title: Too Long, Too Short, or Too Variable? Sleep Intraindividual Variability and Its Associations With Perceived Sleep Quality and Mood in Adolescents During Naturalistically Unconstrained Sleep.
abstract: Research has extensively examined the relationship between adolescents' mental health and average sleep duration/quality. Using rigorous methodology, this study characterized adolescents' objective sleep intraindividual variability (IIV) and examined its role on mood beyond the effects of their respective individual mean (IIM) values.
  
  
  
  One hundred forty-six community-dwelling adolescents (47.3% male) aged 16.2 ± 1.0 (M ± SD) years wore an actigraph that assessed bedtime, risetime, time-in-bed (TIB), and sleep onset latency (SOL) throughout a 15-day vacation with relatively unconstrained sleep opportunity. Self-report sleep quality (SSQ), negative mood (MOOD), and other covariates were assessed using questionnaires. For each sleep variable, individuals' mean values (IIM) and IIV were used to simultaneously predict MOOD with SSQ as a mediator. Models were estimated in a Bayesian IIV framework; both linear and quadratic effects of the IIM and IIV were examined.
  
  
  
  Longer and more variable TIB, as well as more variable SOL (but not mean SOL), were associated with poorer SSQ (ps < .01), which in turn, was associated with more negative MOOD (ps < .05). The indirect effect of SOL IIV was curvilinear, such that as SOL became more variable, the deteriorating effect of high SOL IIV accelerated. Neither bedtime nor risetime IIV was significantly associated with SSQ or MOOD.
  
  
  
  During relatively unconstrained sleep opportunity, more variable TIB and SOL were associated with more negative mood, mediated by poorer perceived sleep quality. Significant effects of IIV were over and above that of mean values, suggesting that unique aspects of sleep IIV are relevant to how adolescents perceive sleep quality and their mood.
authors.affiliation: Monash Institute of Cognitive and Clinical Neurosciences, School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, Victoria, Australia.|Centre for Women's Mental Health, Department of Psychiatry, University of Melbourne, Royal Women's Hospital, Parkville, Victoria, Australia.
authors.forename: Bei
authors.initials: B
authors.lastname: Bei
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Stanford University, Palo Alto, CA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Manber
authors.affiliation: Department of Psychology, University of Oregon, Eugene, OR.|Melbourne School of Psychological Sciences, University of Melbourne, Victoria, Australia.
authors.forename: Nicholas B
authors.initials: NB
authors.lastname: Allen
authors.affiliation: Melbourne School of Psychological Sciences, University of Melbourne, Victoria, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Trinder
authors.affiliation: Monash Institute of Cognitive and Clinical Neurosciences, School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, Victoria, Australia.
authors.forename: Joshua F
authors.initials: JF
authors.lastname: Wiley
mesh_terms: D000293:Adolescent; D000339:Affect; D001499:Bayes Theorem; D005260:Female; D006801:Humans; D007206:Individuality; D008297:Male; D057566:Self Report; D012890:Sleep / Q000502:physiology*; D007319:Sleep Initiation and Maintenance Disorders / Q000523:psychology; D011795:Surveys and Questionnaires; D013997:Time Factors
keywords: adolescents; anxiety; depression; intraindividual variability; mood; sleep; sleep restriction; vacation.