Numerous studies have linked high levels of the stress hormone cortisol to depression, obesity, heart attacks and other health problems. Despite acknowledging its theoretical importance, few researchers, have looked at the effects of chronically low levels of cortisol, says Sarah Watamura, PhD, of the University of Denver.

That’s in part because researchers don’t see many cases of low cortisol, aside from adults with post-traumatic stress disorder, she says. Yet in a study of 120 low-income Denver preschoolers, Watamura found 18 children with potentially dangerously low levels of the hormone — levels that stayed low all day. These children do react behaviorally to stress, she says — they cry and get upset — but they aren’t responding physiologically, so they aren’t getting the cortisol bump they need to manage stressful situations.

Now, with a $20,000 Visionary Grant from the American Psychological Foundation, Watamura is tracking these children, who are now 5 to 8 years old, and retesting their cortisol levels to explore the health and cognitive effects of having too little of the hormone and whether the deficit is due to chronic stress or something else, such as undiagnosed asthma.

So far, Watamura has found that children with low cortisol levels often show early signs of depression, anxiety and delayed physical development. She’s advocating that such children receive programs to help buffer their stress. One way to do that would be to train preschool teachers to help children manage their emotions, says Watamura, who taught preschool before becoming a psychologist. Research shows that children are adept at learning stress-management techniques from adult caregivers, she says.

“The most important thing that we can do to buffer stress at preschool is to strengthen teachers’ relationship-building behaviors, particularly those important for secure attachment, such as emotional availability, good communication, clear expectations and consistency,” says Watamura.