Psychobiological differences in childhood stress response. II. Cardiovascular markers of vulnerability.

A fuller understanding of the distribution of morbidity in childhood may be achieved through the study of individual differences in stress susceptibility. The importance of person-environment transactions has been appreciated in the psychological domain, but only recently have individual differences in children's psychobiological responsivity to the environment become the focus of systematic study. Current work on individual differences in children's biobehavioral stress response is illustrated by reviewing current research on two aspects of cardiovascular regulation: cardiovascular reactivity and cardiac vagal tone. Both show promise of being stable individual traits emerging early in childhood, and both have correlates with children's patterns of health, behavior, and development. Consideration of individual differences in children's physiological responsivity can enrich our understanding of the meaning and adaptive significance of childhood behavior.