Measuring Salivary Cortisol to Assess the Effect of Natural Environments on Stress Level in Acute Patients With Severe Brain Injuries: An Exploratory Study.

Background: Salivary cortisol is a safe and non-invasive measure of hypothalamic-pituitary-adrenal axis function and is used as a biomarker of the human stress response. Natural environments are recognized to contribute to help reduce the effect of stress.

Objective: To determine the feasibility of a salivary cortisol collection protocol for acute severely brain-injured patients, and to explore the influence of exposure to natural settings on salivary cortisol concentration as an index of stress level.