Methodological Considerations for Hair Cortisol Analysis: Effects of Resuspension Solution, Hair Weight, Extraction Duration, and Degree of Hair Shredding on Hair Cortisol Concentrations

This study addresses methodological factors affecting hair cortisol concentration (HCC) analysis, which is crucial for understanding long-term cortisol secretion related to stress and health. The research investigates the impact of resuspension solutions, hair weight, extraction duration, and hair shredding on HCC. Experiment 1 compares ultra-pure water and phosphate buffer for resuspension, while Experiment 2 examines the effect of hair sample weight (5 mg, 7.5 mg, 10 mg) on HCC. Experiment 3 explores extraction durations (20, 24, 72 hours) to determine optimal cortisol extraction time, and Experiment 4 assesses how different hair-cutting methods influence cortisol extraction. The study highlights the need for standardized protocols due to variability in practices across laboratories, as current findings on these factors are inconclusive.