Allostatic Load: Stress Upon Stress

Chronic stress is a potentially lethal condition that is characterized by long duration and effect accumulation. Humans respond to stressors such as physical or perceived danger, an infection, or a crowded and noisy environment, by initiating a complex biopsychosocial adaptation and coping response. This response is initiated by the sympathetic nervous system and leads to release of excitatory stress hormones (the catecholamines) and glucocorticoids from the adrenal cortex (the well-known adrenaline rush).

The objective of this rapid physical mobilization of the body’s resources is to engage with the stressor, resolve it and return to a more normal state of alertness. Regaining normal arousal levels through a response and adaptation to the stressor is called allostasis. A highly stressed state is meant to be temporary and to subside naturally when the challenge has passed.

There is never a shortage of situations that trigger the stress reaction, at work or at home. All of us face the not too uncommon challenge of having to cope with more than one stressor at once or a series of stressors that happen within a relative short time. Most individuals can cope with this type of demands and are able to regain allostasis once the stressor or stressors have been taken care of or have taken care of themselves.

When individuals are not able to cope effectively with the stressor and cannot regain allostasis, this creates an accumulation of allostatic load. In this situation, there is an incomplete return to the normal condition and a regaining of physical and emotional stability. In fact, a state of stress at relatively high levels becomes the “new normal.” Over many weeks, months, or even years, this exposure to elevated levels of stress hormones can produce allostatic overload, with predictably serious health consequences.

Type 1 Allostatic Load

If the physical and emotional energy required to meet the demands created by one’s cumulative allostatic load routinely exceeds the energy intake and what can be mobilized from one’s own resources, type 1 allostatic overload occurs.

Allostatic overload type 1 is characterized by a significant increases in the circulation of glucocorticoids in the bloodstream (and other hormones that regulate allostasis), which triggers physiological and behavioral changes. These changes refocus the individual from functioning at normal levels of stress in daily routines into a high-stress high-alert survival mode.

Type 2 Allostatic Load

If energy demands are not exceeded and the individual continues to take in or store as much or even more energy than he/she needs—perhaps as a result of stress-related food consumption, choice of a fat-rich diet, or metabolic imbalances (prediabetic state) that favor fat accumulation—then type 2 allostatic overload occurs.

Allostatic overload type 2 causes lesser but higher than normal levels of glucocorticoids (and other hormones that regulate allostasis), which do not trigger physiological and behavioral responses, in such a way the individual remains stuck in a situation of high allostatic load without resolution.

Allostatic Load and Its Consequences

Elderly people who have had a lifetime of sustained economic hardship can have a more rapid decline of physical and mental functioning.  Hypertension is often an indicator of job stress, particularly in factory workers, in other workers with repetitive jobs and time pressures, and in workers whose jobs were unstable due to financial and market conditions.

In certain societies, conflict and social instability have been found to increase illness and mortality. For example, cardiovascular disease was found to be a major contributor to the almost 40% increase in the death rate among Russian males in the social upheaval which followed the fall of Communism. High blood pressure causes atherosclerosis as well as increased risk for heart attacks.

Abdominal obesity is another stress-linked change, which is often a precursor to more serious illness such as diabetes. The immune system is also a likely target of psychosocial stress, increasing vulnerability to the common cold and other more serious infections.