title: Neuroticism and cortisol: pinning down an expected effect.
abstract: BACKGROUND
  There are strong theoretical arguments that those high on Neuroticism (N) should normally exhibit higher prevailing levels of the stress-linked hormone cortisol (C), but findings are inconsistent, probably reflecting methodological weaknesses especially in taking account of C's diurnal cycle.
  
  
  METHODS
  High and low N students [Total N=118; mean age=20.99years] were recruited and their salivary cortisol measured, ensuring that saliva samples were numerically adequate to assess C's diurnal cycle over two days with objective verification of sample timing.
  
  
  RESULTS
  Cortisol secretion was approximately 20% higher in High N than low N participants in the period of 12h after awakening (p<.008), but no differences in secretion were evident during the first 0.75 of this period, when typically the Cortisol Awakening Response (CAR) rapidly takes cortisol to its daily peak. N effects were thus confined to the 0.75h-12h period (p<.007). Males had approximately 25% higher cortisol secretion levels than females, also confined to the 0.75h-12h period (p<.003). No significant differences between N groups were evident for dynamic measures of cortisol change, viz. the magnitude of CAR rise and subsequent diurnal fall. All effects were controlled for cohort date of study entry, age, smoking status, study day and time of awakening.
  
  
  CONCLUSIONS
  With careful control, it appears that an important theoretically predicted effect exists, and is replicated in different student intake cohorts recruited in different years. Most importantly, findings support several lines of evidence that the period of massive rise in the brief 0-0.75h CAR period should be seen as quite separate from the rest of the diurnal cycle, underpinned by different control mechanisms, and with potentially different correlates.
authors.affiliation: Research Institute on Health Sciences (IUNICS), University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Majorca, Spain. Electronic address: ggbanda@uib.es.
authors.forename: Gloria
authors.initials: G
authors.lastname: Garcia-Banda
authors.affiliation: Department of Psychology, University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Majorca, Spain.
authors.forename: Karin
authors.initials: K
authors.lastname: Chellew
authors.affiliation: Department of Nursing and Physiotherapy, University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Majorca, Spain.
authors.forename: Joana
authors.initials: J
authors.lastname: Fornes
authors.affiliation: Clinical Analysis Laboratory, Son Espases University Hospital, Ctra. de Valldemossa, 79, 07120 Palma de Majorca, Spain.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Perez
authors.affiliation: Research Institute of Health Sciences (IUNICS), University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Majorca, Spain.
authors.forename: Mateu
authors.initials: M
authors.lastname: Servera
authors.affiliation: Psychophysiology and Stress Research Group, University of Westminster, 309 Regent Street, London W1B 2UW, UK.
authors.forename: Phil
authors.initials: P
authors.lastname: Evans
mesh_terms: D000328:Adult; D001008:Anxiety Disorders / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D008297:Male; D000075384:Neuroticism; D010551:Personality / Q000502:physiology*; D012463:Saliva / Q000737:chemistry; D012737:Sex Factors; D055815:Young Adult
chemical_list: D006854:Hydrocortisone
keywords: CAR; Diurnal cycle; Neuroticism; Personality; Salivary cortisol