["Scandinavian Journal of Psychology, Volume 67, Issue 2, Page 558-569, April 2026. ", "\nABSTRACT\nTo investigate longitudinal relationships among psychological stress, inflammation biomarkers, and cognitive function over a 9‐year period using data from the Midlife in the United States (MIDUS) study. Structural Equation Modeling (SEM) was conducted on MIDUS Wave 2 data (M2, N = 790), incorporating biomarkers of stress (cortisol, norepinephrine, epinephrine, dopamine), inflammation (interleukin‐6, C‐reactive protein, fibrinogen, soluble ICAM‐1), and cognition (episodic memory, executive function), with follow‐up cognitive outcomes from MIDUS Wave 3 (M3). Confirmatory Factor Analysis (CFA) assessed measurement validity, and key SEM assumptions were tested. CFA indicated acceptable model fit. SEM revealed significant cross‐sectional associations among stress, inflammation, and cognitive variables at baseline. Baseline cognitive function strongly predicted follow‐up cognition 9 years later, indicating high longitudinal stability. However, stress and inflammation biomarkers from M2 did not directly predict M3 cognition. Indirect effects emerged: M2 cognition influenced both M3 executive function and episodic memory through M3 global cognition. Multi‐group analysis showed no gender‐based differences in model paths. Stress and inflammation biomarkers were associated with cognition cross‐sectionally but showed no direct long‐term effects. Findings highlight the relative stability and predictive continuity of midlife cognition rather than substantial mean‐level change, underscoring midlife as a critical window for sustaining cognitive health.\n"]