Hair cortisol concentration (HCC) is a promising biomarker for chronic stress, yet its relationship with subjective distress and mental health remains unclear. Existing research has largely focused on group-level data over relatively short time frames. In the present longitudinal case study, we tracked HCC and subjective measures in a female PhD student across nine years (2014–2023), including depression severity, trait anxiety, resilience, coping strategies, and life events. Her data were compared with HCC, depression, and anxiety levels in a clinical outpatient sample (N = 33) and normative HCC data. Despite reporting numerous stressful life events, the PhD student’s HCC levels remained stable and comparable to the clinical sample, and the norm, with the exception of for a marked elevation during the first month of the PhD (HCC = 12.18 pg/mg; p < .001). She showed exceptionally high resilience (M = 4.7, p < .001) and use of problem-focused coping strategies (PR = 97.9), and low avoidant coping (PR = 28.2). In the clinical sample, HCC was not associated with diagnosis, depression severity, or trait anxiety. These findings suggest that HCC may not serve as a straightforward biomarker of psychological distress or reliably differentiate between clinical and non-clinical individuals. Instead, HCC appears to reflect a complex, context-dependent measure influenced by methodological and behavioral factors.
Hollandt et al. (Wed,) studied this question.