Hair as a Retrospective Calendar of Cortisol Production—Increased Cortisol Incorporation into Hair in the Third Trimester of Pregnancy

This study analyzed cortisol levels in hair segments from 103 mothers with neonates, 19 mothers with toddlers, and 20 control women to test if hair can reflect past cortisol production. Results showed a strong decline in cortisol from the scalp to the distal hair segments, with a 30-40% decrease per segment. The first 3-cm segment of hair from mothers who had just given birth had twice the cortisol levels compared to controls, indicating increased cortisol during the third trimester. No significant differences were found in older hair segments. The study concluded that hair cortisol measurement can reflect increased cortisol production for up to six months, but not beyond due to rapid decline.