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CORTISOL CIRCADIAN RHYTHM AND HUMAN PSYCHOPHYSIOLOGICAL ACTIVITY

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Ciarkowska W.

Psychologia-Etologia-Genetyka

2006

vol. 13

9-33

The paper gives an overview of cortisol, stress hormone - its physiological functions, circadian rhythm and relationship with stressful situations. Cortisol plays a critical role in metabolism by mobilizing energy resources (this hormone elevates blood glucose levels). Cortisol circadian rhythm is characterized by acrophase in the morning (9 a.m.), after awakening. Psychological stressors increase cortisol levels, particularly when tasks were uncontrollable or characterized by social-evaluative threat (task performance could be negatively judged by others). Cortisol augmentation peaks about 15 min. after stressor and recovery time to basal level takes about one hour. Cortisol is an important regulator of many physiological rhythms, e.g. sleep - wakefulness and immune system. There is strong evidence that cortisol can suppress the immune response and consequently, the release of more cortisol under stress is associated with greater susceptibility to infectious agents. It seems therefore, that morning hours could be the time of day when the vulnerability to viruses or bacteria is particularly high. Studies on cortisol responses during stressors in naturalistic conditions (work overload, shiftwork, familial and marital problems, chronic somatic disease) revealed that the change of typical diurnal rhythm is the most pronounced effect (acrophase in the afternoon or during night, 'blunted' rhythm, i.e. too small amplitude or rhythm amplitude too great than typically).

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1 Psychologia-Etologia-Genetyka

1 Ciarkowska W.

1 2006

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CORTISOL CIRCADIAN RHYTHM AND HUMAN PSYCHOPHYSIOLOGICAL ACTIVITY