Urinary cortisol excretion rates and anxiety in normal 1-year-old infants

Urinary cortisol excretion rates were determined for each voiding during 8 hours on 3 days for 20 infants. The first day served as the control. On the second day stress was imposed by having the mother leave the infant for an hour. On a third day the child was stimulated by novel toys and socialization for an hour in the mother's presence. There was no significant difference between mean cortisol excretion rates on control and stress days. Variability in cortisol levels was significantly greater on the day of stress than on the other 2 days. Ratings of separation anxiety and levels of cortisol excreted 40 to 160 min after the imposed stress were positively correlated (r = 0.46, P less than 0.01). Cortisol levels also differentiated between anxious infants who were agitated from those who were withdrawn. No altered levels of cortisol were associated with excitement.