Measuring cortisol concentrations in hair and fingernails as biomarkers of stress in adolescents

Traditional approaches to understanding adolescent stress and development often rely on retrospective reports of major life events (e.g., ACE-IQ; WHO, 2018). While informative, these approaches emphasise the long-term impact of early adversity rather than how everyday stress shapes mental health during adolescence itself.

To address this gap, we are conducting a longitudinal study of adolescents (aged 11-15 years at intake) using an accelerated cohort design that combines ecological momentary assessment (EMA) with biosampling of hair and fingernail cortisol. EMA captures real-time data on emotional states, peer interactions, activities, and daily stressors in natural settings (Myin-Germeys et al., 2018). In parallel, cortisol from hair and nails provide a more stable, retrospective index of hypothalamic-pituitary-adrenal (HPA) axis activity over weeks to months (Stalder et al., 2012; Staufenbiel et al., 2013).

Our work in the formative phase of the study indicated that hair and nail collection methods are broadly feasible and well-tolerated among adolescents: 67% of older adolescents reported willingness to provide at least one of these sample types, with hesitations primarily related to uncertainty about biosample collections and concerns about altering appearance. Importantly, willingness to provide one sample positively predicted willingness to provide the other, indicating consistent attitudes towards various sample types.

During the pilot phase, 22 participants provided both hair and fingernail samples to assess comparability of cortisol concentrations across sample types, and to explore associations with subjective stress and mental health.

By integrating daily experiences with physiological stress, this approach can provide novel insight to the reciprocal links between daily experience and stress physiology that contribute to adolescent mental health. This understanding may contribute to developing strategies for early intervention.