Prefrontal theta cordance as a potential marker of latent suicidality: a prospective study of psychiatric inpatients

Abstract. Background: Objective biomarkers of suicidality remain limited. Clinical assessment relies largely on self-report and structured interviews, which may be affected by dissimulation. Prefrontal theta cordance (PTC), derived from quantitative electroencephalography (qEEG), has been linked to antidepressant response and may reflect neurobiological processes not captured by clinical assessment. Methods: In this prospective observational study, 43 psychiatric inpatients following suicidal behavior underwent qEEG, Montgomery–Åsberg Depression Rating Scale (MADRS), and Columbia–Suicide Severity Rating Scale (C-SSRS) assessments. Alcohol involvement was evaluated using a Beck-derived item (BSIS), and projective assessment using the Rorschach test (Piotrowski method). Participants were classified into higher and lower suicidality groups based on behavioral C-SSRS indices. Changes in PTC were categorized as increase/persistence or decrease. Results: Increased or persistent PTC was more common in patients with higher suicidality (63%) than in those with lower suicidality (29%) (Fisher's exact test, p = 0.034; OR = 4.16, 95% CI 1.16–15.00). Clinical improvement occurred in both groups and did not differentiate suicidality. Alcohol-related behavior and projective measures were not associated with PTC changes. One patient died by suicide during follow-up despite apparent clinical improvement. Conclusions: PTC was associated with behavioral severity of suicidality and may reflect latent suicide risk not captured by standard clinical assessment.