Nadine Burke Harris on the Physical Effects of Toxic Childhood Stress

Dr. Nadine Burke Harris is a pediatrician, mother and the founder and CEO of San Francisco’s Center for Youth Wellness. Her experience treating children who had suffered extreme trauma led her to write The Deepest Well: Healing the Long-Term Effects of Childhood Adversity. In the book, she digs into the connections between adverse childhood experiences, toxic stress and lifelong illness. The Deepest Well covers her investigation of more than 17,000 adult patients’ childhood experiences of divorce, substance abuse, neglect and more, and her breakthrough discovery that childhood stress changes our neural systems and affects our health over our lifetimes. In this interview, we discuss the connection between psychological stress and physical health, as well as specific health interventions that can alleviate toxic stress. Interested readers can enter to win a hardcover copy of The Deepest Well in the giveaway at the end of this interview.

Greg: What is an adverse childhood experience?

Nadine: The term “adverse childhood experience” (ACE) comes from the groundbreaking research that was done by the CDC and Kaiser Permanente. They looked at ten specific categories, which include physical, emotional and sexual abuse, physical and emotional neglect, or growing up in a household where a parent was mentally ill, substance-dependent or incarcerated, or there was parental separation or divorce or domestic violence. And what’s really important about these ACEs was that the greater number you’ve been exposed to, the greater the risk for serious health problems, like heart disease, stroke and cancer.

Greg: What are some of the other effects of ACEs?

Nadine: So that’s been the focus of my research: understanding how childhood adversity affects our brains and bodies. And it ultimately has to do with the overactivity of our stress response—something called a toxic stress response. If our stress response gets activated too frequently, it can lead to long-term problems. For example, folks who have high doses of adversity have a higher risk of arthritis. But ultimately the way it works has to do with a stress response that is overactive. I think in real time how that can look and feel to people is being quick to anger or having trouble controlling their impulses or getting sick easily when they feel overwhelmed.

Nadine Burke Harris
Nadine Burke Harris

Greg: You said the frequency of ACEs increases the likelihood of developing a toxic stress response later in life. Are there other factors that would increase the likelihood of developing a toxic stress response?

Nadine: Absolutely. It’s both nature and nurture. Some of it has to do with individual vulnerability, and some of that can be genetic. But one of the things we’re understanding now is that the relationships we have play a huge role. In the presence of a buffering caregiver, many kids can actually not go on to develop a toxic stress response but have what’s called a tolerable stress response, which is when the body’s stress response gets activated to a certain degree and then it goes back to normal. 

We’re now understanding the profound impact that relationships have on affecting whether or not adversity leads to long-term health problems. Sometimes that relationship is with a grandparent, sometimes it’s a teacher, sometimes it’s an auntie or an uncle. As long as it’s an adult who is spending significant time with a child and is able to be that well-regulated caregiver providing that stable relationship. But the real piece is the strength and stability of the relationship.

Greg: What about the intensity of the adverse experience or the child’s socioeconomic status? Do those factors play a role?

Nadine: So the more frequent the adversity, the more intense the adversity, the greater risk that a child will develop toxic stress. Socioeconomic status is both the chicken and the egg. One of the things we see from the data is that there’s a higher prevalence of childhood adversity in low socioeconomic status groups. We also see that ACEs happen at every socioeconomic level. None of us is spared. But the thing that’s really challenging is that oftentimes kids who are in low socioeconomic groups also have fewer resources. They may be less likely to have a caregiver who is not so overwhelmed by their own history of adversity or the current struggles that are going on in their lives that they’re able to be a buffer. So what we see is that low socioeconomic groups are particularly at risk. 

But this doesn’t just happen in low-income neighborhoods, and I think for some of us it’s a lot easier to think about it that way. Like, “Oh, it’s those folks,” or “It happens there.” The research shows that’s not true. Even the original research done by the CDC shows that two-thirds of the population have experienced at least one ACE, and that population was seventy percent college-educated and seventy percent Caucasian.

Greg: What are some of the other physical effects of toxic stress, besides the ones you mentioned?

Nadine: Essentially when our stress response becomes overactive, a couple of things happen. Number one, it activates the brain. That’s a very important part of the stress response that makes us more alert and all that good stuff. The other thing is that it affects our hormones, things like cortisol and adrenaline. And that’s good in the short term, but when you have really high doses or when you have too much exposure to high levels of cortisol and adrenaline, that can be harmful. And when you activate your stress response, it also activates your immune system. If you’re in a forest and you’re fighting a bear and he gets his claws into you, you want your immune system to be primed to bring inflammation to stabilize the wound. Again, that’s good in the short term but in the long term, too much inflammation is bad for our bodies. 

There are also some ways in which early adversity changes the way our DNA is read and transcribed, which can change the way all of those body systems that I just talked about respond to stress in the long term. So when we look at the ten leading causes of death in the United States, early adversity or ACEs dramatically increase the risk for seven out of ten of the leading causes: heart disease, cancer, stroke, chronic obstructive pulmonary disease, diabetes, Alzheimer’s and suicide.

Greg: So is it a matter of individuals not being able to turn off the stress response? Or is it that once toxic stress is initiated, individuals will respond more dramatically to future stress?

Nadine: Both. With the stress response, you have something called feedback inhibition. Your stress response is activated and it creates all these cascades in your body. The end product—either cortisol or adrenaline—shuts the whole process off at a certain level. When kids are exposed to high doses of adversity, that feedback loop doesn’t work as well. So it’s harder to shut off and because of some of the changes in the DNA, the body can be wired to respond more significantly, to release higher levels of stress hormones with subsequent activation of the stress response. And the part of the brain that identifies scary or stressful things can also start to misfire. So someone may be activated by something that actually isn’t threatening to them but is similar to something they’ve been exposed to in the past.

Regular exercise helps to metabolize stress hormones and improves neurologic functioning.

Greg: In your book, you discuss several approaches to reducing stress and healing from ACEs, including nutrition and exercise. Would nutrition and exercise just manage the physical symptoms of stress? Or do they go beyond the physical symptoms and start to work on the stress response as well?

Nadine: Both. Regular exercise helps to metabolize stress hormones, but it also releases things like endorphins, which are the feel-good hormones that kind of do the opposite of what a lot of stress hormones do. Regular exercise also improves neurologic functioning. The brain is one of the big things that is affected by childhood adversity, and regular exercise can actually enhance what we call neuroplasticity, or the way the brain cells talk to each other. Moderate exercise is also good for the immune system, and regular exercise is also associated with reduced risk for some of the DNA changes that we see with stress. And similarly with nutrition: diets that are rich in lean proteins, that avoid high-sugar, high-fat foods, that have omega-3 fatty acids, can help to reduce stress hormones, reduce inflammation and enhance neuroplasticity.

Greg: Are there any specific diets you recommend?

Nadine: This is something I would recommend folks talking about with a nutritionist. There are certain diets that are specifically anti-inflammatory diets, and that could certainly be helpful because inflammation is one of the important factors in toxic stress and how it affects our health.

Greg: What about exercise? Are there specific exercise protocols you recommend?

Nadine: It’s not specific forms of exercise when we look at the data. “Breaking a sweat an hour a day” is how most of the research studies characterize how much and what type of exercise is important. Now there are also certain types of exercise that incorporate a mindfulness component, like yoga, so you’re doing a little bit of double duty there.

Greg: I imagine variety would probably be important. You could break a sweat by running for an hour every day, but I imagine that would also create a stress response.

Nadine: So you don’t want to be an ultramarathoner. If you run fifty miles, that actually increases your cortisol levels. But if you have a moderately paced jog, the data actually suggests that helps you reduce stress hormones overall.

Greg: So as long as the volume is not too high and you’re able to recover afterward?

Nadine: That’s exactly right.

Greg: This could start to seem like a lot—diet, exercise, sleep, mindfulness, relationships. What exactly would a comprehensive treatment program for ACEs look like?


Nadine: It sounds like a lot, but it’s really an approach. I liken this connection between ACEs and this new understanding about how childhood adversity can lead to lifelong health problems to germ theory. If you were the first person thinking “Oh my God, germs are the things that cause infection,” and you were trying to approach that problem, it would seem like a lot. “Oh my God, we’ve got to wash our hands and sanitize our surgical equipment and get a flu shot and do this and do that.” But now, we don’t even think about it. We just do it every day as part of the regular course of the world because that’s how our society was built. 

And similarly, if you think about it in terms of “Dr. Burke Harris is telling me I need to exercise, and then I need to work on my sleep hygiene, and then I need to do this and that and the other,” it feels really overwhelming. But instead, just recognize it as an approach and then just do a little check and say, “How’s my stress response doing? Do I notice that it’s a little overactive? Let me take time to figure out my ACE score,” and go from there. Then begin to notice which situations dial my stress response up or down. “Is my relationship supporting stress relief? Or do I notice that when my partner comes home my heart starts to pound when his keys are jangling in the door?” It’s using this knowledge as a compass and then taking it from there, rather than seeing it as this really daunting, huge to-do list.

Greg: You mentioned the ACE score. What is that and how would someone measure it or calculate it?

Nadine: There’s a website called, which is a website that was launched by our organization to help families and parents and individuals learn more about toxic stress. You go to that website and you can take the ACE test right there.

Greg: Would there be multiple practitioners involved in a treatment protocol for ACEs?

Nadine: Absolutely. One of the biggest ways we’re going to address this issue is doing early detection. The research shows that when we do early intervention, folks have much better outcomes. Now it’s never too late to be doing this work, but the earlier we start, the more tools we have and the better off we are. Then once we do this early identification, it’s a multidisciplinary response. For some reason, we have this kind of artificial separation in our culture between what’s above the neck and what’s below the neck. And that’s not really how it works. The body doesn’t make that distinction. So oftentimes it does take a multidisciplinary team to address the issues. That’s what we do at our center and that’s what I really recommend as the best practice.

Greg: So at your center, you have multiple practitioners who are working toward the same treatment goal but have slightly different clinical focuses?

Nadine: Right. What’s critical about that is not just that they’re working towards the same goal but that they also have the same framework. Because oftentimes, you have the doctor working on the health problem, you have the therapist working on the mental health symptoms, but they haven’t come together to say, “Oh, the fundamental problem is an overactive stress response.” So doctors need to be targeting that, mental health practitioners need to be targeting that, we have a nutritionist who’s really focused on that—everyone on our team is focused that the fundamental problem is an overactive stress response.

Greg: Well, that’s all the questions I have. Is there anything else you want to add?

Nadine: I’m on a mission to get every pediatrician in America to be screening for childhood adversity because I think that is the key to prevention. Unfortunately, right now only four percent of pediatricians are doing it. But I hope that in ten years it’ll be a different story. And it’s really important for everyone to be part of the solution, whether it’s doing your own pulse-check and figuring out whether this is an issue for you, but also figuring out how you can advocate in your community or your environment.

Greg: Thank you very much, and congratulations on the new book.

Nadine: Thank you. And thank you for taking the time.

The Deepest Well: Healing the Long-Term Effects of Childhood Adversity is available on Amazon. For more insights from Nadine Burke Harris, follow her on Facebook and Twitter. Learn more about the Center for Youth Wellness by connecting on the web, Facebook and Twitter. And enter the giveaway below to win a hardcover copy of The Deepest Well.

For more interviews like this one, check out The KineSophy Library.