美国国家公共电台 NPR Nadine Burke Harris: How Does Trauma Affect A Child's DNA?（在线收听）

GUY RAZ, HOST:

So if Moshe Szyf is right, that positive experiences can rewrite DNA and improve health, what about negative experiences? Well, about 10 years ago, a pediatrician named Nadine Burke Harris was asking herself that very same question.

NADINE BURKE HARRIS: In the back of my mind, I always thought, like, I wonder if stress hormones are affecting the health of my patients. I'm like, I wonder if that's even possible.

RAZ: Back then, Nadine had just finished her medical training at Stanford.

BURKE HARRIS: That's right. I started a clinic, a pediatric clinic, in Bayview-Hunters Point, which is one of San Francisco's most low-income and underserved neighborhoods.

RAZ: And as soon as Nadine opened that clinic, she started to notice something.

BURKE HARRIS: A lot of kids were being referred to me by teachers, by principals, by school counselors for ADHD. It was a lot. Like, it wasn't (laughter) - it wasn't, like, two or three. It was a lot.

RAZ: And then she noticed another thing that, at first, seemed totally unrelated. One of her patients came in with asthma.

BURKE HARRIS: I asked, what could it be that could be setting off, you know, your daughter's asthma? Could it be, you know, pet dander or could it be pollen? Like, when do you notice that her asthma flares up? And this mom said to me, you know, doctora, I noticed that her asthma tends to get worse when her dad punches a hole in the wall.

RAZ: And hearing that convinced Nadine to start asking all of her patients about what was happening at home.

BURKE HARRIS: So I had all of these patients who had these symptoms of ADHD, asthma, eczema, you know, skin rashes - right? - but who also had severe histories of adversity, you know, violence in the community, violence at home, parents who are either mentally ill or substance dependent or incarcerated. What I observed, and I started to notice this pattern, was that my patients who had the worst symptoms were also the ones who had the worst histories of adversity.

RAZ: So you start to think that this adversity, this trauma is potentially affecting their physical health.

BURKE HARRIS: Yes.

RAZ: But this was a hunch at the beginning, right?

BURKE HARRIS: Yes, that's exactly right. Yeah, it's like that voice in the back of your mind saying, ha.

RAZ: So what did you do?

BURKE HARRIS: Well, one day, my colleague Dr. Whitney Clarke walked into my office and he said, have you seen this? And he was holding in his hand a research paper called the Adverse Childhood Experiences Study. And it was like I was hit by a bolt of lightning.

RAZ: Yeah.

BURKE HARRIS: Because what it said was childhood adversity in and of itself is a risk factor for major health problems.

RAZ: The study seemed to confirm what Nadine had suspected all along, that adversity could rewire a child's brain and body, Nadine Burke Harris picks up the story from the TED stage.

(SOUNDBITE OF TED TALK)

BURKE HARRIS: That day changed my clinical practice and ultimately my career. The Adverse Childhood Experiences Study was done by Dr. Vince Felitti at Kaiser and Dr. Bob Anda at the CDC. And together, they asked 17,500 adults about their history of exposure to what they called adverse childhood experiences or ACEs. Those include physical, emotional or sexual abuse, physical or emotional neglect, parental mental illness, substance dependence, incarceration, parental separation or divorce or domestic violence. For every yes, you would get a point on your ACE score.

And then what they did was they correlated these ACE scores against health outcomes. What they found was striking. Two things - number one, ACEs are incredibly common. Sixty-seven percent of the population had at least one ACE and 12.6 percent, 1 in 8, had four or more ACEs. The second thing that they found was that there was a dose response relationship between ACEs and health outcomes. The higher your ACE score, the worse your health outcomes.

For a person with an ACE score of four or more, their relative risk of chronic obstructive pulmonary disease was 2.5 times that of someone with an ACE score of zero. For hepatitis, it was also 2.5 times. For depression, it was 4.5 times. For suicidality, it was 12 times. A person with an ACE score of seven or more had triple the lifetime risk of lung cancer. And 3.5 times the risk of ischemic heart disease, the number-one killer in the United States of America. Some people looked at this data and they said, come on, you know, you have a rough childhood, you're more likely to drink and smoke and do all these things that are going to ruin your health.

This isn't science. This is just bad behavior. It turns out this is exactly where the science comes in.

RAZ: In just a moment, Nadine Burke Harris explains how childhood adversity can rewrite a child's DNA. Stay with us. I'm Guy Raz, and you're listening to the TED Radio Hour from NPR.

(SOUNDBITE OF MUSIC)

RAZ: It's the TED Radio Hour from NPR. I'm Guy Raz. And on the show today, Hardwired - ideas about how our biology and our experiences determine who we are. And before the break, Pediatrician Nadine Burke Harris was explaining that childhood adversity is one kind of experience that can result in severe health problems.

(SOUNDBITE OF TED TALK)

BURKE HARRIS: We now understand better than we ever have before how exposure to early adversity affects the developing brains and bodies of children. It affects areas like the nucleus accumbens, the pleasure and reward center of the brain that is implicated in substance dependence. It inhibits the prefrontal cortex, which is necessary for impulse control, an executive function, a critical area for learning. And on MRI scans, we see measurable differences in the amygdala, the brain's fear response center.

So there are real neurologic reasons why folks are exposed to high doses of adversity are more likely to engage in high-risk behavior. And that's important to know. But it turns out that even if you don't engage in any high-risk behavior, you're still more likely to develop heart disease or cancer. The reason for this has to do with the hypothalamic-pituitary-adrenal axis, the brain's and body's stress response system that governs our fight-or-flight response. How does it work?

Well, imagine you're walking in the forest, and you see a bear. Immediately, your hypothalamus sends a signal to your pituitary, which sends a signal to your adrenal gland that says, release stress hormones adrenaline, cortisol. And so your heart starts to pound. Your pupils dilate. Your airways open up. And you are ready to either fight that bear or run from the bear. And that is wonderful if you're in a forest, and there's a bear. But the problem is what happens when the bear comes home every night. And this system is activated over and over and over again.

And it goes from being adaptive or lifesaving to maladaptive or health-damaging. Children are especially sensitive to this repeated stress activation because their brains and bodies are just developing. High doses of adversity not only affect brain structure and function. They affect the developing immune system, developing hormonal systems and even the way our DNA is read and transcribed.

RAZ: Wow. So, I mean, that child then exhibits certain behaviors based on that exposure, I guess, right?

BURKE HARRIS: That's exactly right. Probably, I would say behavior is the canary in the coal mine. So some kids demonstrate behavioral symptoms and as adults - more likely to suffer from depression, attempt suicide, have problems in the workplace, become incarcerated. But some kids don't show any behavioral symptoms. Some kids just get sick all the time - rashes or asthma or auto-immune disease - right? - where your immune system attacks your own body, right? And then they're more likely to be sick adults - heart disease and arthritis and cancer and strokes and chronic obstructive pulmonary disease and Alzheimer's.

RAZ: I mean, the kids that you have seen, right? - is there any hope? I mean, is it reversible? Is there any way to deal with that?

BURKE HARRIS: Yeah. So the good news is, yes, now that we know that your environment has such a profound effect on your biology. One of the most important things that we can do is early detection.

(SOUNDBITE OF TED TALK)

BURKE HARRIS: So in San Francisco, we created the Center for Youth Wellness to prevent, screen and heal the impacts of ACEs and toxic stress. We started simply with routine screening of every one of our kids at their regular physical. For our patients who do screen positive, we have a multi-disciplinary treatment team that works to reduce the dose of adversity and treat symptoms using best practices, including home visits, care coordination, mental health care, nutrition, holistic interventions and, yes, medication when necessary. But we also educate parents about the impact of ACEs and toxic stress the same way you would for covering electrical outlets or lead poisoning.

RAZ: I mean, this is incredible because what you're saying is with the right intervention, you can prevent and even sometimes reverse these huge health problems.

BURKE HARRIS: Yeah. And here's what's awesome - is that we're seeing that it works. I literally last week had a follow-up appointment with a patient who is a young girl who had experienced 7 out of the 10 adverse childhood experiences. And this child had stopped growing. She had a diagnosis of failure to thrive. And we implemented some of the things we know to be best practices. We did an intervention called child-parent psychotherapy. But a big part of it was just educating mom about how the child's exposure to adversity was affecting her health. And I will tell you she's back on the growth curve. This family's doing amazing. We can reverse the effects of stress hormones if we detect it early enough. And those things will change their biology.

RAZ: Nadine Burke Harris is a pediatrician and the founder and CEO of the Center for Youth Wellness in San Francisco. You can see her full talk at ted.com.