Evidence of a unique and common genetic etiology between the CAR and the remaining part of the diurnal cycle: A study of 14 year-old twins

Abstract

Introduction: By and large, studies have reported moderate contributions of genetic factors to cortisol secreted in the early morning and even smaller estimates later in the day. In contrast, the cortisol awakening response (CAR) has shown much stronger heritability estimates, which prompted the hypothesis that the etiology of cortisol secretion may vary according to the time of day. A direct test of this possibility has, however, not yet been performed. Objective: To describe the specific and common etiology of the CAR, awakening level and cortisol change from morning to evening in an agehomogenous sample of twin adolescents. Methods: A total of 592 participants of the Québec Newborn Twin Study, a population-based 1995-1998 cohort of families with twins in Canada, have collected saliva at awakening, 30 minutes later, at the end of afternoon and in the evening over four collection days.Results: Multivariate Cholesky model showed both specific and common sources of variance between the CAR, awakening and cortisol diurnal change. The CAR had the strongest heritability estimates, which, for the most part, did not overlap with the other indicators. Conversely, similar magnitudes of genetic and environmental contributions were detected at awakening and for diurnal change, which partially overlapped. Conclusion: Our study unraveled differences between the latent etiologies of the CAR and the rest of the diurnal cycle, which may contribute to identify regulatory genes and environments and detangle how these indicators each relate to physical and mental health.

Hair Cortisol in Twins: Heritability and Genetic Overlap with Psychological Variables and Stress-System Genes

“…While stressful environmental factors play a major role in HPA axis activation, twin studies have indicated that genetic factors have a substantial impact on the secretion of cortisol, especially morning cortisol. Predominantly moderate heritability estimates have been reported in adults (as reviewed in refs 25 – 27 ) and adolescents 25 , 27 , 28 . The observed heritability of HPA axis regulation suggests a contribution of genetically determined biological mechanisms.…”

Maternal cortisol slope at 6 months predicts infant cortisol slope and EEG power at 12 months

“…In addition to effects of caregiving and the psychosocial environment, physiological attunement could also reflect shared genes. Approximately 30% of the variance in waking cortisol is attributed to genetic influences (Bartels, Geus, Kirschbaum, Sluyter, & Boomsma, ; Ouellet‐Morin et al, , ; Van Hulle, Shirtcliff, Lemery‐Chalfant, & Goldsmith, ) while little to 0% of afternoon or evening cortisol is attributable to genetics (Bartels et al, ; Schreiber et al, ; Van Hulle et al, ). Further about 30% of cortisol slope is explained by genetics (Ouellet‐Morin et al, ; Van Hulle et al, ), potentially due to the genetic influence on waking levels.…”

“…Approximately 30% of the variance in waking cortisol is attributed to genetic influences (Bartels, Geus, Kirschbaum, Sluyter, & Boomsma, ; Ouellet‐Morin et al, , ; Van Hulle, Shirtcliff, Lemery‐Chalfant, & Goldsmith, ) while little to 0% of afternoon or evening cortisol is attributable to genetics (Bartels et al, ; Schreiber et al, ; Van Hulle et al, ). Further about 30% of cortisol slope is explained by genetics (Ouellet‐Morin et al, ; Van Hulle et al, ), potentially due to the genetic influence on waking levels. However, most studies have been with older children (Bartels et al, ; Ouellet‐Morin et al, ; Schreiber et al, ; Van Hulle et al, ), with only one infant study that involved one waking sample on a single day (Ouellet‐Morin et al, ).…”

“…Further about 30% of cortisol slope is explained by genetics (Ouellet‐Morin et al, ; Van Hulle et al, ), potentially due to the genetic influence on waking levels. However, most studies have been with older children (Bartels et al, ; Ouellet‐Morin et al, ; Schreiber et al, ; Van Hulle et al, ), with only one infant study that involved one waking sample on a single day (Ouellet‐Morin et al, ).…”

Changing environments reveal innovative genetic variation in children’s cortisol responses

“…The majority of previous studies investigating genetic variation of cortisol secretion have examined static cortisol levels rather than changes in cortisol over time (Rietschel et al, 2017;Tucker-Drob et al, 2017). The few studies that have examined the contribution of genetic variation to cortisol reactions or diurnal change have reported sizable heritability estimates (Federenko, Nagamine, Hellhammer, Wadhwa, & Wüst, 2004;Ouellet-Morin et al, 2016;Van Hulle, Shirtcliff, Lemery-Chalfant, & Goldsmith, 2012). It remains unknown whether heritable contributions to cortisol response simply reflect magnification of standing genetic contributions to baseline variation in cortisol, or whether there are novel contributions of genetic factors not evident prior to stressor onset.…”