Stress has three components: (1) inputs (external factors, such as the presence of a stressor in the environment), (2) processes (internal factors, such as a predisposition to experiencing a stress response), and (3) outputs (biological responses).
Stress responses occur at two pathways in the body.
A rapid response occurs at the sympathetic-adrenal medullary (SAM) pathway. The sympathetic nervous system (SNS) is activated and triggers the release of neuromodulators called catecholamines from the adrenal glands. Catecholamines act as signals which have wide-ranging effects on the human body, such as increased heart rate and oxygen consumption.
In contrast, a slow response occurs at the hypothalamic-pituitary-adrenal (HPA) pathway. Corticotropin-releasing hormone (CRH) is released from the hypothalamus. CRH triggers release of adrenocorticotropin (ACTH) from the pituitary gland. In turn, ACTH triggers release of a hormone called cortisol from the adrenal glands. Cortisol leads to changes in the body, including an increase in the production of glucose (prolonging the effects of catecholamines) and suppression of the immune system.
From an evoluntionary standpoint, stress produces a physiological response (fight-or-flight) in the body appropriate to the situation at hand, which enabled our ancestors to survive in aversive events.
The body is unable to distinguish between the stressors faced by our ancestors and modern stressors, and mounts a physiological response regardless. Both short-term (acute) and long-term (chronic) responses to stress have significant consequences in the body and may lead to diabetes, high blood pressure, depression, and/or anxiety.
There are two hypotheses.
The vulnerability hypothesis states that the brain is more vulnerable to toxins following chronic stress.
On the other hand, the glucocorticoid hypothesis argues that overexposure to glucocorticoids in the frontal lobe and hippocampus of the brain leads to deterioration in these areas.
Two approaches are currently being examined in our lab: mindfulness-based stress reduction (MBSR) and MTM.
MBSR is a stress reduction technique adapted by Dr. Kabat-Zinn. It is rooted in Eastern spiritual practices and focuses on being aware of the present moment. MBSR has been found to be beneficial in the management of both physical and mental health, and we are currently examining the effect of MBSR on stress and aging.