Association Between Intellectual Disability and Hair Cortisol Concentration in Adolescents in a Brazilian Population‐Based Birth Cohort

OBJECTIVE: Children with intellectual disability (ID) usually exhibit neuroendocrine functioning impairment, such as alterations in the hypothalamic-pituitary-adrenal (HPA) neuroendocrine axis, which can result in glucocorticoid cortisol release alterations. Indeed, many studies showed a positive association between ID and cortisol concentration. However, evidence is lacking on the relationship between child neurodevelopment and cortisol levels during adolescence in population-based studies. We aimed to test the association between ID and hair cortisol concentration (HCC) during adolescence in a prospective population-based cohort. METHODS: Data from 1770 individuals in the 2004 Pelotas Birth Cohort were used. ID was diagnosed at age 6 through clinical examination. Hair cortisol was measured at age 15. Association was assessed using linear regression models adjusted for sex, socio-economic factors, hair-related variables and corticosteroid use. RESULTS: Higher HCC were observed in individuals with ID (β: 1.120; 95% CI: 1.012, 1.241) in the analysis adjusted for sex, hair-related variables and corticosteroid use. Compared to the other aetiological groups, this was more evident in idiopathic ID. But this did not remain significant when demographics/socio-economic variables were controlled for. CONCLUSION: Children with ID, particularly those with idiopathic ID, might exhibit dysfunction in the HPA axis or experience heightened stress levels during adolescence.