Differential temporal links of serum interleukin‑6 with posttraumatic stress disorder and depression after trauma

This study investigated the longitudinal associations between serum interleukin-6 (sIL-6) levels measured shortly after physical injury and the subsequent development of post-traumatic stress disorder (PTSD) and depressive disorder across two years. Adults with moderate to severe physical injuries were prospectively enrolled from a regional trauma center. Within one month of hospitalization, fasting blood samples were collected for sIL-6 measurement, and detailed socio-demographic and clinical data were obtained. PTSD was assessed using the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5), and depressive disorder-including both major and minor depression-was evaluated with the Mini-International Neuropsychiatric Interview (DSM-IV version). Diagnostic evaluations were conducted at 3, 6, 12, and 24 months post-injury. Logistic regression analyses examined time-specific associations between baseline sIL-6 levels and each outcome after adjustment for relevant covariates and Bonferroni correction. Among 923 participants, 112 (12.1%) developed PTSD and 239 (25.9%) developed depressive disorder during follow-up. Higher baseline sIL-6 predicted PTSD at 3 and 6 months and depressive disorder at 3, 6, and 12 months, but not at 24 months. Elevated early post-injury sIL-6 levels are short-term predictors of PTSD and intermediate-term predictors of depression, suggesting time-dependent inflammatory pathways in post-traumatic psychopathology.