INSTITUTE FOR POLICY RESEARCH

As a graduate student at the University of California, Los Angeles, IPR health psychologist Greg Miller found himself at “ground zero” of a new field investigating how the mind, body, stress, and health all connect.

“There was a lot of excitement,” Miller said. “People thought they were on to something new and they were.”

Many studies have noted how a child born into economic hardship has a higher risk of heart disease, disability, and even premature mortality than a child born to a higher-class family. This new field, though, went beyond pinpointing lack of resources as the cause of these disparities.

“It’s fairly easy to come up with explanations for why people who are really short in resources have worse health compared to people who are very affluent,” Miller said. “But at a certain point on the resource distribution, people have plenty of food and they have all their basic needs met. Yet, above that, there’s still this socioeconomic gradient in health.” 

He explained that all along the gradient, psychological influences matter—they just might be different depending on where someone stands on this spectrum. 

Miller studies these psychological influences, focusing on how early childhood stressors can lead to disease later in life. He began this research as a graduate student—when he also met his wife and frequent research partner, IPR health psychologist Edith Chen.

“People at Northwestern tend to think of us as a unit,” Miller said, although they did not start working together until about 10 years ago. The two do about 50 percent of their research together, and they are co-directors of the Foundations of Health Research Center, which examines the relationship between socioeconomic status (SES) and health across the lifespan. 

"I really like being at those kinds of intersections where the goal is to integrate knowledge from really distinct spheres and think about how it connects, which is why IPR is such a perfect fit for me,” Miller said. 

Stress and health during pregnancy

The link between SES and health begins early and seems to be transmitted across generations: Working with IPR anthropologist Thomas McDade and IPR associate Ann Borders, a professor of obstetrics and gynecology, Miller has shown that women who were economically disadvantaged in childhood have more adverse birth outcomes when they begin families of their own.

Using data from the Measurement of Maternal Stress study, which Borders led, the researchers find these women's children are more likely to be born prematurely and have a low birth weight. These babies are almost 50 percent more likely to be admitted to the Special Care Nursery, and they spend an average of almost five additional days in the hospital.

The findings suggest that “it’s not just what happens in pregnancy that affects how that pregnancy ends, but also what happens before the pregnancy,” Miller said. 

Childhood origins of cardiovascular risk

Socioeconomic status early in life can affect health years later—such as by raising the risk of coronary heart disease (CHD). But what leads to this increased risk?

Miller has found that low SES in childhood is linked to increased abdominal fat and inflammation in adulthood. He has also discovered this inflammation increases vulnerability to chronic diseases like CHD.

Through the My World, My Heart study, Miller and his lab are seeking to understand the pathways that lead to these socioeconomic disparities in heart disease risk. They are studying a sample of Chicago-area youth who are in eighth grade, and will follow them up again in tenth grade, to observe health changes across the transition to high school. The focus of the study is how socioeconomic status relates to children’s brain and immune development, and what implications that has for behavioral and biological processes that increase the risk of CHD.

“We know that the process of cardiovascular risk starts in the early years of life, and kids from more and less advantaged backgrounds diverge in adolescence in terms of their mental and physical health,” Miller said. “This study adds a fine-grained look at when and how they diverge, and whether the differences in heart attack or stroke risks in later life are due to processes that start at 12 or 14.”

The cost of resilience

Though they face additional obstacles in doing so, some low-income children beat the odds by performing well in school and going on to college. These children are considered resilient, because they achieve positive outcomes in adverse circumstances. Miller began studying resilient youth several years ago, hypothesizing that they might avoid some of the health problems common in low-income youth. 

However, the opposite turned out to be true. In a study of 489 rural African-American youth in Georgia, who were tracked from ages 11 to 19, Miller and his colleagues discovered the resilient young people were more obese, had higher blood pressure, and produced more stress hormones than their peers.

Miller has expanded this line of work, finding in a 2015 study that a group of low-income youth appeared to be resilient, based on lower rates of depression and substance abuse. But these youth also showed faster epigenetic aging—their cells looked “older” than they actually are chronologically, and research suggests these older cells are related to health problems later on.

Miller and his colleagues are considering ways to mitigate these health effects. With Chen and IPR social psychologist Mesmin Destin, Miller is piloting an intervention study that seeks to help lower-income, higher-achieving young people balance their school and health goals, and “blow off steam” in productive ways.

“Our country has many strong points but many big social problems,” Miller said. “I like to think that the research we do helps identify some of the roots of those problems and points to potential solutions.”

Greg Miller is professor of psychology and an IPR fellow.