Why Stress Causes Illness: A Quick Overview
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Why Stress Causes Illness: A Quick Overview

How stress causes illness: its physiological effects and the GAS model

We are no strangers to the stress of life. Anxieties dot the normal individual’s emotional landscape and become ensconced in our daily routine. Problems at the workplace can add up, and at the end of the day, even further difficulties at home can compound and wreak havoc to a person’s already exhausted psyche.

But studies have shown that it’s not the stressful event per se that can really damage our bodies, it’s actually the never-ending physiological responses that will be dangerous in the long run. It’s our stress response that is the real culprit, and by knowing more about the mechanisms that underlie it, the better we can cope and inoculate ourselves from the effects.

The Anatomy of Stressful Situations

What makes an experience stressful? By its very definition, it’s easy to point out that anything perceived to threaten a person’s well being is a stressor and will trigger a stress response. For one, it becomes threatening if a situation seems out of hand and beyond one’s control. Unpredictability characterizes stressful situations because the emotional load that uncertainty imposes on people can be too much. Given a choice between predictable and unpredictable aversive stimuli people find it more palatable if they could predict when the discomfort will start (Katz and Wykes, 1985). It’s the same as working with an uncooperative boss. If you’re working with a superior with a penchant for unpredictable aggressive outbursts, then most likely you’ll be on your guard all the time – a stressful situation indeed. But if you can predict when your boss will be staging his outbursts, then you can rest easy at those times that you know he won’t be out to get you.

An unprecedented or major life change, whether positive or negative can also be a source of stress. In a landmark study by Thomas Holmes and Richard Rahe (1967), they found that even positive events such as marriage or retirement could rank high up on the stress scale. This may be due to the fact that both events signal major changes in social structure and daily routine, i.e. living with a spouse, and experiencing life after daily work. Of course, the impact of negative events is stronger and is more debilitating than that of positive events (Holmes and Rahe, 1967; Taylor, 1991). This can also explain the original example about job loss and heart attacks; it just is too much to bear if you were suddenly laid-off.

In this case, we could now pinpoint what stressful situations could comprise. It should be perceived as uncontrollable, is unpredictable, and may even correspond to a major life change that is either expressed as a loss or a gain. But this wouldn’t be enough to explain how stress can result in illness. For sure, most individuals could weather a lot of stress because it simply is something that they could live with. What would be the tipping point, so to speak? This could be explained further by analyzing what happens to the body when a person is stressed.

The Physiological Effects of Responding to Stress

Imagine yourself in a dark, unfamiliar alley in the dead of the night. You briskly walk among the lights, senses tingling, scanning the surroundings for any form of threat. After a time in these dark surroundings, you may be able to hear your heart pumping rapidly, with the tempo of your breathing in conjunction with its rhythm. You feel your face flushed and your muscles tense, as if your whole body was preparing to act and respond quickly to anything.This, in fact, is called the fight-or-flight response, which has been touted as an evolutionary solution to matters that threaten an organism. Walter Cannon, a renowned physiologist, first described this condition in 1915 to explain the responses of animals to acute stress. He came to this realization while studying the digestive systems of animals because he noticed that they were not able to fully process food when exposed to stress. With this, Cannon resolved to investigate this mind-body connection.

Cannon’s work showed that physiological arousal from stress is caused by the activation of two systems, the sympathetic division of the autonomic nervous system and the adrenal-cortical system. Controlled by the hypothalamus, these two systems work in conjunction to prime the body for the fastest response. The sympathetic system swiftly acts to accelerate heart rate and elevate blood pleasure prepare the body for a big burst of activity. The adrenal-cortical system releases ACTH (adrenocorticotrophic hormone) through the pituitary gland, which in turn liberates other hormones (cortisol being the major hormone) that lead to physiological changes that will ready the organism to fight a threat or flee from it. It happens all in the span of an instant, with exhaustion the only cost to the over-all sequence of events. Thus, the organism’s survival is ensured.

We could obviously see how this is beneficial. For our ancestors who started out hunting for food in the wilderness, it is very important that they be able to act quickly to survive. Dozens of dangers punctuate human existence then, and it was necessary for such a response to evolve this way. The flight-and-flight response was heaven-sent and can be relied on when the going gets tough.

At least, this was then. The same automatic response that ensured our forefathers’ survival now wreaks havoc in ways more than one. Though threats have now been transformed to their more mundane counterparts, the result is still the same. The fight-or-flight response still elicits the same physiological changes even if the dangers are illusory or at least not life threatening, leading to health problems that we are better off not having. This is the connection between stress and illness.

The General Adaptation Syndrome Model

Hans Selye describes this process of responding to stress as the General Adaptation Syndrome (GAS) (Nolen-Hoeksema, 2008). Selye points out that in the presence of a stressor, all organisms undergo three phases of physiological changes. The first phase, alarm, constitutes the triggering the autonomic systems for fight or flight. The second phase, resistance, depicts the actual action that the organism chooses as a result of the stressful situation. The last phase, exhaustion, occurs if the organism is unable to act against the stress, resulting in the same loss of physiological resources that were commandeered to supposedly combat the threat.

Selye further explains that a prolonged, seemingly unending GAS cycle is the cause of physiological imbalances that result in a wide variety of illnesses. Based on his laboratory studies with animals exposed to different stressors, Selye saw significant changes in their bodily organs; stomach ulcers and enlarged adrenal glands are just some examples. In this light, it is highly disturbing how our bodies have been reacting to each stressful event we encounter. Multiply this a hundred times in a lifetime and we could see how alarming this is. The long-term effects of stressors can really damage health (Schneiderman et al., 2005).

In a 2006 study about job loss and older workers, it was found out that a displaced employee has twice the risk of having a heart attack compared to other employees (Gallo et al., 2006). This was due to the fact that these workers were too old to apply for other occupations, with the resulting psychological stress making them predisposed to illness. Recent studies also showed that this happens regardless of age (Strully, 2009) with the imposition of job loss being enough reason to result in later debilitating health conditions.

It was also found that stress hampers the immune system in animals and humans (Sergerstrom & Miller, 2004; Schneiderman et al., 2005) directly affecting the amount of lymphocytes (i.e. the killer cells that attack viruses) in the body. This now tells us that stress can make one predisposed to getting sick. This was shown in one experiment where, in a group of 394 volunteers exposed to 5 types of viruses and a saline solution, those who had higher stress levels in the past year were more susceptible to getting the common cold (Cohen et al., 1991). In a study of 47 people who survived the Northridge earthquake, it was also found that they have hampered regulation of natural killer t-cells (Segerstrom et al., 1998).

What is happening here? Apparently, we generally can’t get habituated to stressful situations. Though stress figures out a lot in the woes of daily living, its psychological response that seems to have a doubtful place in today’s world. It may prime us to respond and act quickly, but consistently doing so exacts a toll that’s more detrimental than the aforementioned benefit. Stress affects health, and in innumerable ways.


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Comments (1)

That's a well-written article supported by reliable findings. Great write.