title: Associations between diurnal preference, sleep quality and externalizing behaviours: a behavioural genetic analysis.
abstract: BACKGROUND
  Certain aspects of sleep co-occur with externalizing behaviours in youth, yet little is known about these associations in adults. The present study: (1) examines the associations between diurnal preference (morningness versus eveningness), sleep quality and externalizing behaviours; (2) explores the extent to which genetic and environmental influences are shared between or are unique to these phenotypes; (3) examines the extent to which genetic and environmental influences account for these associations. method: Questionnaires assessing diurnal preference, sleep quality and externalizing behaviours were completed by 1556 young adult twins and siblings.
  
  
  RESULTS
  A preference for eveningness and poor sleep quality were associated with greater externalizing symptoms [r=0.28 (95% CI 0.23-0.33) and 0.34 (95% CI 0.28-0.39), respectively]. A total of 18% of the genetic influences on externalizing behaviours were shared with diurnal preference and sleep quality and an additional 14% were shared with sleep quality alone. Non-shared environmental influences common to the phenotypes were small (2%). The association between diurnal preference and externalizing behaviours was mostly explained by genetic influences [additive genetic influence (A)=80% (95% CI 0.56-1.01)], as was the association between sleep quality and externalizing behaviours [A=81% (95% CI 0.62-0.99)]. Non-shared environmental (E) influences accounted for the remaining variance for both associations [E=20% (95% CI -0.01 to 0.44) and 19% (95% CI 0.01-0.38), respectively].
  
  
  CONCLUSIONS
  A preference for eveningness and poor sleep quality are moderately associated with externalizing behaviours in young adults. There is a moderate amount of shared genetic influences between the phenotypes and genetic influences account for a large proportion of the association between sleep and externalizing behaviours. Further research could focus on identifying specific genetic polymorphisms common to both sleep and externalizing behaviours.
authors.affiliation: Department of Psychology, Goldsmiths, University of London, Lewisham Way, New Cross, London, UK. ps701nh@gold.ac.uk
authors.forename: N L
authors.initials: NL
authors.lastname: Barclay
authors.forename: T C
authors.initials: TC
authors.lastname: Eley
authors.forename: B
authors.initials: B
authors.lastname: Maughan
authors.forename: R
authors.initials: R
authors.lastname: Rowe
authors.forename: A M
authors.initials: AM
authors.lastname: Gregory
mesh_terms: D000293:Adolescent; D000328:Adult; D002940:Circadian Rhythm; D015897:Comorbidity; D003430:Cross-Sectional Studies; D004739:England / Q000453:epidemiology; D004777:Environment; D005260:Female; D005824:Genetics, Behavioral; D006801:Humans; D008297:Male; D008957:Models, Genetic; D015999:Multivariate Analysis; D010641:Phenotype; D035781:Siblings; D012890:Sleep / Q000235:genetics; D012893:Sleep Wake Disorders / Q000453:epidemiology* / Q000235:genetics*; D012920:Social Behavior Disorders / Q000453:epidemiology* / Q000235:genetics*; D055815:Young Adult