W. Thomas Boyce, MD, is chief of the division of developmental medicine at the University of California, San Francisco, School of Medicine. He researches the effect of poverty, social subordination, and stress in early childhood on the risk of subsequent physical and mental disorders.
You refer to the “biology of misfortune.” What is that?
There’s a lot of new research into the development origins of health and disease in adulthood. And we’re finding that pervasive, grinding, chronic adversity in childhood—what some call toxic stress—leads to physiological changes in children and an increased risk of chronic disease and early death in adulthood.
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What types of adversity constitute toxic stress?
There are adverse childhood experiences like divorce or abuse. Then there are longer-term adversities such as living in poverty, neglect, or being bullied perennially at school or at home. They’re not really events, they’re just the way life is, unfortunately, for a growing number of kids. There’s evidence that children who are growing up in adverse circumstances have higher incidences of asthma, heart disease, obesity, type 2 diabetes, and psychiatric disorders that carry on into adult life. There have been studies that control for diet and exercise, and just being in a lower social class affects health in the longer run, independent of other risk factors.
How could childhood stress lead to something like heart disease later in life?
We have two principal stress response systems in the brain. One is the locus coeruleus, a tiny nucleus in the brain stem that ignites our fight or flight reflex. It can cause sweaty palms, dilated pupils, and other signs of stress in times of severe adversity. The other is the corticotrophin-releasing hormone (CRH) system, a chemical signal produced by the hypothalamus in our brains. It drives the secretion of the stress hormone cortisol.
Elevated levels of cortisol alter the function the immune system. That’s good if you’re facing an immediate threat to safety or survival and need a well-prepared immune system. But it’s bad if there’s no immediate outside threat. Kids growing up in more chronic, high stress, and impoverished circumstances show a shift toward inflammatory responses in their immune system. And we know that inflammation is related to many chronic diseases, including asthma, heart disease, and hypertension.
From a public health perspective, why does this matter?
One reason it matters is that there are long-term consequences: chronic disease, and poorer physical and mental health. This affects our health system and our economy. Jim Heckman, the Nobel Laureate economist, estimates that for every dollar we spend on prevention in early childhood, society gets back 17-fold over the lifetime of that individual. So, if there were things we could do to change exposures to toxic stress in kids, every dollar spent would have a $17 return on investment in the longer term.
Another reason is that this problem actually shortens the life of too many people. Ongoing, chronic stress exposures not only magnify the incidence and severity of physical and mental disorders, but also accelerate aging and mortality.
A third reason is that we claim to be an enlightened, egalitarian democracy that prides itself in providing equal opportunities to all its people. We don’t have that in this country today. If we want to provide generations of children an equal chance to succeed and thrive, we have to do something about their early lives.
What are possible solutions?
One partial answer is that you provide earlier and more cognitively stimulating kinds of environments. The Carolina Abecedarian Project is one example of that sort of intervention. Forty years ago, they identified a cohort of kids in rural North Carolina, then randomized them into intervention and control groups. The intervention kids got exposure to books and reading, strong daily routines, and socioemotional support very early in preschool. Researchers initially examined IQ as a measure of program effects, and found that the benefits were substantial but temporary—that is, the intervention increased kids’ IQs compared to the control group, but the differences disappeared over time.
But it turns out that—35 years later—adults who had been given this early childhood intervention had lower rates of metabolic syndromeand lower levels of diabetes and hypertension. They were in better physical health.They were also more likely to have a college degree and a job than other kids in the study.
But if we are going to invest seriously in the lives of children, we need to begin planning even earlier interventions that provide more than simply cognitive stimulation. We need to start considering how we can foster better parenting. It’s really parenting that has the most intense effect on the socioemotional development of kids. In the longer term, creating better parents is going to have far more positive effects on kids than that first generation of preschool cognitive stimulation programs.
More than a quarter of kids in America live with a single parent, which increases the odds of growing up in and continuing into poverty. We need to think about ways to keep both parents in the household, and we need to consider ways to render this a more equal and fair society. We know that, worldwide, more unequal societies have less attentive and positive parenting than more equal societies. Where there are greater differences in income, there are also greater differences in parenting. One of the answers to the problem of chronic disease has to be a commitment to a more equal and just society.
This opinion does not necessarily reflect the views of the UC Berkeley School of Public Health or of the Editorial Board of BerkeleyWellness.com.