The effect of an internet-based intervention for depression on cortisol and alpha-amylase

Introduction: Psychotherapeutic interventions for major depressive disorder (MDD) have been suggested to be associated with a normalization of biological stress system (i.e., the hypothalamic-pituitary-adrenal axis and the autonomic nervous system) dysregulation. Furthermore, pre-intervention cortisol parameters have been identified as prescriptive biological markers of treatment success. However, evidence of treatment effects on the biological stress systems is still sparse, and results are heterogeneous. The current study examined the effect of an internet-based intervention for MDD on salivary cortisol and alpha-amylase as well as hair cortisol concentrations. Moreover, the prescriptive capacity of pre-intervention cortisol and alpha-amylase concentrations on treatment response was explored. Methods: Thirty-eight participants suffering from mild to moderate MDD collected saliva and hair samples throughout the intervention. Biological outcome parameters were salivary cortisol and alpha-amylase (awakening response, total diurnal output, diurnal slope) and hair cortisol concentrations. Treatment response was indicated by change in depression severity and perceived chronic stress. Results: Treatment response on depression scores or chronic stress was not associated with changes in any of the cortisol or alpha-amylase parameters. Exploratory analysis indicated that non-responders showed a steeper alpha-amylase slope pre-intervention. Discussion: The results indicate that changes in depressive symptoms did not correspond to changes of the biological stress systems, contradicting the suggested normalization of dysregulated hypothalamic-pituitary-adrenal axis or autonomic nervous system activity through a psychotherapeutic intervention. However, the results point to a potential role of pre-intervention alpha-amylase slope as a prescriptive marker of treatment response for depression.