Characterizing the Individual: Hair Cortisol as a Biomarker of Mental Health and Functioning in a PhD Student Compared With a Clinical Sample

This longitudinal case study examined hair cortisol concentration (HCC) as a biomarker for chronic stress in a female PhD student over nine years, comparing her data with a clinical outpatient sample (N = 33) and normative HCC data. Despite experiencing numerous stressful life events, the student's HCC levels were stable and similar to the clinical sample and norm, except for a significant increase during the first month of her PhD. She exhibited high resilience and problem-focused coping, with low avoidant coping. In the clinical sample, HCC was not linked to diagnosis, depression severity, or anxiety. The study suggests that HCC may not be a straightforward biomarker for psychological distress, as it is influenced by various methodological and behavioral factors.