Validation of a new method for saliva cortisol testing to assess stress in first responders.

Background: Acute or chronic stress can lead to physical and mental disorders. Measuring cortisol can objectify the degree of stress. Cortisol is traditionally measured in serum, but recently the relevant fraction of free cortisol can be reliably measured in saliva, using the very sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method.