title: Sleep terrors in children: a prospective study of twins.
abstract: OBJECTIVE
  There is growing evidence that genetic factors are involved in the occurrence of sleep terrors. Twin studies provide invaluable information regarding genetic and environmental factors that can affect the manifestation of the disease; however, most previous twin studies on sleep terrors were performed retrospectively or with a sample that was too small to yield conclusive results. The aim of this large prospective study was to clarify the genetic and environmental contributions to sleep terrors in childhood.
  
  
  METHODS
  In all, 390 pairs of monozygotic and dizygotic twins were recruited at birth for a longitudinal study. The prevalence and frequency of sleep terrors were assessed at 18 and 30 months of age with a questionnaire administered to the biological mother of the twins. Zygosity was determined by a questionnaire and genotyping. The prevalence and polychoric correlation for each type of twins were calculated. Structural-equation modeling was used to determine the proportion of variance attributable to additive genetic, shared, and nonshared environmental factors.
  
  
  RESULTS
  The prevalence of sleep terrors was 36.9% at 18 months and 19.7% at 30 months; 49% of affected children were boys, and 51% were girls. At 18 months, the polychoric correlations were 0.63 for monozygotic and 0.36 for the dizygotic twins. These were 0.68 (monozygotic) and 0.24 (dizygotic) at 30 months. Our model-fitting analysis showed that sleep terrors were explained by a 2-component model at 18 months (43.7% additive genetic effects and 56.3% nonshared environment) and at 30 months (41.5% additive genetic effects and 58.5% nonshared environment).
  
  
  CONCLUSIONS
  These results strongly support the heritability of sleep terrors. There also seems to be continuity in genetic effects with the persistence of sleep-terror symptoms.
authors.affiliation: Sleep Disorders Center, Sacre-Coeur Hospital, 5400 Gouin Blvd W, Montreal, Quebec, Canada H4J 1C5.
authors.forename: Bich Hong
authors.initials: BH
authors.lastname: Nguyen
authors.forename: Daniel
authors.initials: D
authors.lastname: Pérusse
authors.forename: Jean
authors.initials: J
authors.lastname: Paquet
authors.forename: Dominique
authors.initials: D
authors.lastname: Petit
authors.forename: Michel
authors.initials: M
authors.lastname: Boivin
authors.forename: Richard E
authors.initials: RE
authors.lastname: Tremblay
authors.forename: Jacques
authors.initials: J
authors.lastname: Montplaisir
mesh_terms: D017677:Age Distribution; D002675:Child, Preschool; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D020184:Night Terrors / Q000453:epidemiology* / Q000235:genetics*; D015995:Prevalence; D011446:Prospective Studies; D011792:Quebec; D018570:Risk Assessment; D017678:Sex Distribution; D014427:Twins / Q000235:genetics*; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic