Inflammatory markers elevated in adolescent MDD with both self-injury and suicide attempts

This retrospective cross-sectional study analyzed 618 adolescent inpatients with major depressive disorder (MDD) categorized into four groups: pure MDD without self-harm (n=382), non-suicidal self-injury (NSSI)-only (n=131), suicide attempt (SA)-only (n=41), and a comorbid NSSI+SA group (n=64). The study examined complete blood count parameters and derived inflammatory markers—neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII)—to differentiate these clinical subtypes.

The NSSI+SA comorbid group exhibited a distinct inflammatory signature compared to the other subgroups. They had significantly elevated neutrophils, NLR, MLR, PLR, and SII, alongside reduced lymphocytes (all p < 0.05). NLR and SII were identified as independent predictors for distinguishing the comorbid group from the pure MDD group. A receiver operating characteristic (ROC) curve analysis demonstrated that NLR and SII had moderate discriminatory power for identifying the NSSI+SA comorbid group, though specific area-under-the-curve values were not reported.

Safety and tolerability data were not reported. Key limitations include the observational, cross-sectional design, which precludes causal inference. The study did not report absolute numbers, effect sizes, or confidence intervals for the main results, limiting precision. The findings represent an association between inflammatory markers and a specific, high-risk clinical phenotype of adolescent MDD. Their relevance to clinical practice is currently restrained to hypothesis generation, as prospective studies are needed to determine if these markers have predictive or monitoring utility.