title: The direction of longitudinal associations between sleep problems and depression symptoms: a study of twins aged 8 and 10 years.
abstract: OBJECTIVE
  To establish the direction and etiology of longitudinal associations between sleep problems and depression symptoms in children.
  
  
  METHODS
  Data on twins aged 8 and 10 years were obtained. At assessments, parents completed the Child Sleep Habits Questionnaire, and twins completed the Children's Depression Inventory.
  
  
  METHODS
  Participants were mainly interviewed at the Institute of Psychiatry, London.
  
  
  METHODS
  Three hundred twin pairs initially enrolled in the study.
  
  
  METHODS
  N/A.
  
  
  RESULTS
  A genetically informative cross-lagged model examined links between sleep and depression. Sleep problems at age 8 predicted depression at age 10 (partial regression coefficient [95% confidence intervals] = 0.10 [0.01-0.18]). The converse was not found. Stability of sleep problems across time was mainly due to genes (46% of the genetic influence on sleep at 10 was due to the same genetic influence on sleep aged 8). Stability of depression was mainly due to non-shared environmental influences (19% of the nonshared environmental influence on depression at 10 was due to the same nonshared environmental influence on depression at age 8). The cross-lagged association between sleep problems at 8 and depression at 10 years was largely due to genes, although this finding was nonsignificant.
  
  
  CONCLUSIONS
  This study adds to our understanding of the temporal precedence of sleep problems and depression and the risks underlying their associations. There are implications regarding the value of specifying genes linked to sleep problems and potential opportunities for informing early intervention strategies in high-risk groups at key points in the progression to developing more serious problems.
authors.affiliation: Department ofPsychology, Goldsmiths College, University ofLondon, London, UK; I2lnstitute ofPsychiatry, King's College London, London, UK. a.gregory@gold.ac.uk
authors.forename: Alice M
authors.initials: AM
authors.lastname: Gregory
authors.forename: Frühling V
authors.initials: FV
authors.lastname: Rijsdijk
authors.forename: Jennifer Y F
authors.initials: JY
authors.lastname: Lau
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Dahl
authors.forename: Thalia C
authors.initials: TC
authors.lastname: Eley
mesh_terms: D001007:Anxiety / Q000175:diagnosis / Q000235:genetics; D002648:Child; D003863:Depression / Q000175:diagnosis / Q000235:genetics*; D004200:Diseases in Twins / Q000175:diagnosis / Q000235:genetics*; D004739:England; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015233:Models, Statistical; D010641:Phenotype; D012307:Risk Factors; D012893:Sleep Wake Disorders / Q000175:diagnosis / Q000235:genetics*; D012931:Social Environment; D014852:Wales