Rachael Anyim

RACHAEL ANYIM, then a graduate student at State University of New York, Binghamton, New York, was awarded a grant in April 2023 to aid research on “Maternal Physical and Social Predictors of Variation in Human Milk Cortisol,” supervised by Dr. Katherine Wander. Physical and psychosocial stressors, and how individuals cope with stress, can lead to adaptations that shape physiologies and developmental trajectories. Stressors and subsequent coping responses can manifest as variation in human milk composition. Milk constituents (e.g., cortisol) can signal information regarding mother-infant dyads’ environment allowing infants to curate appropriate phenotypes suited to prevailing conditions. However, to reliably signal these conditions, milk cortisol should not vary with short-term stressors. This study tested predictions from life history theory that milk cortisol would be robust to transient stress (e.g., poor sleep) and vary with long-term stress (e.g., low socioeconomic status, height/BMI) and behavioral coping responses (e.g., problem-focused, emotion-focused, avoidant-focused). Short-term (e.g., sleep quality, daily uplifts) and long-term (e.g., BMI, education achieved, job-related buffering) conditions, and avoidant-focused coping (e.g., denial) predicted milk cortisol. Among these, greater job-related buffering (e.g., supportive environments) predicted larger infant height-for-age (HAZ), while greater daily uplifts (i.e., anything that brought participants satisfaction) and increased reliance on avoidant-focused coping predicted smaller HAZ. These results suggest milk cortisol signals increased maternal capital (e.g., support) to invest in infants, and reduced capital stemming from changes in maternal physiological (BMI) and psychological/emotional (e.g., satisfaction, avoidant coping) states, all of which can affect infant development.