Academic Stress in Doctoral Research Scholars in Relation to Biochemical Markers and Mental Health Symptoms: A Single-Center Cross-Sectional Study

Background: Doctoral training involves prolonged performance demands, uncertainty, supervisory dependence, and career pressure, yet objective biochemical correlates of academic stress remain incompletely characterized. This study examined academic stress in relation to glycemic, neuroendocrine, inflammatory, and thyroid-related markers, alongside psychological symptoms and sleep quality, in doctoral research scholars. Methods: This cross-sectional study included 203 doctoral research scholars (123 female, 80 male; mean age 27.2 years). Academic stress was assessed using a 34-item doctoral-adapted Academic Stress Scale (AST). Glycated hemoglobin (HbA1c), evening cortisol, C-reactive protein (CRP), and thyroid-stimulating hormone (TSH) were measured as biochemical outcomes. Depression, anxiety, and stress symptoms were assessed using the 21-item Depression Anxiety Stress Scales (DASS-21), and sleep quality using the Pittsburgh Sleep Quality Index (PSQI). Primary associations were examined using linear regression with heteroscedasticity-consistent type 3 (HC3) robust standard errors, adjusted for age, gender, body mass index, and lifestyle activity, with false-discovery-rate (FDR) correction. Results: Mean AST was 109.5 (standard deviation 21.0). Above-normal DASS-21 scores were observed for depression in 64.5%, anxiety in 86.7%, and stress in 49.3%, while 79.3% had poor sleep quality. Higher AST was associated with all four biochemical markers. Per 10-point increase in AST, HbA1c was 0.225 percentage points higher (95% confidence interval 0.158–0.291), evening cortisol 0.502 µg/dL higher (0.299–0.706), CRP 13.9% higher (8.4–19.7%), and TSH 0.125 µIU/mL higher (0.049–0.200); all FDR q ≤ 0.0013. Depression and anxiety severity distributions differed by gender, whereas stress did not. Exploratory analyses showed positive correlations between DASS-21 symptoms and all four biomarkers (Spearman ρ = 0.22–0.58; all FDR q < 0.01). Conclusions: Higher academic stress was associated with variation across glycemic, neuroendocrine, inflammatory, and thyroid-related markers in doctoral scholars, alongside substantial psychological symptom and sleep burden. The cross-sectional design precludes conclusions regarding temporal direction or causality and supports the need for longitudinal research on doctoral health and well-being.