How young children manage stress

Looking for links between temperament and experience

Stress—the emotional and physical impact our bodies experience as we adjust to challenge—is a normal part of life. Whether caused by daily demands or a physical threat, stress triggers a primal physical response, releasing hormones that ready the body to react, then return to normal. Yet today many people suffer from chronic stress, which is linked to heart disease, depression, diabetes, and countless other health problems leading to early death.

Scientists believe our ability to manage stress as adults is formed in childhood through a combination of genes and experiences. For two decades, Megan Gunnar, child development professor and director of the Human Developmental Psychobiology Lab, has pioneered the field of measuring stress in young children as a way to unravel the mysteries of healthy development.

“Some individuals experience stress from minor problems, while others let everything roll off their backs,” says Gunnar. “Our research seeks to understand how this range of differences develops and impacts our mental and physical health.”

How the research is conducted

Gunnar’s lab assesses children’s stress levels by measuring cortisol, a blood-borne hormone that increases under stress. This hormone leaks into and can be measured in saliva. To make saliva collection enjoyable, Gunnar and her students have developed a playful testing method called the “Tasting Game,” where children suck on test strips they first get to dip in a sweet substance that increases saliva flow.

What the research shows

Gunnar’s research finds that social relationships control cortisol levels in infants and young children. Children with secure attachments to their caregivers—even when emotionally upset—show stable cortisol levels, while even minor challenges raised cortisol levels among those in insecure relationships. She has shown the key ingredient to buffering stress is sensitive, responsive, individualized care, the type of care that leads to secure attachment relationships.

Stress in day care and preschool settings

Since the mid-1990s, Gunnar has studied cortisol levels when young children are in group care—day care and preschool. The most profound discovery was that 70–80 percent of children in center-based care show ever-increasing levels of cortisol across the day, with the biggest increases occurring in toddlers. By first grade, children don’t show these stress reactions to being with other children all day.

Gunnar has evidence that it is not separation from parents, but the experiences young children have in child care that produce these stress responses. “There is something about managing a complex peer setting for an extended time that triggers stress in young children,” says Gunnar.

In a study of family-based child care, Gunnar finds that children’s stress levels do not rise in settings where they receive a lot of attention, support, and guidance from the care provider, but do rise when they don’t. This is especially true of children with negative emotional temperaments. Gunnar is studying whether frequent increases in stress hormones at child care affect children’s emotional and cognitive development.

When Gunnar’s son entered preschool, she began to notice how much preschoolers care about fitting in and making friends. Her studies of preschoolers have shown that stress levels seem to be directly related to relationships with peers, and decrease as kids gain social competence.

“Negotiating friendships is very complicated,” says Gunnar. “It doesn’t appear that the child needs to be popular to maintain low stress, but it seems very important that they not be socially rejected.” Gunnar is conducting ongoing preschool studies that focus on understanding how a child’s temperament, relationships, and social skills impact their stress level.

Brain development among children adopted from orphanages and foster care

A major question is whether early neglect has long-term effects on children’s stress, emotion, and cognitive functioning. Through grants from the National Institutes of Mental Health, Gunnar has been studying children adopted internationally from foster and orphanage care. Using a registry of over 3,000 Minnesotan internationally-adopted children, she and her colleagues are studying whether early deprivation has long-term effects on specific brain regions involved in emotion and behavior regulation.

She hopes the project will discover information that could lead to interventions to help these children reach their full emotional and intellectual potential.

What others say about this research

W. Thomas Boyce, professor of epidemiology and child development, University of California-Berkeley, says, “Her research has been fundamental to an emerging vision of biology-environment interplay in disorders of early development and behavior, and has deepened early childhood educators’ understanding of and responses to the differences between young children.”

“Megan has taught the fields of developmental neuroscience, psychology, and psychopathology the importance of examining neurobiological stress systems in their research,” says Dante Cicchetti, psychology professor at the University of Rochester and director of the Mt. Hope Family Center, Rochester, NY, who studied stress in maltreated children with Gunnar. “Her research has shown that differential experiences can exert varied effects on brain development and child adaptation.”

Why this research matters

With nearly 60 percent of American women working outside the home, most young children spend much of their day in child care, where many first learn to interact with peers, establish relationships with adults other than their parents, and learn social skills like sharing, waiting, and cooperating.

“In the United States, there is no standardized system for maintaining high quality child care settings,” says Gunnar. “My research shows on a physical level—as others have shown on a behavioral level—that children who experience poor-quality care in their early life are at risk for poor developmental outcomes.”

Gunnar’s ongoing research can provide families and policymakers information vital to making the best care decisions for children, such as standards for low-stress day care settings, and guidelines to help parents select the best type of care for their child’s temperament. This research continues to shed light on how quality child care directly influences brain development among children.

January 2005