Message from the Director

The role of toxic stress in health outcomes

Dr. ThornburgSummer 2018

While the work of the Moore Institute has traditionally focused more on the role nutrition plays in lifelong chronic disease risk, toxic stress plays an equally important role and often goes hand in hand with poor nutritional access. In fact, it is often difficult to tease apart the role each plays because they are so closely entwined.

Toxic stress, also referred to as chronic stress, is frequent or prolonged exposure to adversity. This can take the form of abuse, neglect, exposure to violence, or extreme economic hardship. Children born to mothers experiencing toxic stress are often born into an environment that doesn't promote health, with less access to nutritious foods, stable housing, health care access and the like. We know that people of color experience disproportionate rates of toxic stress and can trace the impact that has on their lifelong health and that of their children.

The news this summer about families being separated as they cross the U.S. border and the protests at the ICE offices just down the road from us paints a vivid picture of this. The situations these families must be leaving to attempt the desperate crossing into the U.S. where they risk being unable to find employment, housing, health care, and ultimately being discovered and sent back is unimaginable. No matter your stance on individuals who cross into this country without following established legal protocol, one thing is clear, the trauma suffered by these children will last a lifetime and will help continue the cycle of poor health and chronic disease risk for years to come.

Children born to mothers who experienced toxic stress are more likely to be born prematurely and with a low birthweight. They are also substantially more likely to have social, emotional and cognitive problems as they develop. These often take the form of behavior problems, attention deficit/hyperactivity disorder and poor language development, all of which impact school readiness and academic performance.

We're still learning the exact mechanisms by which toxic stress harms a developing child. One likely pathway is through increased stress hormones. Any type of social stress causes a number of "fight or flight" hormones to be released directly into the blood stream. In the short-term these hormones help a person cope in response to a perceived threat. Cortisol is one of these hormones. Cortisol levels in the blood are normally highest in the morning and decrease throughout the day. However, when a person experiences toxic stress it's like the body's alarm button is stuck in the "on" position and cortisol levels remain elevated throughout the day.

Maternal levels of cortisol increase gradually during pregnancy and it doesn't affect the developing baby because it is "neutralized" by an enzyme released by the placenta. However, under conditions of toxic stress in the mother, the high levels of cortisol in maternal blood overwhelm this enzyme and cortisol enters the fetus and leads to harmful effects like organ growth suppression. This in turn leads to low birthweight babies.

The problems don't stop after birth. In children, toxic stress can cause permanent changes to the structure and function of the brain, resulting in increased risk of mental health disorders and chronic disease later in life. And women born to mothers who experienced toxic stress are more likely to experience it themselves as adults and in turn give birth to small babies. In this way, the cycle of chronic disease is perpetuated.

This cycle has become ever more apparent to us as we have developed relationships with communities and groups across the state working to improve health among Oregonians of color. In particular our work in rural areas of Oregon and with groups like Familias en Acción have shown us how intertwined the issues of healthy eating, poverty, employment and racism really are. Some communities cannot begin to discuss healthy food access and consumption without first addressing issues like affordable housing and underemployment.

We know the road ahead of us is daunting in making a real impact on the prevalence of chronic disease among Oregonians and the disproportionate rates many of our communities face. However, we believe that by working together we can change the future for the better. We must continue to find ways of working together to build strong foundations for lifelong health for everyone.


Kent L. Thornburg, Ph.D.
Director, OHSU Moore Institute for Nutrition & Wellness