to examine the association between these TMS measures and aggressive behavior in individuals with schizophrenia.

79 minimally treated patients with a diagnosis of schizophrenia as per DSM-5 were recruited for the study from Central Institute of Psychiatry, India. Short Interval Cortical Inhibition (SICI), Long Interval Cortical Inhibition (LICI), Cortical Silent Period (CSP), a proxy measure of recruitment gain (SI1mV - RMT), and measures of cortical plasticity were recorded, along with basic clinical data. The Modified Overt Aggression Scale (MOAS) was used to quantify total aggression scores.

CSP (R = 0.322, p = 0.004), SICI (R = -0.33, p = 0.003) and SI1mV - RMT (R = 0.367, p = 0.0008) were significantly correlated with total MOAS scores. A multivariate linear regression model including CSP, SICI, and SI1mV - RMT explained 17 % of the variance in total MOAS scores (p = 0.0036, Cohen's f² = 0.2), indicating moderate predictive utility for clinical risk assessment. A multivariate logistic regression model with the same predictors achieved an AUC of 0.704 (p = 0.005) in distinguishing high aggressors (total MOAS score ≥10) from low aggressors. Despite the overall model being significant, none of the individual predictors reached statistical significance, suggesting possible interaction effects that warrant further exploration. Including other TMS measures and various clinical and sociodemographic variables did not improve the model fit.

TMS measures of cortical inhibition (SICI, CSP) and excitability (SI1mV - RMT) provide neurophysiological biomarkers for predicting aggressive behaviour in schizophrenia. This can potentially enable clinicians to identify high-risk patients for targeted interventions. Cross sectional design and moderate sample size are important limitations of the study.