title: A Longitudinal Twin and Sibling Study of Associations between Insomnia and Depression Symptoms in Young Adults.
abstract: To estimate genetic and environmental influences on the associations between insomnia and depression symptoms concurrently and longitudinally.
  
  
  
  Behavioral genetic analyses were conducted on data from the British longitudinal G1219 twin/sibling study. One thousand five hundred fiftysix twins and siblings participated at Time 1 (mean age = 20.3 years, SD = 1.76). Eight hundred sixty-two participated at Time 2 (mean age = 25.2 years, SD = 1.73 years). Participants completed the Insomnia Symptoms Questionnaire and the Short Mood and Feelings Questionnaire to assess symptoms of insomnia and depression respectively.
  
  
  
  Genetic effects accounted for 33% to 41% of the variance of the phenotypes. The phenotypic correlations were moderate (r = 0.34 to r = 0.52). The genetic correlations between the variables were high (0.73-1.00). Genetic effects accounted for a substantial proportion of the associations between variables (50% to 90%). Non-shared environmental effects explained the rest of the variance and covariance of the traits.
  
  
  
  While genetic effects play a modest role in insomnia and depression symptoms separately, they appear to play a more central role in concurrent and longitudinal associations between these phenotypes. This should be acknowledged in theories explaining these common associations.
authors.affiliation: Department of Psychology, Goldsmiths, University of London, London, UK.
authors.forename: Alice M
authors.initials: AM
authors.lastname: Gregory
authors.affiliation: MRC Social, Genetic & Developmental Psychiatry Centre, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London UK.
authors.forename: Fruhling V
authors.initials: FV
authors.lastname: Rijsdijk
authors.affiliation: MRC Social, Genetic & Developmental Psychiatry Centre, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London UK.
authors.forename: Thalia C
authors.initials: TC
authors.lastname: Eley
authors.affiliation: Department of Psychiatry, School of Medicine, University of Pittsburgh.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Buysse
authors.affiliation: Department of Psychology, Goldsmiths, University of London, London, UK.
authors.forename: Melanie N
authors.initials: MN
authors.lastname: Schneider
authors.affiliation: MRC Harwell, UK.
authors.forename: Mike
authors.initials: M
authors.lastname: Parsons
authors.affiliation: Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, Sir William Dunn School of Pathology, University of Oxford, UK.
authors.forename: Nicola L
authors.initials: NL
authors.lastname: Barclay
mesh_terms: D000293:Adolescent; D000328:Adult; D003863:Depression / Q000175:diagnosis / Q000209:etiology* / Q000235:genetics; D004200:Diseases in Twins / Q000175:diagnosis / Q000209:etiology* / Q000235:genetics / Q000523:psychology; D004777:Environment; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010641:Phenotype; D011569:Psychiatric Status Rating Scales; D012307:Risk Factors; D035781:Siblings; D007319:Sleep Initiation and Maintenance Disorders / Q000175:diagnosis / Q000209:etiology* / Q000235:genetics / Q000523:psychology; D011795:Surveys and Questionnaires; D014427:Twins / Q000235:genetics; D055815:Young Adult
keywords: depression; genetics; insomnia; longitudinal; twins