title: Repeated salivary daytime cortisol and onset of mood episodes in offspring of bipolar parents.
abstract: BACKGROUND
  Differences in cortisol secretion may differentiate individuals at high compared to low genetic risk for bipolar disorder (BD) and predict the onset or recurrence of mood episodes. The objectives of this study were to determine if salivary cortisol measures are: (1) different in high-risk offspring of parents with BD (HR) compared to control offspring of unaffected parents (C), (2) stable over time, (3) associated with the development of mood episode onset/recurrence, and (4) influenced by comorbid complications.
  
  
  METHODS
  Fifty-three HR and 22 C completed salivary cortisol sampling annually for up to 4 years in conjunction with semi-structured clinical interviews. The cortisol awakening response (CAR), daytime cortisol [area under the curve (AUC)], and evening cortisol (8:00 p.m.) were calculated.
  
  
  RESULTS
  There were no differences in baseline CAR, AUC and evening cortisol between HR and C (p = 0.38, p = 0.30 and p = 0.84), respectively. CAR, AUC and evening cortisol were stable over yearly assessments in HR, while in Cs, evening cortisol increased over time (p = 0.008), and CAR and AUC remained stable. In HR, AUC and evening cortisol increased the hazard of a new onset mood disorder/recurrence by 2.7 times (p = 0.01), and 3.5 times (p = 0.01), respectively, but this was no longer significant after accounting for multiple comparisons.
  
  
  CONCLUSIONS
  Salivary cortisol is stable over time within HR offspring. However, between individuals, basal salivary cortisol is highly variable. More research is needed, with larger samples of prospectively studied HR youth using a more reliable method of cortisol measurement, to determine the potential role of cortisol in the development of mood disorders.
authors.affiliation: Department of Epidemiology, Dalla Lana School of Public Health, University of Toronto, 155 College St, Toronto, ON, M5T 3M7, Canada. Sarah.goodday@mail.utoronto.ca.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Goodday
authors.affiliation: Department of Mathematics & Statistics, University of Guelph, Guelph, ON, Canada.
authors.forename: Julie
authors.initials: J
authors.lastname: Horrocks
authors.affiliation: Department of Mathematics & Statistics, University of Guelph, Guelph, ON, Canada.
authors.forename: Charles
authors.initials: C
authors.lastname: Keown-Stoneman
authors.affiliation: Department of Psychiatry, University of Toronto, Toronto, ON, Canada.|Mood Disorders Centre of Ottawa, Ottawa University Health Services, Ottawa, ON, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Grof
authors.affiliation: Department of Psychiatry, University of Toronto, Toronto, ON, Canada.|Mood Disorders Centre of Ottawa, Ottawa University Health Services, Ottawa, ON, Canada.|Department of Psychiatry, University of Calgary, Calgary, AB, Canada.
authors.forename: Anne
authors.initials: A
authors.lastname: Duffy
keywords: Bipolar disorder; Cortisol; High-risk offspring; Hypothalamic pituitary adrenal axis; Mood disorders; Pathophysiology