HPA axis reactivity in early childhood: associations with symptoms and moderation by sex.

Sex differences in rates of internalizing disorders have been attributed in part to heightened sensitivity to stress in females. While the sex difference in disorder rates becomes most pronounced in adolescence, developmental research suggests that stress reactivity in girls may be related to elevated internalizing symptoms even in childhood. We therefore examined whether child sex moderated associations between symptoms of psychopathology and cortisol reactivity to a standardized stress task in 409 three-year-old community-dwelling children. Anxious symptoms were associated with elevated cortisol reactivity, but only in girls. Externalizing symptoms were unrelated to baseline cortisol or cortisol reactivity, and no evidence for moderation by child sex was found. Results suggest that cortisol reactivity to stress in early childhood has a sex-specific association with girls' internalizing symptoms.