Understanding allostatic load and the long-term impact of stress

In 1993, Bruce McEwen and Eliot Stellar gave us their theory of allostatic Load. Allostatic load is the cost of ongoing exposure to elevated or fluctuating chronic hormonal responses caused by repeated acute and chronic stressors. It’s the cumulative burden of chronic stress over time, involving different physiological systems at varying degrees of activity, all working together.

Allostatic load is the wear and tear on the body which accumulates as an individual is exposed to repeated chronic stress responses.

McEwen and Stellar 1993

Allostasis is your body’s ability to adapt and maintain homeostasis. Homeostasis is any self-regulating process your body uses to maintain stability while adjusting to conditions that are best for your survival. You are programmed to cope with anything that threatens your body and mind’s safety and security at any level: physical, psychological, emotional, real, or perceived. From homeostasis — the starting point at which your body is in balance — to allostasis — the point at which you encounter stressors — you should be okay, as long as you allow sufficient recovery time after each stressor.

This recovery period gives your biology, physiology, and psychology time to rest, restore, and repair. In other words, as long as you give your parasympathetic nervous system (PNS) — your hormonal brake — time to return your body and brain to their original state of homeostasis, you should not reach an allostatic load.

Your body is constantly striving to adapt and restore balance. If you don’t allow sufficient recovery time between stressors, your brain will heighten your chronic stress response and automatically boost the production of the chronic stress hormone, cortisol.

This increase, coupled with less recovery time, results in more chronic stress responses and chronic stress hormones flooding your brain and body. Over time, this process establishes a higher baseline for your chronic stress responses and higher levels of chronic stress hormones.

If you cannot recover, if you prevent recovery, or if your recovery is insufficient, chronic stress will accumulate — layer upon layer, producing an overabundance of cortisol, a steroid hormone meant to protect you, but at this stage can only put your body, brain and mind into attack mode. This is allostatic load. While you may ignore the signs and symptoms of your chronic stress response, they will never ignore you.

Allostatic load occurs when your body, brain, and mind cannot cope with the persistent stress responses triggered by chronic stressors in your salient domains: home, family, work, health, finances, and community. It’s the cumulative impact of chronic stress hormones. We all have a threshold for stress, beyond which our bodies, brains, and minds become dysregulated. This dysregulation manifests as physical and mental health issues, including stress-related illness, depression, anxiety, and burnout.

Your body adapts to the conditions caused by your stress responses by producing and releasing stress hormones. These hormones help you adjust to these conditions; however, over time, they also lead to allostatic load, the wear and tear of your organs and brain. Understanding allostatic load will help you demystify the biology of your stress response by emphasising both the protective and damaging effects of your body’s attempts to cope with real and perceived stressors, as well as the resulting stress hormones.

In her book, Health Psychology: A Textbook (2012), Professor Jane Ogden explained that: “Stress-reactivity is when, confronted with the same stressor, some of us show stronger and longer physiological responses. In simple terms, some individuals react so intensely to stressors that their physiological activation is more pronounced and lasts considerably longer, and the production of stress hormones also endures for a significantly longer period, leaving them more susceptible to stress-related illnesses and burnout”.

Holahan, C. J., & Moos, R. H. (1990) investigated stress resistance and recovery. They stated: “Not all of us react to stressors in the same way, and some of us remain healthy, even when we’re faced with difficult stressors.” Stress resistance encompasses adaptive coping strategies, specific personality characteristics, and social support. It’s all about coping skills and strategies.

In normal circumstances, after a stress response, the parasympathetic nervous system (PNS) brings the body back to a “rest, restore and repair” state. However, some of us recover more quickly than others, while others have a slower rate of recovery. This is down to susceptibility to stress-related illness. Why? Because of the wear and tear of the brain and body caused by the chronic stress hormone, cortisol.

Research has shown that slower recovery from elevated cortisol levels can be linked to suppressed immune function and increased susceptibility to infection and illness. Stress reactivity, stress recovery, allostatic load, and stress resistance all influence our responses to stressors and our stress-illness link. When it comes to stress, one size never fits all.

In 1936, Hans Selye first described his General Adaptation Syndrome (GAS), but it wasn’t until the 1950s that his research defined the three-stage process of physiological changes our bodies undergo during a stress response: alarm, resistance and exhaustion/burnout.

In 1993, McEwen and Stellar’s theory of Allostatic Load explained how our bodies accumulate chronic stress hormones that drive physiological and neurological changes, overwhelming our bodies, brains, and minds and causing physical and mental illness.

Nowadays, if you ask your healthcare provider about Hans Selye’s 1950s General Adaptation Syndrome (GAS) – the three stages of our stress response, or McEwen and Stellar’s 1993 theory of Allostatic Load, which describes how, without sufficient recovery time, chronic stress hormones accumulate and cause physical and mental illness, they won’t have a clue what you’re talking about.

Today, as stress-related illnesses, anxiety, depression, and burnout continue to rise, it’s essential to remember what we’ve known since 1950 and 1993, namely that our physiological and neurological systems need adequate recovery time after each stress response to prevent these illnesses.

Taking a walk in nature, meditating, or simply sitting still and taking deep, slow belly breaths for at least three minutes, multiple times a day, are effective ways to lower cortisol levels. It’s so easy to do; why don’t you give it a try?

Read more of Joan Maycock’s articles on health: Inflammation: our best friend and worst enemy