The Social, the Socio, and the HPA: How peer rejection, peer acceptance, and socioeconomic status relate to children’s HPA-axis activity

Understanding how socioeconomic status (SES) “gets under the skin” to impact health has puzzled researchers for decades. SES is a complex, multifaceted construct that can be examined using a variety of methodologies. Additionally, SES can impact diverse and interrelated spheres of development. This dissertation attempts to parse how SES and the peer group individually and additively impact children’s cortisol levels. Study 1 examines children’s cortisol at the beginning and end of their first year of kindergarten and finds that rejected children have flatter morning cortisol slopes, while lower SES children have higher cortisol at the end of the school year compared to their higher SES peers. Study 2 examines children’s diurnal cortisol and cortisol response to positive and negative peer experiences and finds that girls from lower income families have a flatter diurnal cortisol slope. It also found that children not accepted by their peers had little cortisol response to positive or negative peer experiences, while accepted children had elevated cortisol following positive peer experiences. Study 3 examines these same variables in relation to hair cortisol and found that children from a lower income background have higher hair cortisol, while low levels of parental education moderated the association between rejection and acceptance such that children from families with lower levels of parental education had low cortisol when they were rejected or not accepted and high cortisol when they were accepted or not rejected. Together, these sets of results highlight the importance of using multiple measures of SES to better understand its association with peer difficulties and cortisol. Understanding how social factors and SES impact the HPA-axis could inform intervention programs designed to help disadvantaged children