Gender is Key: Girls' and Boys' Cortisol Differs as a Factor of Socioeconomic Status and Social Experiences During Early Adolescence.

The risks associated with negative peer relationships and low socioeconomic status (SES), and how they impact diurnal cortisol and the cortisol response to negative experiences, have never been studied together in early adolescents; this study aims to fill this gap in the literature. Saliva was collected from 95 early adolescents (Mage = 10.80, SD = 0.72) and daily diaries were completed 30 min after awakening, beginning of school, 15 min after first recess, 15 min after lunch, and at the end of the school day across four consecutive days. Hierarchical Linear Modelling was used to estimate the within- and between-person variances of diurnal cortisol and the cortisol response to stress in the context of SES and peer experiences. Cortisol secretion differed by gender and was predicted by SES and social status within the peer group. Low-SES early adolescents had higher morning cortisol. Girls who were from higher SES families had the steepest diurnal cortisol slope. Non-accepted early adolescents had low cortisol in response to both positive and negative social experiences. The findings from this study clarify the impact of both SES and peer relations on early adolescent psychophysiological development.