Early psychosocial exposures, hair cortisol levels, and disease risk.

BACKGROUND Early psychosocial exposures are increasingly recognized as being crucial to health throughout life. A possible mechanism could be physiologic dysregulation due to stress. Cortisol in hair is a new biomarker assessing long-term hypothalamic-pituitary-adrenal axis activity. The objective was to investigate whether early-life adverse psychosocial circumstances influence infant cortisol levels in hair and health outcomes in children prospectively until age 10. METHODS A cohort study in the general community using a questionnaire covering 11 psychosocial items in the family during pregnancy and the cumulative incidence of diagnoses until age 10 years in 1876 children. Cortisol levels in hair were measured by using a radioimmunoassay in those with sufficient hair samples at age 1, yielding a subsample of n = 209. RESULTS Children with added psychosocial exposures had higher infant cortisol levels in hair (B = 0.40, P < .0001, adjusted for gender and size for gestational age) in a cumulative manner and were significantly more often affected by 12 of the 14 most common childhood diseases, with a general pattern of increasing odds ratios. CONCLUSIONS The findings support the model of physiologic dysregulation as a plausible mechanism by which the duration and number of early detrimental psychosocial exposures determine health outcomes. The model indicates that the multiplicity of adversities should be targeted in future interventions and could help to identify children who are at high risk of poor health. Furthermore, given the prolonged nature of exposure to a stressful social environment, the novel biomarker of cortisol in hair could be of major importance.