A toddler came into my examination room recently at Bayview Child Health Center in Bayview Hunters Point, an underserved, largely African-American neighborhood in San Francisco. Her mother was worried that she wasn’t growing properly, and she was right: At the age of 2½, her daughter ranked at the very bottom of the height and weight charts that pediatricians use to gauge whether kids are growing normally. My patient’s mom had tried everything she could to help her daughter eat right and gain weight but nothing seemed to be working. It appeared to be a classic case of what doctors call “failure to thrive."

Lots of children “fail to thrive,” for one reason or another, with higher rates occurring in economically disadvantaged areas. Decades of research have linked race and income to health disparities: If you are poor and African-American or Latino, the statistics show that you are more likely to have asthma or obesity as a child, and get a heart attack or die of cancer as an adult.

But the statistics alone can’t tell you why. My patients taught me the answer. It turns out that there’s a little-known factor damaging long-term health that plays out most profoundly in struggling communities like Bayview yet can affect Americans of any ethnicity, background or income level: toxic stress in childhood. As the United States grows more diverse, understanding the science behind toxic stress gives us new tools to improve the health of ethnic minorities and those from disadvantaged backgrounds.

The seminal research that uncovered the link between childhood stress and adult disease had nothing to do with race or poverty. It was a survey of over 17,000 mostly white, college-educated Californians published by the Centers for Disease Control and Prevention and Kaiser Permanente in 1998. The researchers asked respondents about their childhoods and counted up how many “adverse” experiences they had. Did your parents divorce? Did a parent drink too much, take drugs or have a mental illness? Did a caretaker ever hit you or fail to take care of you? Was anyone in your household sent to jail?

The results were astonishing: Nearly two-thirds of the San Diego patients had at least one adverse experience, and 1 in 8 had four or more. More important, there was a strong and direct correlation between the number of adverse childhood experiences and poor health in adulthood — the higher the number of adverse childhood experiences, or ACEs, the higher the risk of disease. People who had four or more ACEs were twice as likely to have heart disease, twice as likely to have cancer, and almost four times as likely to suffer from emphysema or chronic bronchitis. Later research showed that people with six or more ACEs died nearly 20 years earlier than did those with none.

Importantly, research has shown that the number of ACEs has a much stronger association with long-term health outcomes than race or income.

Despite this powerful data, medical practice does too little to recognize and address the impacts of toxic stress. At my clinic in Bayview, we have developed a simple way to screen for ACEs and we’re piloting the best ways to counteract them. Patients or parents fill out a questionnaire that calculates a total ACE score, without making the patient say exactly what kinds of adversity they have experienced, and the score is included in their records. As a result, we can screen every child for toxic stress as part of their routine physical exam.

Children who grow up in disadvantaged neighborhoods, like these boys in East Chicago, often experience toxic levels of stress in their childhoods that set them up for a life of poor health. | Getty

For the little girl who was failing to thrive, I could see that she had been exposed to a particularly large number of ACEs — in her case, seven. When I told her mom that her daughter’s problem gaining weight might not be a food problem but a stress problem, it was like a light bulb turned on in her head and she saw her daughter’s situation differently. She remarked that her husband had spent time in rehab, and that when he was away her daughter seemed to pick up weight, but when he returned it seemed her daughter would go backward. “I noticed the change’’ mom told me, “but I didn’t realize it could be related.’’

I can’t tell you the relief that so many of my patients express when they understand that their experiences might be affecting their biology. This is particularly true for my teenagers. I tell them, “Because of what has happened to you, your body tends to make more stress hormones than the average person. Sometimes that can look and feel like having a tough time controlling your impulses, being quick to anger or getting sick easily when you are overwhelmed. Does any of that feel familiar to you?” The response I hear most often is, “You mean I’m not crazy?”

Children’s brains and bodies are particularly vulnerable to toxic stress. Because of the brain’s high level of plasticity in early childhood, negative experiences can deeply impact brain development. High levels of stress hormones can lead to changes including loss of brain cells, damage to cell connections, enlargement or shrinking of certain parts of the brain. For this reason, behavior is often the canary in the coal mine: Kids come to my attention with symptoms of poor impulse control or learning and developmental problems. (For kids without behavioral symptoms, the signs are less often recognized.) Chronic stress can also lead to changes in hormonal levels, inflammation in the body and premature cellular aging which can contribute to heart and pulmonary disease including asthma, as well as diabetes and cancer.

However, we now know that the same plasticity that makes children vulnerable to adversity also makes them most responsive to positive countermeasures. New understanding of the biology of toxic stress allows us to target the pathways that are disrupted with greater insights than we ever had before. Treatment involves reducing the child’s dose of adversity and strengthening the ability of their caregiver to be a protective buffer against their child’s stress. More sleep, better nutrition, exercise and mindfulness techniques like meditation are also helpful — they reduce stress hormones and inflammation, increase neuroplasticity and delay cellular aging. But we still have a lot of work to do to understand how to deploy these tools in the right combinations to produce the greatest effect.

Advances in our understanding of toxic stress represent a tremendous opportunity for our entire society. While we know that racial discrimination contributes to the adversity experienced by some communities, national data reveal that adverse childhood experiences are far from a black and brown problem. Some of the U.S. states with the highest ACE scores are disproportionately white and rural — for instance, Oklahoma, Kentucky and Montana all rank near the top for the proportion of the population of children with two or more ACEs. In my home state of California, the county with the highest prevalence of ACEs is 83 percent white. It’s not a coincidence that communities struggling with high opioid use are also communities where residents have endured toxic stress. And like Bayview Hunters Point, those communities are under-resourced, which means they are less able to provide the kind of interventions that can counteract the damage.

This isn’t just a problem for the individuals affected; our nation is paying a profound economic cost for toxic stress. Having an ACE score of 4 or more is associated with elevated relative risk of developing 7 of the 10 leading causes of death in the U.S. And if we pursue policies that aggravate adversity in our communities, instead of investing in programs that support all children and families, we will continue to pay for it downstream. We’ll pay for it in health care costs. We’ll pay for it in lost productivity. We’ll pay for it in reduced competitiveness.

When the little girl came back for a follow-up visit, her mother told me that dad was no longer in the home. She was beginning to understand how to better shield her daughter from experiences that might be damaging. And the little girl had gained 2 pounds in two months — a big improvement in a short amount of time.

Understanding the science of ACEs and toxic stress gives us a powerful tool for not only addressing health disparities, but for improving the lives of all Americans. When we wake up to the fact that my patient in Bayview shares a common biology with every child in America who is experiencing adversity, then perhaps we can find the will and the resources to help all children thrive.

Nadine Burke Harris is a pediatrician and founder of the Center for Youth Wellness, a San Francisco based nonprofit.

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