Starting from my own personal experience and extending into my professional practice as a psychotherapist, I’ve long been aware that managing stress is a crucial part of health and well-being, every bit as important as diet, exercise, sleep, and touch. But I’ve never known the scientific particulars of how stress works on the body, especially the brain, for better and for worse, until reading an article published in the latest issue of The Sun, an excellent literary magazine published in North Carolina that doesn’t accept advertising and is completely supported by its readers — the magazine equivalent of National Public Radio, without the big federal grants. Each issue contains a lengthy Q-and-A interview with someone who’s an authority on some important political, social, spiritual, or medical concern. The November 2016 issue presents an interview conducted by Jeanne Supin with Bruce Perry, a North Dakota-born Houston-based psychiatrist and researcher who has co-authored two books, The Boy Who Was Raised as a Dog and Born for Love: Why Empathy Is Essential — and Endangered. In this conversation, titled “The Long Shadow: Bruce Perry on the Lingering Effects of Childhood Trauma,” Perry gives the simplest, most thorough explanation I’ve ever read of how stress interacts with the human body.

The interview is long and interesting and worth seeking out in full. I’d like to share here a significant chunk specifically talking about stress. Here’s the gist of what he has to say.

On the harmful impact of chronic stress: “When you are overstressed, you no longer have efficient access to your higher brain functions. By the time you’re in a state of alarm, significant parts of your cortex – the highest-functioning part of your brain – have shut down entirely. This is adaptive if you’re confronted by a predator, because you don’t want to waste time thinking about how to respond: you want to fight or run away. But to do your best reasoning, you need access to that sophisticated part of your brain. To learn and plan, you need to be in a relatively calm state.”

On the healthy aspect of stress: “Resilience comes from stress. It’s important that parents, teachers, and coaches not be afraid of it. Exploring, getting dirty, and falling down help you build resilience and tolerate novelty and discomfort.”

To put those passages in context, read on, and let me know what you think.

Supin: Can you explain how our stress-response systems work?

Perry: All input – feelings of hunger or thirst, loud noises, the sound of someone’s voice, some information we learn – first enters the lower, more primitive part of our brains, which determines if this input is familiar or unfamiliar. If the input is familiar, it then travels to a higher, more evolved part of our brain, where we decide based on memory whether it’s good, bad, or neutral. If the input is unfamiliar, the brain’s default conclusion is This can’t be good. Any novelty – even desirable novelty, like learning something new – activates our stress-response system.

Some stress is actually good for us – for example, the stress related to meeting a new person or traveling to a new place. Predictable, controllable, and moderate activation of the stress-response system has been shown to build our capacity to manage challenges. When a child has the opportunity to challenge herself in the presence of supportive adults, it builds resilience. It’s the dose, the pattern, and the controllability that determine whether the stress is adaptive or harmful.

Let’s say you’re a six-year-old boy, and up until now your life has been OK. Mom and Dad split up, and there was some conflict around the divorce, but nothing too horrible. Then all of a sudden Mom has a new boyfriend in the house. That’s novel, so it generates moderate stress. At dinner he raises his voice at you; that’s unpredictable. He soon starts barking orders at you more frequently. He yells at your mom. He hits you, or he hits your mom. Your stress-response system doesn’t have time to return to baseline before another source of stress arrives. You start having anticipatory anxiety about what will happen next. Your baseline level of stress increases; things that would not have bothered you much before now bother you a lot. A harsh tone of voice that may have been mildly upsetting is now overwhelming. If the boyfriend’s behavior continues, your stress-response system may start to register any angry tone of voice as threatening. You’ve become what we call “sensitized.”

Conventional wisdom might suggest that the boy would get used to the angry, violent behavior and be less affected by it over time, but you’re saying the opposite is true.

Exactly. The more our stress-response system is activated in uncontrollable ways, the less able we are to handle even small amounts of stress.

When you are overstressed, you no longer have efficient access to your higher brain functions. By the time you’re in a state of alarm, significant parts of your cortex – the highest-functioning part of your brain – have shut down entirely. This is adaptive if you’re confronted by a predator, because you don’t want to waste time thinking about how to respond: you want to fight or run away. But to do your best reasoning, you need access to that sophisticated part of your brain. To learn and plan, you need to be in a relatively calm state.

Let’s go back to the six-year-old boy in your example. What happens to him at school?

The brain is good at generalizing from one kind of experience to another. Most of the time this ability is a gift, but this boy may generalize that all male authority figures who raise their voices are terrifying. This starts a vicious cycle: The boy arrives at school already on heightened alert due to his home situation, and he can’t pay attention. The teacher gets frustrated and raises his voice. The child is now even more on red alert. It’s impossible for him to concentrate. The rational parts of his brain shut down. Instead he has access only to the parts that process information valuable in threatening situations. He’s attuned to the teacher’s tone of voice, to whom the teacher is smiling at. He’s learning to read nonverbal cues. The calm child will learn the state capitals; the sensitized child will learn who is the teacher’s pet.

Can he recover from that?

Yes, opportunities for controlled, moderate doses of stress can shift these systems back toward well-regulated functioning. The key is that a moderate challenge for a typical child may be a huge challenge for a sensitized child.

The achievement gap in schools has a lot to do with the child’s home and community life if the family is concerned about not having money for food or rent or a doctor’s visit, that creates a pervasive sense of anxiety and unpredictability. The longer the child is in that environment, the worse the vicious cycle at school becomes. Eventually the kid says to himself, “There’s something wrong with me. I’m stupid.” And he drops out as soon as he can.

What about the character-building benefits of facing down adversity, of “rising to the challenge”? Is that ever applicable in these situations?

If you start from a healthy place, adversity can be character building. But if you grow up amid constant adversity, you are less likely to have the flexible and capable stress-response systems you need to face down adversity. Certainly many children do grow up with remarkable gifts and strengths despite their challenges, but when this happens, it’s often because there were people in the child’s environment who helped create a safe, predictable space for the child at least part of the time.

Are there instances in which well-intentioned parents protect their children from stress too much?

Yes, I’ve seen upper-middle-class children develop anxiety disorders because they had never been given the opportunity to explore the world. They’d been told only, “Don’t do this, don’t do that, don’t get dirty.” By the time these children went to preschool, they hadn’t learned to tolerate even slight discomforts. They became overwhelmed by the novelty of preschool and had meltdowns.

Resilience comes from stress. It’s important that parents, teachers, and coaches not be afraid of it. Exploring, getting dirty, and falling down help you build resilience and tolerate novelty and discomfort.

How might we apply this to whole communities?

First we have to understand that feeling connected to other people is one of our most fundamental needs. We feel safer when we are with kind and familiar people. Tension can arise from being part of a marginalized minority, whether you define that minority status by economics, race, ethnicity, religion, gender identity, sexual preference, or whatever. The marginalized group has a much higher level of baseline stress. It’s not a specific traumatic event; it’s a continuous sense of disconnection.

Our brain is constantly monitoring our environment to gauge whether or not we belong someplace. If we frequently get feedback that we don’t belong – or, worse, overt threats – then our body’s systems stay in a constant state of arousal. This increases the risk for diabetes and hypertension and makes learning, reflection, planning, and creative problem-solving harder. Over time it will actually change the physiology of your brain.

For example, for someone who already feels marginalized and is hypervigilant, even a relatively benign interaction, such as a police officer asking for your license, can trigger a volatile reaction. This is true for both the person being stopped and for the cop who’s doing the stopping. They both can be sensitized. People in law enforcement should know the principles of stress and trauma. It’s the key to understanding why some of their policies and behaviors have a destructive effect.