New tool taps drool for clues to childhood stress

University Park, Pa. -- In four separate studies of mothers and their infants, preschoolers, kids and teens, a multi-university research team has shown, for the first time, that a simple test of a little drool can provide new insight into the role of social stressors, including relationships with parents and teachers, in child development.

The test monitors alpha amylase, an enzyme secreted by the salivary glands, that has been linked in adults to the sympathetic nervous system's (SNS) fight or flight response. Now, in these new studies, alpha amylase has been shown to be a marker for the SNS response in children, too.

The current findings suggest that social forces largely determine individual differences in alpha amylase levels. The social stressors used in the studies included babies being gently restrained by a stranger and the older children having to complete a frustrating task, interact with a teacher, or be evaluated. Social relationships with mothers and teachers also were found to influence alpha amylase levels.

Douglas A. Granger, associate professor of biobehavioral health and human development and family studies at Penn State, is first author of the team's recently published paper on the study. "Being able to monitor alpha amylase via a salivary test may open new opportunities to characterize individual differences in response to stress that we weren't able to see before. We think that these differences could prove to be meaningful in understanding behavior," he said.

The four studies are detailed in an invited paper, "Integrating the Measurement of Salivary Alpha-Amylase into Studies of Child Health, Development and Social Relationships," in a special issue of the Journal of Social and Personal Relationships published in April. The authors are Granger, Katie T. Kivlighan, doctoral candidate in biobehavioral health, and Clancy Blair, associate professor of human development and family studies, all at Penn State; Mona El-Sheikh, Jacquelyn Mize, Jared A. Lisonbee and Joseph A. Buckhalt in the Department of Human Development and Family Studies at Auburn University; Laura R. Stroud, Centers for Behavioral and Preventive Medicine, Brown Medical School; Kathryn Handwerger, Department of Psychology, Tufts University; and Eve B. Schwartz, Salimetrics LLC, State College, Pa.

The findings reported include the observation that mothers and their 6-month-old baby sons were "attuned" and had similar alpha amylase levels. Among the 8- and 9-year olds studied, there was a pattern of positive associations between alpha amylase and social problems, aggressive behavior and cognitive/academic problems. In addition, the researchers report that 4-year-old children with higher alpha amylase were more susceptible to illness and had less-close relationships with their preschool teachers. The associations between alpha amylase and illness were somewhat stronger for girls than for boys.

"The associations revealed between alpha amylase and illness susceptibility are particularly robust and worthy of comment. The finding is unique and is consistent with volumes of research on the linkages between the brain, behavior and immunity," the authors wrote.

The Penn State Behavioral Endocrinology Laboratory and the Penn State Child Youth and Families Consortium as well as the National Institute of Child Health and Development, National Science Foundation, Alabama Agricultural Experiment Station and a Lindsey Foundation Grant supported the study.

Granger developed the new salivary alpha amylase assay with a team of researchers at his company, Salimetrics LLC. Salimetrics assayed the alpha amylase samples used in the study.