The effect of socioeconomic status and 5-HTTLPR on preschoolers’ social competence and diurnal cortisol levels

Abstract

Social competence (SC) is an important contributor to children’s development and influenced by genetic and environmental factors. This study investigates the associations between socioeconomic status (SES), SC and Hypothalamic-Pituitary Adrenal (HPA) axis activity moderated by serotonin transporter polymorphism (5 HTTLPR) and sex. Preschool children (45-83 months), their mothers and teachers participated in the study. SC was assessed by teachers’ report of Social Competence and Behavior Evaluation Scale – Short Form. SES was calculated as the standardized average score of parental education and income. 5-HTTLPR genotype was determined from salivary DNA as Short/Short (SS), Short/Long (SL) and Long/Long (LL). HPA-axis activity was measured as salivary diurnal cortisol levels at daycare and home through a morning and an afternoon sample. A multilevel linear model testing the association between SES and SC revealed a significant three-way interaction between sex, SES and 5-HTTLPR. For SS boys and SL-LL girls, as SES increased, SC increased, while a reverse pattern was observed in LL boys and SS girls. For HPA-axis activity, only in boys, higher SC buffered the impact of SES on daycare diurnal slope. For boys with lower SC, those with SS genotype had decreased diurnal slopes with increased SES, while LL boys had decreased slopes with decreased SES. There were no significant associations for girls or high SC boys. These findings indicate for the first time the differential effects of SES on preschoolers’ SC and diurnal cortisol by sex and 5-HTTLPR. Future studies should investigate the associations between SES, SC and HPA-axis outcomes in a longitudinal fashion.