Hair Cortisol as a Biomarker of Chronic Stress in Community-Dwelling Adults With Longstanding Multiple Sclerosis.

The study was cross-sectional, so it cannot show whether stress, hair cortisol, or MS outcomes came first. The final analysis included only 75 participants, and the sample was mostly older, white, female, retired, and had longstanding MS. This restricts generalisability. Only 5 male participants were included, and the authors note that sex differences in hair cortisol may have affected the observed levels. The sample's median perceived stress was 12 on a 0 to 40 scale, which may have made a relationship with hair cortisol hard to detect. The study did not assess specific stressors, their duration, severity, or controllability. It did not control for alcohol use, smoking, detailed current medication use, or hair care practices that can influence hair cortisol. Hair cortisol and perceived stress covered different time windows, which makes direct comparison difficult. Self-collection adherence could not be verified, and some samples were unusable because of orientation loss, colored hair, or insufficient length or weight. The regression model was not significant overall, and subgroup analyses by MS type were also not significant, so the employment finding should be treated cautiously.

Do not read the 59.6% return rate as evidence that hair cortisol measures chronic stress in MS. It only shows that mailed self-collection was feasible; cortisol did not track perceived stress.