Preliminary Indications That First Semester Students From Academic Households Exhibit Higher Hair Cortisol Concentrations Than Their Peers From Nonacademic Households

Comparison of human hair cortisol concentration stability for 1-year and 2-year test-retest intervals

Human hair cortisol concentration (HCC) has previously been found to be highly stable for a 1-year interval (r = 0.73) in terms of a product-moment correlation. The present study aimed to replicate this finding and compare HCC stability regarding 1-year and 2-year test-retest intervals. Female university students (N = 39) provided hair strands twice (t1 and t2) at intervals of 1 (n = 21) or 2 years (n = 18). Multiple regression analysis predicting HCC at t2 revealed a significant interaction term (HCC at t1 × time interval condition). It was determined that HCCs were substantially related for the 1-year interval but unrelated for the 2-year interval. The findings were not attributable to potential influences, such as hair treatment. The product-moment correlation showed nearly identical consistency with previous research regarding the 1-year test-retest interval. There was no significant product-moment correlation for the 2-year interval. Overall, these findings indicate that within a temporal framework of 1 year, HCCs may be stable predictors in correlational studies where the focus is on the rank orders of measured values.

The Relationship Between Family Socioeconomic Status and Adolescent Sleep and Diurnal Cortisol

OBJECTIVE

This study aimed to investigate the associations between indices of family socioeconomic status and sleep during adolescence and to examine whether measures of hypothalamic-pituitary-adrenal (HPA) axis functioning mediate the observed associations.

METHODS

A total of 350 ethnically diverse adolescents (57% female; mean [standard deviation] age wave 1 = 16.4 [0.7] years) completed a three-wave longitudinal study in which sleep and cortisol data were collected at 2-year time intervals. Sleep duration, latency, and variability were assessed via actigraphy during a period of 8 days per study wave. Salivary cortisol was collected across 3 days per study wave to assess cortisol diurnal slope, area under the curve, and the cortisol awakening response. Adolescents' caregivers reported their education levels, family income, and economic hardship.

RESULTS

A greater family income-to-needs ratio was associated with longer adolescent sleep duration ( b = 2.90, p = .023), whereas greater parental education was associated with shorter sleep duration ( b = -3.70, p = .030), less sleep latency ( b = -0.74, p = .016), and less variability across days ( b = -2.06, p = .010). Diurnal cortisol slope statistically mediated the association of parental education with sleep duration ( b = -0.48, 95% confidence interval = -1.099 to -0.042), but not the association of income-to-needs ratio with sleep duration.

CONCLUSIONS

Findings suggest that parental education and family resources may have unique impacts upon sleep and HPA axis functioning during the period of adolescence. Future research is needed to examine family and behavioral factors that may underlie socioeconomic status associations with adolescent sleep and HPA axis functioning.