Associations of Anger Expression and Social Anxiety with Cortisol, the Cortisol/DHEA-S Ratio, and Interleukin-6 in Psychiatric Outpatients: An Exploratory Cross-Sectional Study

Background: Chronic psychological stress can alter hypothalamic–pituitary–adrenal (HPA) axis activity and inflammatory signaling. However, the biological correlates of specific stress-related emotional experiences and expression patterns remain incompletely characterized in clinical populations. We therefore examined the associations of anger expression and social anxiety with HPA-axis-related and inflammatory biomarkers in psychiatric outpatients. Methods: In this exploratory, single-center cross-sectional study, clinical records of 85 adults attending their initial visit to the study clinic were retrospectively reviewed. Anger expression was assessed with the Korean State-Trait Anger Expression Inventory (STAXI-K; n = 61) and social anxiety with the Korean version of the Liebowitz Social Anxiety Scale (LSAS; n = 63). Fasting early morning serum concentrations of cortisol, dehydroepiandrosterone sulfate (DHEA-S) and interleukin-6 (IL-6) were measured. Hierarchical linear regression and partial correlation analyses were conducted adjusting for age, sex and body mass index. Additional analyses included left-censored Tobit models and cross-equation Wald tests. Results: Higher social anxiety scores were associated with higher log-transformed IL-6 (n = 63; β = 0.400, p = 0.001), which was the only association that remained significant after false discovery rate (FDR) correction across the nine main predictor–biomarker tests (q = 0.013). This association also remained significant in the reported sensitivity analyses. Higher anger-out scores were associated with lower morning cortisol (n = 61; β = −0.311, p = 0.022) and a lower log-transformed cortisol/DHEA-S ratio (n = 59; β = −0.278, p = 0.037), but neither remained significant after FDR correction (q = 0.084 for both); the ratio association was also sensitive to covariate adjustment. In separate mutually adjusted analyses (n = 56), social anxiety remained associated with log IL-6 (partial r = 0.295, p = 0.034), whereas the anger-in association was not statistically significant (partial r = −0.026, p = 0.858). Cross-equation Wald tests did not detect statistically significant differences between associations with cortisol and log IL-6. Conclusions: In this exploratory study, the association between social anxiety and higher IL-6 remained significant after FDR correction across the nine main tests and after separate adjustment for depressive symptom severity. The inverse associations of anger-out with morning cortisol and the cortisol/DHEA-S ratio did not survive FDR correction. These findings warrant longitudinal replication and do not establish causality or distinct biological pathways.