Cortisol is a hormone released by the adrenal glands in response to signals from the brain during times of stress. It's a key part of a feedback system in the brain addressing potentially dangerous situations. The connection between cortisol and stress explains why upsetting situations cause changes in the body. Due to high levels of cortisol in the bloodstream, chronic stress can have many bad effects on health, including depression and weight gain. The relationship between cortisol and stress can be positively changed by exercise and relaxation.
The corresponding rise of cortisol and stress comes from the hypothalamic-pituitary-adrenal axis (HPA). This is a feedback loop connecting emotional states like fear and stress to physiological responses like heart rate. The HPA axis modulates a very old process found in many different animals, called the fight-or-flight response. On discovering urgent danger, fear and stress lead to the temporary shutdown of bodily processes like digestion to concentrate energy on escaping from danger. Cortisol is the main hormone that causes the effects of stress.
When someone experiences anxiety and stress, the cortisol in the bloodstream rises. When this hormone is detected by receptors in the hippocampus, signals are sent to the hypothalamus. There, corticotropin-releasing hormone is secreted to activate the pituitary gland, which secretes adrenocorticotropic hormone (ACTH) into circulation. ACTH is the signal that tells the adrenal glands to make more cortisol and release it into the bloodstream. Cortisol causes many changes in tissues throughout the body to deal with emergency situations, including raising alertness and energy levels, reducing inflammation, and lowering pain sensitivity.
Over longer periods of time, the useful short-term relationship between cortisol and stress can impair health. Constant alertness can lead to high blood pressure, while digestive and thyroid function stay suppressed, slowing metabolism and increasing fat deposits and weight gain. Since cortisol suppresses the inflammatory response, chronic stress leads to slower wound healing. Cortisol reduces levels of the neurotransmitter serotonin, causing depression and diminished feelings of well-being. Depression also increases when cortisol interferes with the release of dopamine, a chemical important for feeling pleasure or joy.
Individuals secrete different levels of cortisol in response to stress, so not everyone experiences the same negative physical effects. Relaxation tempers the effects of cortisol. A great deal of research suggests that the proportional rise of cortisol and stress can be changed through exercise, meditation, or biofeedback. If chronic stress cannot be avoided, tempering its effects may provide a buffer against the negative health effects of persistently high cortisol circulation in the bloodstream. This is an important benefit of regular exercise.
