1 Pediatric Public Health Psychology Laboratory, Centre for Clinical Research in Health, Department of Psychology, Concordia University, 7141 Sherbrooke Street West, SP-244, Montreal, QC H4B 1R6, Canada.
2 Pediatric Public Health Psychology Laboratory, Centre for Clinical Research in Health, Department of Psychology, Concordia University, 7141 Sherbrooke Street West, SP-244, Montreal, QC H4B 1R6, Canada. Electronic address: jennifer.mcgrath@concordia.ca.
3 Centre for Clinical Research in Health, Department of Psychology, Perform Center, Concordia University, 7141 Sherbrooke Street West, SP-244, Montreal, QC H4B 1R6, Canada.

Recent evidence suggests that poor sleep is a potential pathway underlying the association between stressful experiences and the diurnal cortisol profile. However, existing findings are largely limited to adults. The present study examines whether poor sleep (duration, quality) mediates the relation between stressful experiences and the diurnal cortisol profile in children and adolescents. Children and adolescents (N = 220, M(age) = 12.62) provided six saliva samples over two days to derive cortisol indices (bedtime, AUCAG, AUCTG, slope(MAX)). Perceived stress, stressful life events, self-reported sleep duration, and sleep quality were measured. Using bootstrapping analyses, sleep quality mediated the relation between perceived stress and AUCTG (R(2) = 0.10, F(7, 212) = 3.55, p = .001; 95% BCI[0.09, 1.15]), as well as the relation between stressful life events and AUCTG (R(2) = 0.11, F(7, 212) = 3.69, p = .001; 95% BCI[0.40, 3.82]). These mediation models remained significant after adjusting for sleep duration, suggesting that poor sleep quality underlies the association between stressful experiences and the diurnal cortisol profile in children and adolescents. Longitudinal data combined with objectively-measured sleep is essential to further disentangle the complex association between sleep and stress.