[Biomarkers of stress and fatigue]

A questionnaire based survey has been commonly used for the assessment of psychological stress and stress-related diseases. Development of a quantitative approach using a non-invasive sample (i.e., saliva, hair or nails) is highly desirable to measure chronic stress. This paper gives a brief explanation of subjective and objective (i.e., physiological signals, and biological markers) methods for stress assessment. Furthermore, it focuses particularly on the current knowledge about the biomarker candidates of chronic psychological stress and chronic fatigue syndrome (CFS). Psychological stress is known to stimulate the autonomic nervous, endocrine, and immune systems. Since chronic stress is associated with suppression of a variety of immune parameters, some immune markers are potentially useful.