Monocyte to Lymphocyte Ratio as the Sole CBC-Derived Inflammatory Index Associated with PANSS-EC Agitation Severity in a Large Psychiatric Cohort

Agitation is a clinically important manifestation across severe mental disorders, yet its routine assessment remains predominantly symptom-based. Complete blood count (CBC)-derived inflammatory indices offer an inexpensive opportunity to complement clinical assessment with an objective biological signal. This study investigated the association of the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), and systemic immune-inflammation index (SII) with agitation severity measured using the Positive and Negative Syndrome Scale-Excited Component (PANSS-EC). An analytical observational cross-sectional study was conducted using 1,571 psychiatric patient records from Mutiara Sukma Hospital in 2025. Secondary data comprised CBC results and PANSS-EC scores; the four inflammatory indices were evaluated using stepwise multiple linear regression. Moderate agitation was the most frequent category (58.24%), followed by severe (22.92%) and mild agitation (18.84%). Mean NLR, PLR, MLR, and SII values showed an upward tendency across increasing agitation severity. In the final regression model, MLR was the only inflammatory index significantly associated with PANSS-EC score (p<0.001), with a positive regression coefficient (beta=3.374), explaining 1.1% of score variance (R2=0.011); NLR, PLR, and SII were not significant in the final model. The selective association of MLR supports a potentially distinct role of monocyte-linked innate immune activity in behavioral excitation. However, the small explained variance indicates that MLR should be interpreted as a complementary rather than stand-alone marker. These findings highlight MLR as a simple, low-cost candidate biomarker for further prospective evaluation in agitation assessment.