title: Variable cortisol circadian rhythms in children with autism and anticipatory stress.
abstract: OBJECTIVE
  Autism is characterized by impairment in communication and social interaction, by repetitive behaviours and by difficulty in adapting to novel experiences. The objective of the current investigation was to replicate and extend our previous findings showing variable circadian rhythm and significant elevations in cortisol following exposure to a novel stimulus (mock magnetic resonance imaging [MRI]).
  
  
  METHODS
  Circadian rhythms of cortisol were estimated in 22 children with and 22 children without autism via analysis of salivary samples collected in the morning, afternoon and evening over 6 separate days. We assessed hypothalamic-pituitary-adrenal (HPA) responsiveness by examining changes in salivary cortisol in response to a mock MRI. One-half of the children were re-exposed to the MRI environment.
  
  
  RESULTS
  Children with autism showed a decrease in cortisol in the morning over 6 days while maintaining higher evening values. Children with autism also showed more within-and between-subject variability in circadian rhythms. Although the cortisol values tended to be higher in some of the children with autism, a statistically significant elevation in cortisol in response to the initial mock MRI was not observed. Rather, both groups showed heightened cortisol at the arrival to the second visit to the imaging centre, suggesting an anticipatory response to the re-exposure to the mock MRI.
  
  
  CONCLUSIONS
  Children with autism showed dysregulation of the circadian rhythm evidenced by variability between groups, between children and within individual child comparisons. Both groups demonstrated increased salivary cortisol in anticipation of re-exposure to the perceived stressor.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, The M.I.N.D. Institute, Sacramento, CA 95817, USA. blythe.corbett@ucdmc.ucdavis.edu
authors.forename: Blythe A
authors.initials: BA
authors.lastname: Corbett
authors.forename: Sally
authors.initials: S
authors.lastname: Mendoza
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Wegelin
authors.forename: Vanessa
authors.initials: V
authors.lastname: Carmean
authors.forename: Seymour
authors.initials: S
authors.lastname: Levine
mesh_terms: D001321:Autistic Disorder / Q000378:metabolism* / Q000523:psychology*; D002648:Child; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis / Q000378:metabolism*; D007030:Hypothalamo-Hypophyseal System / Q000033:anatomy & histology / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D010913:Pituitary-Adrenal System / Q000033:anatomy & histology / Q000378:metabolism; D012463:Saliva / Q000737:chemistry; D013315:Stress, Psychological / Q000523:psychology*; D013997:Time Factors
chemical_list: D006854:Hydrocortisone