Changes in hair cortisol among Brazilian adolescents before and during the COVID-19 pandemic

Abstract

Abstract Adolescence is a sensitive developmental period marked by increased reactivity of the HPA axis to environmental stressors. However, little is known about how chronic cortisol levels change during prolonged adversity. Using the COVID-19 pandemic as a natural experiment, this study examines how large-scale environmental disruption affects HPA-axis regulation during adolescence. We investigated hair cortisol concentration (HCC) pre- and during the pandemic in adolescents from Pelotas, Brazil, and identified predictors for change. Data were drawn from the 2004 Pelotas Birth Cohort, a population-based longitudinal study. Hair samples (3 cm) were collected at the 15-year pre-pandemic assessment (T1; 2019–2020) and again at the 17-year mid-pandemic assessment (T2; 2021). HCC was quantified via ELISA method. Socioeconomic, demographic, and pandemic-related experiences, as well as self-reported stress levels, were assessed as potential determinants of changes in HCC. A multivariate latent change score (LCS) model was used to analyze changes in HCC and their associations with predictors. A total of 1,509 individuals were included in the analyses. There was a significant mean increase in HCC of 1.89 pg/mg ( p < 0.001) from T1 to T2. Pandemic-related experiences, such as maternal job loss ( p = 0.005) and higher levels of perceived stress ( p = 0.041), were associated with greater increases in HCC. Government cash transfer program participation ( p < 0.001), having a black or mixed-race mother ( p = 0.017), and being female ( p < 0.001) were associated with lower increases in HCC. Findings suggest significant physiological effects of the COVID-19 pandemic, highlighting the role of demographic, socioeconomic, and pandemic-related factors in shaping cortisol responses and advancing understanding of its impact on adolescent health, with implications for policy and support in low- and middle-income countries. These findings highlight the intricate relationship between cortisol changes and psychological outcomes across various populations during the pandemic.

The authors' abstract, as published at the source. Scientific Reports, 2026 · DOI ↗