Stress hormone linked to learning delay in toddlers

"Some of these kids are already behind before they start kindergarten, and there is research that shows that they're unlikely to catch up," says Jennifer Suor. (Credit: Jason Farrar/Flickr)

Little kids who live in stressful family situations often have too little or too much cortisol, a hormone that can have toxic effects on the brain.

A study of 201 low-income mother-child pairs conducted at Mt. Hope Family Center in Rochester, NY, tracked the levels of the stress hormone cortisol in children at ages 2, 3, and 4.

The findings show that specific forms of family adversity are linked to both elevated and low levels of cortisol in children. Kids with either elevated or low cortisol levels showed lower than average cognitive ability at age 4.

“What we were interested in seeing is whether specific risk factors of children living in poverty might be related to children’s cortisol levels,” says lead author Jennifer Suor, a PhD candidate in clinical psychology at University of Rochester. “Then we looked to see if the hormone levels are predictive of significant differences in the children’s ability to think.”

Too much or too little cortisol

The study, published in the journal Child Development, shows that children in low-income, stressful home environments—specifically homes with family instability and harsh and disengaged mothers—may have adverse levels of cortisol in their bodies, which has been linked to damaging effects on the structure and function of children’s brains.

Understanding how cortisol affects the brain’s cognitive abilities, though, remains unclear.

“The exact mechanisms through which too much or too little cortisol affects cognitive functioning aren’t fully understood,” says coauthor Melissa L. Sturge-Apple, assistant professor of psychology.

“Researchers hypothesize that too much cortisol can have toxic effects on parts of the brain that are important for cognitive functioning, and too little might hinder the body’s ability to recruit the biological resources necessary for optimal cognitive functioning.”

Suor says moderate amounts of cortisol are ideal. “In the right amount it makes you rise to the occasion and it helps recruit important cognitive resources like memory and the ability to reason. But it’s a problem when we have too much or too little cortisol.”

Behind before kindergarten

The children with family instability or harsh and emotionally distant caregivers at age 2 had elevated cortisol levels, while children with only family instability at age 2 had lower than average cortisol levels.

“We were surprised to find that the children’s cortisol levels, which we test from a cheek swab, didn’t change—they remained relatively stable over the three years,” Suor says.

Family instability includes frequent changes in care providers, household members, or residence. This kind of instability can reflect a general breakdown of a family’s ability to provide a predictable and stable environment for the child.

“There are other environmental and biological factors that might contribute to children’s lower cognitive functioning. However, our research, as well as previous studies, has indicated that cortisol plays a role in cognitive functioning.”

“We saw really significant disparities in the children’s cognitive abilities at age four—right before they enter kindergarten,” Suor says. “Some of these kids are already behind before they start kindergarten, and there is research that shows that they’re unlikely to catch up.”


Prevention and intervention could help these at-risk children. “Our findings support the need for an investment in community-based interventions that can strengthen parent-child relationships and reduce family stress very early in a child’s life,” Suor says.

“A lot of research that we’ve done at Mt. Hope shows that using preventative interventions can help moms parent their children in ways that may lead to improvements in their children’s cortisol.”

Researchers at the University of Minnesota and Mt. Hope Family Center coauthored the study. The National Institute of Mental Health supported the work.

Source: University of Rochester