The impact of COVID-19 pandemic and lockdown on chronic stress assessed by hair cortisol analysis via LC-MS/MS

Objectives The COVID-19 pandemic and associated lockdown measures have had profound effects on mental health worldwide. This study aimed to assess changes in long-term stress levels across three distinct time periods - pre-lockdown, during lockdown, and post-lockdown - by measuring cortisol concentrations in hair samples.Methods Hair samples were collected from 87 individuals referred to our forensic toxicology laboratory during 2020. When possible, each hair sample was segmented to reflect the pre-lockdown, lockdown, and post-lockdown periods. Cortisol, a validated biomarker of chronic stress, was quantified in each segment using a newly developed and fully validated liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method. Statistical comparisons between periods were performed using ANOVA followed by post hoc analyses.Results Cortisol concentrations showed a statistically significant increase in the post-lockdown period (median 3.68 pg/mg) compared to both pre-lockdown (median 2.28 pg/mg) and lockdown (median 3.06 pg/mg) periods. Subgroup analyses revealed that females and young adults (17-24 years) exhibited the most pronounced increases in cortisol levels across time points. Notably, 76 % of individuals with complete three-segment profiles showed higher cortisol concentrations in the post-lockdown period compared to pre-lockdown, suggesting a sustained psychological burden.Conclusions Hair cortisol analysis revealed a consistent elevation in stress biomarkers during and after the COVID-19 lockdown, particularly among females and younger individuals. These findings highlight the enduring psychosocial impact of the pandemic and support the use of segmental hair analysis as a powerful tool for retrospective assessment of chronic stress in population studies.