Immune-impulsivity link: association between peripheral inflammatory ratios and borderline personality disorder

OBJECTIVES: To determine associations between impulsivity and peripheral inflammatory ratios in patients with borderline personality disorder (BPD). METHODS: Consecutive patients aged ≥18 years with a diagnosis of BPD who presented to the Institute of Mental Health and Neurosciences Kashmir, India, between November 2024 and June 2025 were invited to participate. Recent self-harm was recorded. A blood sample (3 mL) was collected from each patient; levels of white blood cells, neutrophils, lymphocytes, monocytes, platelets, and erythrocyte sedimentation rate were recorded. The neutrophil-to-lymphocyte ratio, monocyte-to-lymphocyte ratio (MLR), and platelet-to-lymphocyte ratio were calculated. BPD symptomatology was assessed using the self-report Borderline Personality Questionnaire (BPQ). Impulsivity was assessed using the self-report Urgency, Premeditation, Perseverance, Sensation Seeking-Impulsive Behaviour Scale, short version (UPPS-S). RESULTS: In total, 26 women and seven men (mean age, 21.2 years) were included in the analysis. Of these, 17 reported recent self-harm and the remaining 16 did not; the two groups did not differ significantly in terms of peripheral inflammatory ratios. In Pearson correlation analysis, MLR showed a trend towards correlation with the UPPS-S (r = 0.338, p = 0.055) and BPQ (r = 0.324, p = 0.066). In multivariate regression analysis, MLR remained associated with the UPPS-S (β = 0.460, p = 0.017) and BPQ (β = 0.358, p = 0.056). CONCLUSION: Although patients with BPD with or without recent self-harm did not differ significantly in terms of peripheral inflammatory ratios, the specific association between higher MLR and greater impulsivity suggests that immune abnormalities are linked to impulsivity in BPD.