Cortisol and alpha-amylase assessment in psychotherapeutic intervention studies: A systematic review.

Dysregulations of the hypothalamus-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS), two of the most prominent stress-responsive systems, have been associated with the development and maintenance of various mental disorders. It has been suggested that these alterations might normalize in the course of psychotherapeutic interventions. We conducted a comprehensive review of psychotherapeutic intervention effects on HPA axis and ANS regulation in adult samples with mental disorders. We searched four databases for psychotherapeutic intervention studies with mentally ill patient samples, assessing cortisol and/or alpha-amylase before and after treatment. Study quality and confounder consideration within biomarker assessment were examined. Twenty-five studies were included. Psychotherapeutic interventions and biomarker assessment methodology varied substantially between studies. Accordingly, meta-analytical computations were deemed unfeasible. Study characteristics especially regarding cortisol and alpha-amylase assessment and analysis procedures were comprehensively reviewed. Study quality and biomarker confounder consideration ratings were mostly moderate to strong. Based on the results, we provide recommendations regarding intervention design and biomarker assessment methodology to increase comparability of psychotherapeutic treatment effects in future studies.