Negative life events, emotions and psychological difficulties as determinants of salivary cortisol in Belgian primary school children.

PURPOSE: This paper describes whether children's life events, emotions and psychological difficulties are related to their salivary cortisol patterns and whether this is different between sexes.
METHODS: In 385 children (5-10 years old) participating in the ChiBS study, salivary cortisol samples were collected when waking up, 30 min and 60 min after wake up and in the evening on two consecutive weekdays. Moreover, data on children's life events, emotions and difficulties were collected. Statistical analysis was done separately for boys and girls by multilevel growth curve modelling with adjustments for age, body mass index, socio-economic status and wake up time.
RESULTS: In boys and girls with more negative life events during the last three months, the diurnal cortisol slope was steeper (more decline). Boys with higher self-reported happiness showed lower overall, morning and evening cortisol levels. In contrast, the diurnal slope was steeper (more decline) in boys with emotional problems due to higher morning values. In girls, peer problems were associated with lower overall and morning cortisol levels.
CONCLUSIONS: Children's salivary cortisol patterns were related to some negative life events, emotions and difficulties, although differently in boys and girls. As such, sex-differences in HPA functioning are already present in young children. Most findings support the upregulation of the cortisol response to stress, although lower morning values were found in the presence of peer problems in girls. Future studies should focus on sex differences, positive emotions and the diurnal cortisol slope.