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Health Protocols

Stress Management

How Does The Body Respond to Stress?

The Fight or Flight Response

Stress generally occurs when external stimuli disturb the dynamic balance of the body’s physiological processes.7 The stress, or “fight or flight,” response begins in the brain, where the perception of a threat triggers the release of corticotropin releasing hormone (CRH) from the region called the hypothalamus. This stimulates the anterior pituitary, a gland that sits just under the hypothalamus, to increase release of adrenocorticotropic hormone (ACTH) into the bloodstream. ACTH then acts on the adrenal cortex, raising production and release of cortisol and the less active glucocorticoid, corticosterone, as well as another adrenal hormone called dehydroepiandrosterone, or DHEA.8

Stress Response System

The signaling network between the nervous system and adrenal glands is called the hypothalamic-pituitary-adrenal (HPA) axis and is regulated in part by a negative feedback mechanism, through which rising blood levels of cortisol inhibit release of both CRH and ACTH.3,9

Stress also directly engages sympathetic nervous system signaling in the brain region called the locus coeruleus. Catecholamine neurohormones (epinephrine and norepinephrine, also known as adrenaline and noradrenaline) released by the adrenal medulla and sympathetic nerve endings have physiologic effects intended to help the body respond and adapt to stressful circumstances. Although it tends to work in concert with the HPA axis, the sympathetic nervous system also functions independently to activate the stress response.3,9

Acute Stress

As mediators of the stress response, cortisol and catecholamines have profound effects throughout the body (see Table 1). When acutely elevated, they help prepare the body to escape danger. For example, cardiac output increases to support stronger blood flow; blood sugar levels increase to meet higher energy demands; pupils dilate to allow for greater visual input; alertness and cognition are enhanced; and digestive and reproductive functions are inhibited due to their not being essential in the short term.9

Table 1: Hidden Causes of Acute Stress

Physiological Stressor

Acute Adaptive Stress Response

Low blood glucose level10,11

Catecholamines stimulate breakdown of carbohydrate stores and conversion of protein and fat into glucose

Cortisol inhibits glucose use by non-central nervous system tissue

Low blood pressure3,12

Catecholamines stimulate constriction of blood vessels

Cortisol increases sodium and water retention in the kidneys

Low oxygen saturation3,13,14

Catecholamines stimulate the respiratory center of the brain to increase breathing, increase heart rate and contraction strength, and selectively constrict blood vessels

Oxidative stress15

Catecholamines and cortisol alter cell metabolism to restore reductive-oxidative balance

Inflammatory cytokines1,16

Catecholamines and cortisol modulate immune activities

Chronic Stress

The acute stress response can lead to positive adaptive effects, but when the HPA axis and locus coeruleus are chronically activated, their effects become maladaptive: the response to a chronic or repeated stress may become dull, yet, at the same time, sensitivity to new stressors may be enhanced.12,17 A dysregulated stress response results in altered patterns of cortisol and catecholamine production and/or receptor response to them.3,9 Chronic stress may even alter brain structure.18 In addition, impairment of the HPA axis due to chronic stress appears to suppress DHEA production and release, even under acutely stressful circumstances.8,19 This is important because DHEA opposes some of the actions of cortisol: it protects nerves and stimulates development of neuronal connections, has immune-regulating effects that oppose and balance those of cortisol, and may prevent cortisol-induced metabolic disturbances.8 The exact nature of the response to chronic stress depends on individual characteristics such as personality traits, gender and age, life experiences, and genetic and epigenetic factors.3

The Stress Burden of Social Isolation and Loneliness

In January 2018, the British government announced the establishment of a Ministry of Loneliness. The decision was based on a 2017 report finding that 9 million Britons often or always feel lonely and the growing recognition that social isolation and loneliness take a toll on physical and mental health.20,21

The evidence for links between loneliness, a form of psychological stress, and poor health is particularly strong for cardiovascular disease and mental health problems.20-23 In older adults in particular, loneliness has been linked to increased cognitive decline and dementia, health care use, nursing home admissions, and mortality.21 A recent review of the research noted the health effects of loneliness may be mediated by altered HPA axis and sympathetic nervous system reactivity to stress. Like the stress response itself, the reaction to social isolation appears to vary among individuals.24