title: Personality differences in patients with delayed sleep-wake phase disorder and non-24-h sleep-wake rhythm disorder relative to healthy sleepers.
abstract: Delayed sleep-wake phase disorder (DSWPD) is associated with a delayed timing of circadian rhythms, and this delay is suggested to be the basis of the disorder. However, this has been questioned due to frequent relapses following treatment based on this aetiology. Recent studies have emerged suggesting personality factors may contribute to sleep patterns in DSWPD. The aim of this study was to further investigate circadian and personality factors in DSWPD patients as well as patients with non-24-h sleep-wake rhythm disorder (N24SWD) relative to control sleepers.
  
  
  
  This sample consisted of 16 DSWPD (age = 21.1 ± 2.8, 10 m, 7 f), and three N24SWD patients (age = 24.0 ± 4.4, 2 m, 1 f). Controls were seven males and seven females (age = 23.4 ± 5.9). Before starting an 80-h modified constant routine, eligible participants' sleep patterns were monitored for a week and they completed a personality questionnaire (NEO PI-R). An ultradian routine with alternating 20-min sleep opportunities and 40 min of enforced wakefulness was used to measure the timing of endogenous circadian temperature and melatonin rhythms.
  
  
  
  As compared with controls, DSWPD patients reported higher neuroticism, significantly lower extraversion, conscientiousness and agreeableness. Similarly, N24SWD patients' patterns of personality traits were similar to that of DSWPD. Conscientiousness, in particular, was associated with phase timings of circadian rhythms as well as sleep measures and lifestyle factors within the DSWPD group.
  
  
  
  These findings suggest that circadian rhythm sleep-wake disorders (CRSWDs) may not only stem from circadian abnormalities but personality factors may also drive lifestyle choices, including sleep timing.
authors.affiliation: School of Psychology, Flinders University of South Australia, Adelaide, SA, Australia. Electronic address: gorica.micic@flinders.edu.au.
authors.forename: Gorica
authors.initials: G
authors.lastname: Micic
authors.affiliation: Adelaide Institute for Sleep Health: A Flinders Centre of Research Excellence, School of Medicine, Faculty of Medicine, Nursing and Health Sciences, Flinders University, Bedford Park, South Australia, Australia.
authors.forename: Nicole
authors.initials: N
authors.lastname: Lovato
authors.affiliation: School of Psychology, Flinders University of South Australia, Adelaide, SA, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Gradisar
authors.affiliation: School of Psychology, Flinders University of South Australia, Adelaide, SA, Australia; Adelaide Institute for Sleep Health: A Flinders Centre of Research Excellence, School of Medicine, Faculty of Medicine, Nursing and Health Sciences, Flinders University, Bedford Park, South Australia, Australia.
authors.forename: Leon C
authors.initials: LC
authors.lastname: Lack
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D010551:Personality; D010554:Personality Disorders / Q000150:complications; D020178:Sleep Disorders, Circadian Rhythm / Q000523:psychology*; D055815:Young Adult
keywords: Circadian rhythm sleep–wake disorders; Delayed sleep; Entrainment; Light cues; Zeitgebers