The unique contributions of negative emotionality and sleep problems to toddlers' physiological stress response

Previous research has examined temperament and sleep separately with respect to their relationship to young children's physiological stress response; however, little research has jointly investigated these two constructs in relation to children's physiological stress response. Previous research also has not considered the potential contributions of individual components of children's negative emotionality to their stress response. In the present study, mothers reported on children's negative emotionality and sleep problems when children were 18 and 24 months old respectively. When children were 30 months old, saliva samples were collected prior to and after the stranger approach task to assess physiological stress response as measured by total cortisol secretion (AUCg) and cortisol reactivity (AUCi). Results showed that frustration was positively associated with AUCg. Frustration and sleep problems were also both positively associated with AUCi, and shyness was negatively associated with AUCi. No other dimensions of negative emotionality were related to AUCg or AUCi. These results highlight the unique contributions of toddlers' temperament and sleep difficulties to their stress physiology. Furthermore, these results highlight the importance of parsing out the individual components of negative emotionality when conducting temperament research on children's stress response.