title: Genetic and familial environmental effects on suicide attempts: a study of Danish adoptees and their biological and adoptive siblings.
abstract: OBJECTIVE
  Genetic factors have been found to influence the risk of suicide. It is less clear if this also applies to attempted suicide. We have investigated genetic and familial environmental factors by studying the occurrence of suicide attempts in biological and adoptive siblings of adoptees who attempted suicide compared to siblings of adoptees with no suicide attempts.
  
  
  METHODS
  We used a random sample of 1933 adoptees from the Danish Adoption Register, a register of non-familial adoptions of Danish children, i.e. the adoptive parents are biologically unrelated to the adoptee. Analyses were conducted on incidence rates of attempted suicide in biological and adoptive siblings given occurrence of attempted suicide in the adoptees while also taking into account psychiatric disorders. Information about suicidal attempt and history of psychiatric disorder was based on hospital admissions.
  
  
  RESULTS
  The rate of attempted suicide in full siblings of adoptees who attempted suicide before age 60 years was higher than in full siblings of adoptees who had not attempted suicide (incidence rate ratios (IRR)=3.45; 95% confidence interval [CI]=0.94-12.7). After adjustment for history of psychiatric admission of siblings the increased rate was statistically significant (IRR=3.88; 95% CI-1.42-10.6).
  
  
  CONCLUSIONS
  Information on attempted suicide and psychiatric history was limited to that which involved hospitalisation.
  
  
  CONCLUSIONS
  Genetic factors influence risk of suicide attempts.
authors.affiliation: Institute of Preventive Medicine, Bispebjerg and Frederiksberg Hospital, Capital Region, Copenhagen, Denmark; National Centre for Register-based Research, Fuglesangs Allé 4, Aarhus University, DK-8210 Aarhus V, Denmark. Electronic address: LLP@ncrr.dk.
authors.forename: Liselotte
authors.initials: L
authors.lastname: Petersen
authors.affiliation: Institute of Preventive Medicine, Bispebjerg and Frederiksberg Hospital, Capital Region, Copenhagen, Denmark; Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Thorkild I A
authors.initials: TI
authors.lastname: Sørensen
authors.affiliation: Department of Biostatistics, University of Copenhagen, Øster Farimagsgade 5B, DK-1014 Copenhagen K, Denmark.
authors.forename: Per
authors.initials: P
authors.lastname: Kragh Andersen
authors.affiliation: National Centre for Register-based Research, Fuglesangs Allé 4, Aarhus University, DK-8210 Aarhus V, Denmark.
authors.forename: Preben Bo
authors.initials: PB
authors.lastname: Mortensen
authors.affiliation: Centre for Suicide Research, University Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, UK.
authors.forename: Keith
authors.initials: K
authors.lastname: Hawton
mesh_terms: D000300:Adoption / Q000523:psychology*; D002648:Child; D015331:Cohort Studies; D003718:Denmark; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D008297:Male; D008875:Middle Aged; D012042:Registries; D012307:Risk Factors; D035781:Siblings / Q000523:psychology*; D013406:Suicide, Attempted / Q000706:statistics & numerical data*
keywords: Adoption study; Familial environment; Genetics; Siblings; Suicide attempts