24 Jul The Science of Stress and How Our Emotions Affect Our Susceptibility to Burnout and Disease
For nearly three centuries, the idea that our emotions could impact our physical health remained scientific taboo — setting out to fight one type of dogma, Descartes had inadvertently created another, which we’re only just beginning to shake off. It was only in the 1950s that Austrian-Canadian physician and physiologist Hans Selye pioneered the notion of stress as we now know it today, drawing the scientific community’s attention to the effects of stress on physical health and popularizing the concept around the world. (In addition to his scientific dedication, Selye also understood the branding component of any successful movement and worked tirelessly to include the word itself in dictionaries around the world; today, “stress” is perhaps the word pronounced most similarly in the greatest number of major languages.)
But no researcher has done more to illuminate the invisible threads that weave mind and body together than Dr. Esther Sternberg. Her groundbreaking work on the link between the central nervous system and the immune system, exploring how immune molecules made in the blood can trigger brain function that profoundly affects our emotions, has revolutionized our understanding of the integrated being we call a human self. In the immeasurably revelatory The Balance Within: The Science Connecting Health and Emotions, Sternberg examines the interplay of our emotions and our physical health, mediated by that seemingly nebulous yet, it turns out, remarkably concrete experience called stress.
The relationship between memory, emotion, and stress is perhaps the most fascinating aspect of Sternberg’s work. She considers how we deal with the constant swirl of inputs and outputs as we move through the world, barraged by a stream of stimuli and sensations.
Memory, it turns out, is one of the major factors mediating the dialogue between sensation and emotional experience. Our memories of past experience become encoded into triggers that act as switchers on the rail of psychoemotional response, directing the incoming train of present experience in the direction of one emotional destination or another.
This is where stress comes in — much like memory mediates how we interpret and respond to various experiences, a complex set of biological and psychological factors determine how we respond to stress. Some types of stress can be stimulating and invigorating, mobilizing us into action and creative potency; others can be draining and incapacitating, leaving us frustrated and hopeless. This dichotomy of good vs. bad stress, Sternberg notes, is determined by the biology undergirding our feelings — by the dose and duration of the stress hormones secreted by the body in response to the stressful stimulus.
As soon as the stressful event occurs, it triggers the release of the cascade of hypothalamic, pituitary, and adrenal hormones — the brain’s stress response. It also triggers the adrenal glands to release epinephrine, or adrenaline, and the sympathetic nerves to squirt out the adrenaline-like chemical norepinephrine all over the body: nerves that wire the heart, and gut, and skin. So, the heart is driven to beat faster, the fine hairs of your skin stand up, you sweat, you may feel nausea or the urge to defecate. But your attention is focused, your vision becomes crystal clear, a surge of power helps you run — these same chemicals released from nerves make blood flow to your muscles, preparing you to sprint.
All this occurs quickly. If you were to measure the stress hormones in your blood or saliva, they would already be increased within three minutes of the event. In experimental psychology tests, playing a fast-paced video game will make salivary cortisol increase and norepinephrine spill over into venous blood almost as soon as the virtual battle begins. But if you prolong the stress, by being unable to control it or by making it too potent or long-lived, and these hormones and chemicals still continue to pump out from nerves and glands, then the same molecules that mobilized you for the short haul now debilitate you.
These effects of stress exist on a bell curve — that is, some is good, but too much becomes bad: As the nervous system secretes more and more stress hormones, performance increases, but up to a point; after that tipping point, performance begins to suffer as the hormones continue to flow. What makes stress “bad” — that is, what makes it render us more pervious to disease — is the disparity between the nervous system and immune system’s respective pace. Sternberg explains:
The nervous system and the hormonal stress response react to a stimulus in milliseconds, seconds, or minutes. The immune system takes parts of hours or days. It takes much longer than two minutes for immune cells to mobilize and respond to an invader, so it is unlikely that a single, even powerful, short-lived stress on the order of moments could have much of an effect on immune responses. However, when the stress turns chronic, immune defenses begin to be impaired. As the stressful stimulus hammers on, stress hormones and chemicals continue to pump out. Immune cells floating in this milieu in blood, or passing through the spleen, or growing up in thymic nurseries never have a chance to recover from the unabated rush of cortisol. Since cortisol shuts down immune cells’ responses, shifting them to a muted form, less able to react to foreign triggers, in the context of continued stress we are less able to defend and fight when faced with new invaders. And so, if you are exposed to, say, a flu or common cold virus when you are chronically stressed out, your immune system is less able to react and you become more susceptible to that infection.
Extended exposure to stress, especially to a variety of stressors at the same time — any combination from the vast existential menu of life-events like moving, divorce, a demanding job, the loss of a loved one, and even ongoing childcare — adds up a state of extreme exhaustion that leads to what we call burnout.
But stress isn’t a direct causal function of the circumstances we’re in — what either amplifies or ameliorates our experience of stress is, once again, memory. Sternberg writes:
Our perception of stress, and therefore our response to it, is an ever-changing thing that depends a great deal on the circumstances and settings in which we find ourselves. It depends on previous experience and knowledge, as well as on the actual event that has occurred. And it depends on memory, too.
The most acute manifestation of how memory modulates stress is post-traumatic stress disorder, or PTSD. For striking evidence of how memory encodes past experience into triggers, which then catalyze present experience, Sternberg points to research by psychologist Rachel Yehuda, who found both Holocaust survivors and their first-degree relatives — that is, children and siblings — exhibited a similar hormonal stress response.
This, Sternberg points out, could be a combination of nature and nurture — the survivors, as young parents for whom the trauma was still fresh, may well have subconsciously taught their children a common style of stress-responsiveness; but it’s also possible that these automatic hormonal stress responses permanently changed the parents’ biology and were transmitted via DNA to their children. Once again, memory encodes stress into our very bodies. Sternberg considers the broader implications:
Stress need not be on the order of war, rape, or the Holocaust to trigger at least some elements of PTSD. Common stresses that we all experience can trigger the emotional memory of a stressful circumstance — and all its accompanying physiological responses. Prolonged stress — such as divorce, a hostile workplace, the end of a relationship, or the death of a loved one — can all trigger elements of PTSD.
Among the major stressors — which include life-events expected to be on the list, such as divorce and the death of a loved one — is also one somewhat unexpected situation, at least to those who haven’t undergone it: moving. Sternberg considers the commonalities between something as devastating as death and something as mundane as moving:
One is certainly loss — the loss of someone or something familiar. Another is novelty — finding oneself in a new and unfamiliar place because of the loss. Together these amount to change: moving away from something one knows and toward something one doesn’t.
An unfamiliar environment is a universal stressor to nearly all species, no matter how developed or undeveloped.
In the remainder of the thoroughly illuminating The Balance Within, Sternberg goes on to explore the role of interpersonal relationships in both contributing to stress and shielding us from it, how the immune system changes our moods, and what we can do to harness these neurobiological insights in alleviating our experience of the stressors with which every human life is strewn.
Originally posted at brainpickings.org