title: A twin study of genetic and environmental influences on suicidality in men.
abstract: BACKGROUND
  Previous studies that have examined genetic influences on suicidal behaviour were confounded by genetic vulnerability for psychiatric risk factors. The present study examines genetic influences on suicidality (i.e. suicidal ideation and/or suicide attempt) after controlling for the inheritance of psychiatric disorders.
  
  
  METHODS
  Sociodemographics, combat exposure, lifetime DSM-III-R major depression, bipolar disorder, childhood conduct disorder, adult antisocial personality disorder, panic disorder, post-traumatic stress disorder, drug dependence, alcohol dependence and lifetime suicidal ideation and attempt were assessed in 3372 twin pairs from the Vietnam Era Twin Registry who were assessed in 1987 and 1992. Genetic risk factors for suicidality were examined in a multinomial logistic regression model. Additive genetic, shared environmental and non-shared environmental effects on suicidality were estimated using structural equation modelling, controlling for other risk factors.
  
  
  RESULTS
  The prevalence of suicidal ideation and suicide attempt were 16.1% and 2.4% respectively. In a multinomial regression model, co-twin's suicidality, being white, unemployment, being other than married, medium combat exposure and psychiatric disorders were significant predictors for suicidal ideation. Co-twin's suicidality, unemployment, marital disruption, low education attainment and psychiatric disorders (except childhood conduct disorder) were significant predictors for suicide attempt. Model-fitting suggested that suicidal ideation was influenced by additive genetic (36%) and non-shared environmental (64%) effects, while suicide attempt was affected by additive genetic (17%), shared environmental (19%) and non-shared environmental (64%) effects.
  
  
  CONCLUSIONS
  There may be a genetic susceptibility specific to both suicidal ideation and suicide attempt in men, which is not explained by the inheritance of common psychiatric disorders.
authors.affiliation: Missouri Alcoholism Research Center at Washington University, Department of Psychiatry and Washington University School of Medicine, St Louis, Missouri 63108, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Fu
authors.forename: A C
authors.initials: AC
authors.lastname: Heath
authors.forename: K K
authors.initials: KK
authors.lastname: Bucholz
authors.forename: E C
authors.initials: EC
authors.lastname: Nelson
authors.forename: A L
authors.initials: AL
authors.lastname: Glowinski
authors.forename: J
authors.initials: J
authors.lastname: Goldberg
authors.forename: M J
authors.initials: MJ
authors.lastname: Lyons
authors.forename: M T
authors.initials: MT
authors.lastname: Tsuang
authors.forename: T
authors.initials: T
authors.lastname: Jacob
authors.forename: M R
authors.initials: MR
authors.lastname: True
authors.forename: S A
authors.initials: SA
authors.lastname: Eisen
mesh_terms: D000328:Adult; D004200:Diseases in Twins / Q000235:genetics*; D020022:Genetic Predisposition to Disease / Q000523:psychology; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D012931:Social Environment; D013406:Suicide, Attempted / Q000523:psychology* / Q000706:statistics & numerical data