title: Heritability of cortisol regulation in children.
abstract: BACKGROUND
  The normal development of cortisol regulation during childhood is thought to be influenced by a complex interplay between environmental and genetic factors.
  
  
  METHODS
  The aim of this study was to estimate genetic and environmental influences on basal cortisol levels in a sample of 151 twin pairs aged 9-16 years. Salivary cortisol was collected on two consecutive days when the children attended school--immediately after awakening, 30 min post-awakening and at bedtime.
  
  
  RESULTS
  Heritability was highest (60%) for cortisol levels about 30 min after awakening. For samples taken immediately at awakening heritability was less pronounced (28%) and in the evening low (8%).
  
  
  CONCLUSIONS
  The limited genetic influence on evening levels, moderate on cortisol at awakening and high on awakening response, might imply two genetic regulation patterns, one specifically for awakening response and one for the circadian rhythm proper. These findings could explain divergent results in previous studies and highlight the importance of taking the circadian rhythm into account in studies of cortisol levels in children.
authors.affiliation: Department of Clinical and Experimental Medicine, Child and Adolescent Psychiatry, Linköping University, Sweden. Per.A.Gustafsson@liu.se
authors.forename: Per A
authors.initials: PA
authors.lastname: Gustafsson
authors.forename: Per E
authors.initials: PE
authors.lastname: Gustafsson
authors.forename: Henrik
authors.initials: H
authors.lastname: Anckarsäter
authors.forename: Paul
authors.initials: P
authors.lastname: Lichtenstein
authors.forename: Therese
authors.initials: T
authors.lastname: Ljung
authors.forename: Nina
authors.initials: N
authors.lastname: Nelson
authors.forename: Henrik
authors.initials: H
authors.lastname: Larsson
mesh_terms: D000293:Adolescent; D002648:Child; D002940:Circadian Rhythm / Q000235:genetics; D004777:Environment; D005260:Female; D005786:Gene Expression Regulation; D059647:Gene-Environment Interaction; D006801:Humans; D006854:Hydrocortisone / Q000097:blood* / Q000235:genetics*; D008297:Male; D019655:Quantitative Trait, Heritable; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics
chemical_list: D006854:Hydrocortisone