How do our biological systems work together to respond to chronic stress? What do these responses mean for early learning and lifelong health? And when we say that early experiences matter, what do we mean by early? This episode of The Brain Architects podcast addresses all these questions and more!
To kick off this episode, Center Director Dr. Jack Shonkoff describes the body’s stress response system, how our biological systems act as a team when responding to chronic stress, and the effects chronic stress can have on lifelong health.
This is followed by a discussion among a panel of scientists including Dr. Nicki Bush (University of California-San Francisco), Dr. Damien Fair (University of Minnesota), and Dr. Fernando Martinez (University of Arizona). The panelists discuss how our bodies respond to adversity, inflammation’s role in the stress response system, the effects of stress during the prenatal period and first few years after birth, and how we can use this science to prevent long-term impacts on our health.
Sally: Welcome to The Brain Architects, a podcast from the Center on the Developing Child at Harvard University. I’m your host Sally Pfitzer. Our center believes that advances in science can provide a powerful source of new ideas that can improve outcomes for children and families. We want to help you apply the science of early childhood development to your everyday interactions with children and take what you’re hearing from our experts and panels and apply it to your everyday work.
In today’s episode, we’ll discuss how early experiences, especially during the prenatal period and first few years after a baby is born, get inside the body and can have long–term impacts on lifelong health. Here to help us dig into that science around the early years and lifelong health is Dr. Jack Shonkoff who is the Professor of Child Health and Development, and the Director of the Center on the Developing Child at Harvard University. Hi Jack. It’s really great to have you back.
Jack: Hi Sally. Great to be with you. Thanks very much.
Sally: Let’s dive right in. In previous podcasts, we’ve discussed the impacts of stress and specifically you referred to this term of toxic stress, but we never really went too much into the detail about the body’s stress response system. I’m wondering if you could explain how the body responds to stressors or adverse experiences and environments.
Jack: Yeah. That’s a really good question. For starters, the fact that we have a stress response system is really good. It’s protective for us. It actually can be lifesaving. It’s built into our body because this is how we deal with threat or challenges or hardships. This is the basis of the fight or flight response. So, what’s going on inside our body? Well, when we are stressed, a number of systems in the body get activated. Stress hormone levels are elevated and distributed all through the body. Our heart rate goes up, our blood pressure goes up. This is controlled by signals from the brain to the heart and the cardiovascular system. Our immune system is activated and there’s an inflammatory response. Our metabolic systems are activated to produce more energy for our body—more energy for our muscles, if we have to run or if we have to fight or more energy to think more clearly.
The important message here is that the stress response is not just in our brain, it’s in all of the biological systems in our body that are constantly communicating with each other. They’re all reading the environment, they’re getting feedback, they’re communicating with each other. And this is what allows us to deal with challenges, to deal with an acute threat. The best way to think about this is to think about your brain and your immune system and your metabolic system and your cardiovascular system as all different members of a team. Success as a team depends upon each member of the team having a specific contribution to make. And a successful team depends upon interaction and alignment with each other. If any one part is not pulling its own weight, that affects the whole team.
The immune system is another one of those team players. It is our body’s defense against infection. It’s our body’s ability to respond to injuries that require wound repair, and also helps us to be protected against other kinds of toxic exposures that might come in. Inflammation is the first response of the immune system to the threat of let’s say infection, or let’s say a wound like a cut. Think of it as the mobilization of the kind of first responders of our biological system. Now, everybody knows what inflammation looks like outside the body. When you have a cut or some kind of an injury that’s bleeding, and as it starts to heal, you notice that the area around the cut is red, it can be warm in the beginning, it may be particularly sensitive or painful. That’s the inflammatory response that is actually fighting against germs coming in. It’s kind of cleaning out body tissue that may have been injured by bacteria or viruses or trauma, physical trauma and it is beginning to initiate the healing process. And then over time the redness goes away and it’s less painful and the wound is healed.
Well, that inflammation also can happen internally in the body. Now, in the beginning in a stressful situation, inflammation is very helpful internally. It mobilizes your body’s defenses against infection, and it’s meant to then deal with that acute injury or threat and suppress it. But what happens if the stress continues? This is what we refer to as toxic stress. So, in the beginning, it’s protective, but over time, that inflammation can then start to have a wear and tear effect on the body. It can actually start to disrupt organ systems. Here’s one or two examples. We know that inflammation accelerates atherosclerosis, kind of forming plaques that can clog up your arteries around your heart. Inflammation can also affect metabolic systems leading to insulin resistance internally and increasing the risk for diabetes. Individuals who have severe depression have elevated inflammatory markers in their body, evidence of elevated inflammation.
We know that chronic inflammation internally doesn’t automatically mean you’ll get any of the diseases that I just mentioned, but it means that it increases your risk, which is now beginning to help us understand what is it about chronic severe stress that makes people more likely to develop chronic diseases, not just mental health problems, but physical health problems.
Sally: That’s really interesting. And hearing you talk about how early experiences of chronic stress can have more of a long–term impact, I’m imagining that these impacts are not likely evenly distributed. Right? And I’m wondering if you can talk a little bit more about that.
Jack: We have a very serious problem certainly in this country of unequal access to healthcare and unequal treatment in the health care system. And those are very important and clearly need a lot of work. But that’s not the whole story about disparities in health outcomes. Before we get to issues about healthcare, how does it happen that we have inequalities in the prevalence of many stress-related diseases like heart disease and hypertension and stroke? The new science is helping us get inside the body and say what is it about chronic stress and chronic hardship that leads to health problems? How does that happen? Some of this we’ve talked about already, which is the chronic activation of multiple parts of the stress response system that can have a wear and tear effect on different organs and biological systems leading to the most common and the most expensive chronic diseases in adult life.
So, when we think about that problem of chronic adversity, and we know there are some very consistent and predictable differences in terms of racial and ethnic disparities in health outcomes, starting with prematurity and low birth weight, and then extending all the way up to obesity and heart disease and type 2 diabetes and a variety of other chronic disorders. So how do we understand this? Well, here is some of the things that are very important for all of us to focus on. Number one, the differences by race and ethnicity are not genetic. There may be for some individuals, a greater risk for some diseases related to genetics, but from a population basis, certainly for race, race is a social construct, there’s no biological basis for race and certainly not when we’re talking about illnesses.
This gets us back to the discussion that we’ve been having about how chronic stress and chronic stress activation lays the foundation for greater risk for health problems later in life. Often, we make a list of sources of chronic adversity. We talk about poverty, we talk about racism, we talk about exposure to violence, we talk about a serious mental illness in a family, a young child living alone with a mother with severe depression who loves her child as much as any mother does but can’t be consistently responsive because of depression which is an illness. The body’s stress system and its response is the same regardless of the source of the stress.
There’s something about systemic racism and the kind of interpersonal discrimination that’s part of the daily lives of people who are subjected to structural inequities, things that are built into society, that really requires us to take a careful look and say on the one hand, racism is a source of stress like many other sources of stress, but on the other hand, systemic racism and being constantly subjected to the indignities of discrimination raises a different question, which is: what do we do about that? How do we protect young children from the racism that their families and other caregivers have to deal with?
The real solution to this is to go upstream and to deal at the source with the hardships and the threats of systemic racism that are bearing down on families, rather than focusing on helping families to cope with that racism. This is prevention in its true sense, which is not just to kind of put a band–aid on things, but to go to the source. I think the increased consciousness that we have in our society right now about systemic racism in a way that has always been known to families of color, but has sometimes been invisible—many times been invisible to families who do not know what it’s like to be victimized by chronic racism presents a really important opportunity for us to be much smarter and much more effective about how we think about this issue.
Sally: You brought up some really important points. And we’re actually going to be getting more into the policy and system solutions in the next episode, so stay tuned. But can you tell us a little bit more about why early in childhood development is so important? So, I know we say early a lot, but what does that actually mean?
Jack: Yeah. This is a really important question about what we mean by early and this is one of the real game changers about connecting the brain to the rest of the body. There’s an increasing public understanding that chronic stress activation can affect the development of the brain and ultimately affect your readiness to come to school prepared to succeed. But what this new science is telling us as we connect the brain to the rest of the body, is it’s not just about early learning, it’s also about the foundations of lifelong health.
And if you think about the way we approach early childhood policies and early childhood programs, we have over the years realized that kindergarten is a nice time to start school, but actually it’d be better to start school earlier especially for children who are living under difficult circumstances. We have been increasing our investment in preschool for three and four-year-olds. Makes a lot of sense, good decision in terms of public policy. But for the children who are experiencing the most severe stress, that’s not early because the effects of this serious adversity begin very early.
In fact, they begin even before you’re born. A pregnant woman who is in an environment where there’s very little support, where there’s constant stress activation, and also may