Does the cortisol: CRP ratio inform the measurement of individual burden of illness for depression in community samples?

Longitudinal associations between salivary cortisol to C-reactive protein ratios and psychological well-being in Chinese adults

BACKGROUND

Salivary C-reactive protein (CRP) could be a viable biomarker of inflammation and has been associated with stress outcomes. The hypothalamic-pituitary-adrenal axis can modulate stress-related inflammation. This study aimed to evaluate the interaction effects of immune-endocrine markers on psychological outcomes.

METHODS

The study participants were 52 healthy Chinese adults who collected 10 saliva samples over 2 consecutive days at baseline. The participants completed validated measures on anxiety, depression, positive affect, and sleep disturbance at baseline and 1 month later. The stability and diurnal patterns of salivary cortisol and CRP were investigated via paired t-tests and repeated-measures analyses of variance. Regression analysis was used to examine the longitudinal associations between immune-endocrine markers and their interactions (cortisol [Cort]: morning CRP [CRP_morn] and Cort:CRP_even) and psychological measures.

RESULTS

Salivary cortisol and CRP displayed satisfactory stability over 2 consecutive days and diurnal patterns of abrupt and gradual decline during the day, respectively. Controlling for baseline psychological measures and confounding variables, Cort_morn and diurnal cortisol slope was significantly and negatively associated with anxiety symptoms and positive affect 1 month later, respectively. Cort:CRP_even and Cort:CRP_morn was significantly and positively associated with depressive symptoms and sleep disturbance 1 month later, respectively.

CONCLUSION

These findings offer initial support for the prognostic utility of salivary cortisol and CRP and their balance as determinants of psychological health in healthy adults.