May 2012 in “Neurotoxicology and Teratology” Hair cortisol can be a reliable way to measure long-term stress.
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September 2018 in “Clinical Biochemistry” Hair cortisol analysis can help diagnose stress-related conditions but needs more refinement for widespread use.
May 2023 in “Animal Reproduction Update” High levels of cortisol in hair show long-term stress which can lower fertility in animals.
December 2025 in “Biology Bulletin Reviews” Hair cortisol can indicate animal stress but varies with many factors.
January 2026 in “Western Journal of Nursing Research” Hair cortisol levels don't reliably indicate chronic stress in people with multiple sclerosis.