Some of the teens had changed to one particular gene—the glucocorticoid receptor (GR)—that helps regulate the body's hormonal response to stress.

This methylation of GR appears to make the individual more tuned in or sensitized to stress, so they will react to it quicker mentally and hormonally.

When the babies were followed up one to two decades later as adolescents, they had changes in the genetics of their GR that other teenagers did not.