Hair cortisol, stress exposure, and mental health in humans: A systematic review

The effect sizes are calculated when descriptive statistics are provided, to enable preliminary comparisons across the different laboratories. For exposure to chronic stressors, the effect sizes on hair cortisol levels were medium to large, whereas for psychopathology, the effect sizes were small to medium. This is a first implication that the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis in the development and/or maintenance of psychopathology may be more subtle than it is in healthy but chronically stressed populations. Future research possibilities regarding the application of hair cortisol research in mental health and the need for multidisciplinary approaches are discussed.