Hair cortisol as a measure of the stress response to social adversity in young children.

Hair cortisol has the potential to provide insight into young children's long-term stress response to social adversity. This study investigated associations between children's exposure to adversity from pregnancy to 2 years of age and their hair cortisol at 2 years, using a longitudinal cohort of children enriched for adversity risk, whose mothers were recruited during pregnancy through the "right@home" trial. Exposures were 18 maternal socioeconomic and psychosocial indicators of adversity, examined as concurrent, cumulative, and longitudinal exposure from pregnancy to 2 years. Hair samples were analyzed from 319/603 (53%) children participating at 2 years. Multivariable regression analyses for concurrent exposure showed three indicators of adversity were associated with higher hair cortisol (housing tenure of public rental, paying board or living rent free; not living in a safe place; higher maternal stress symptoms), one with lower hair cortisol (housing problems), and 14 indicators with no evidence of association. There was no evidence of association for the cumulative adversity count. Longitudinal exposure showed "intermittent" and "persistent" high maternal stress symptoms were associated with higher hair cortisol. The small number of associations identified suggests that hair cortisol is limited as a measure of stress response to social adversity in children at 2 years.