A new way to think about stress and health

by Joseph Fridman

You’ve probably been taught that the human body is like a thermostat: It measures whether something is above or below a certain set point, and if so, will employ some tactic to return it to its set point. For example, if it’s too hot, the body sweats to cool off — too cold, and the body will shiver to warm back up. The theory extends to other physiological features like blood pressure and blood sugar. This process — detecting a change and returning the body to some baseline — is called homeostasis, which comes from the Greek words for “the same” and “standing still.” Homeostasis, like the thermostat, is all about maintaining equilibrium, constancy, and stability.

But some experts argue that this theory of the human body is incorrect.

In a 1981 paperneuroscientist Peter Sterling and epidemiologist Joseph Eyer, from the University of Pennsylvania, argued that “chronic arousal” was the source for the negative health effects associated with stress. Being aroused all the time caused the brain to “mobilize the mechanisms that produce energy for coping and suppressing the mechanisms that store energy” and let the body grow and repair. The duo hypothesized that the human body wasn’t striving to be stable, to meet a set point, like a particular blood pressure. Rather, it uses incoming sensory information to estimate the body’s state and anticipate what will happen next. If a demanding situation is predicted, then the brain marshals the body’s resources — changing blood pressure, secreting hormones, metabolizing glucose, and so on — to begin to meet those needs before they arise. It could explain why people who experience high levels of stress due to social issues like financial hardship, divorce, or racism, also have higher rates of diseases likehypertension, cancer, coronary disease, and, ultimately, earlier death.

Sterling and Eyer’s idea was revolutionary: The brain wasn’t controlling the body to react to the world. It was predicting the future and preparing the body for it. They named this concept allostasis, and it quickly found purchase among scientists who study stress.

The idea of allostasis has also revolutionized the understanding of why people have brains in the first place. As Lisa Feldman Barrett, a neuroscientist and Northeastern University distinguished professor, explains, “Brains did not evolve to think or feel. Brains evolved to regulate bodies.”

“Just like companies that have a financial office for making sure that their overall budget is balanced, your brain manages the budget for all the accounts in your body.”

In her recent book How Emotions are Made: The Secret Life of the Brain, Barrett introduced a new metaphor for allostasis, describing it as a “body budget.”

“Just like companies that have a financial office for keeping track of their accounts and making sure that their overall budget is balanced, your brain manages the budget for all the accounts in your body, keeping track of water, salt, glucose, and other resources that keep a person alive and well,” she says. Like a monetary budget, a body budget isn’t meant to remain at a single cash value. To maintain good health over the long term, a brain must make additional investments in glucose and other metabolic resources for other activities such as upkeep, learning, exercising, socializing, and de-stressing.

Barrett explains that “like a financial budget, a body budget can run a deficit, and over the long term, a bankrupt body budget results in illness.” Sometimes your budget might dip into the red as the result of a big, unexpected expenditure: exposure to a serious infection, pulling an all-nighter, or experiencing a traumatic event. In other persistent cases (like being subjected to bullying, racism, or sexism), debts compound over time. Either way, when your body budget is overdrawn for too long, your immune system gets involved and you get sick. Chronically overtaxed body budgets set the stage for chronic illness.

Depression, for example, can be thought of as a body budget that is bankrupt. “What happens when a brain is deeply in debt?” Barrett asks. “It stops spending. And what are the two most expensive things that a brain can do? Learning something new. And moving its body.” Barrett also suggests that disrupted body budgets may be at the heart of neurodegenerative diseases like Alzheimer’s disease.

Together with colleagues from Massachusetts General Hospital and Harvard Medical School, Barrett’s lab has found evidence for a network of neurons in the human brain that maintains allostasis by predictively managing its body budget. This network is important for remembering, emoting, decision-making, and a host of other psychological functions. Dysfunctions and degeneration in this network are not just linked to depression and Alzheimer’s disease, but to many other illnesses such as diabetes, as well as chronic stress, obesity, and addiction.

Sterling and Barrett agree: The brain is always making predictions about the state of the body in an effort to maintain an efficient and smoothly-running metabolism. And when that prediction machine goes off the rails, so does your health. Barrett suggests that one way to stay on the straight and narrow, health-wise, is to take your body budget seriously and regularly get enough sleep, exercise, and nutrition. “Even leaving your phone in another room while you’re sleeping is an excellent start,” she says.

Not all of us are afforded an equal path to good health, unfortunately.Financial deficits can create biological deficits, and vice versa, creating a vicious downward spiral. Social tension drives hypertension, creating more social stress, according to Sterling. It is no surprise, then, that metabolic illnesses and mood disorders are on the rise as Americans are experiencing record rates of income inequality and political polarization.

As an antidote, Sterling argues that society needs to “recognize that pharmacology cannot be the primary route to health.” Symptoms of social malaise cannot be alleviated with pills alone. In his forthcoming bookWhat is Health?: Allostasis and the Evolution of Human Design, Sterling argues that health is a state of “optimal responsiveness,” one that cannot be reached by interventions that decrease the capacity to adapt, like drugs. Instead, Sterling believes that biological conditions have social, political, and cultural solutions.

If the idea of allostasis and the predictive brain is to be taken seriously, then everyone needs to invest in their own body budgets, and the budgets of others. It is not enough to treat disease and disorder on the individual level. Systemic fixes are needed — ones that address chronic arousal and social stress. The health of our bodies and our body politic are intertwined. As Rudolf Virchow, the father of social medicine, wrote, “Medicine is a social science, and politics is nothing else but medicine on a large scale.”

Originally published by Joseph Fridman for Elemental on Medium.


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