Environmental lighting, behavioral state, and hormonal response in the newborn.

This experimental study was designed to investigate the effects of constant and intermittent light on newborn infants. Changes in levels of salivary cortisol were utilized as indications of increased pituitary-adrenal activity. The sample consisted of 99 babies who were classified as state predominance sleep (Group A) babies or state predominance awake (Group B) babies following a 3-hour observation period for each infant. The experimental group was subjected to intermittent light and the control group to constant overhead lighting on two consecutive nights. A 2 X 2 ANOVA utilizing absolute change salivary cortisol scores revealed a statistically significant interaction between light and state. The findings suggest that the effects of different light conditions are related to individual response differences. In intermittent light, the absolute change salivary cortisol scores may reflect a previously assumed unobservable cortisol rhythmicity in Group B babies and a diminution of stress in Group A babies.