Inflammatory Indices are Associated with Non-Suicidal Self-Injury in Adolescents with Major Depressive Disorder

Background . The neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-lymphocyte ratio (PLR), and C-reactive protein (CRP)-albumin ratio (CAR) constitute peripheral inflammatory indices. This study aimed to evaluate the correlation between these inflammatory indices and non-suicidal self-injury (NSSI) behavior in adolescents with major depressive disorder (MDD). Methods. Adolescents diagnosed with MDD were enrolled in this study. All participants underwent psychological and biochemical assessments and were classified into two groups based on the presence or absence of NSSI. NLR, MLR, PLR, and CAR were calculated from complete blood counts. Results. A total of 101 adolescents with MDD were included. No significant differences were observed in the demographic data between the groups. The NSSI group had significantly higher levels of white blood cells, neutrophils, high-sensitivity-CRP, NLR, MLR, and CAR, and lower albumin levels than the non-NSSI group. Multivariate regression analysis revealed that NLR and MLR were independently associated with NSSI. The proposed cut-off values were NLR = 1.23 (sensitivity = 70.2% and specificity = 59.1%) and MLR = 0.14 (sensitivity = 77.2% and specificity = 43.2%). Conclusions. Systemic inflammation may play a role in NSSI among adolescents with MDD. NLR and MLR, as cost-effective and easily accessible indices, are associated with NSSI, but further longitudinal studies are required to determine their predictive value.