Psychological Medicine



Original Article

A twin study of genetic and environmental influences on suicidality in men


Q.  FU  c1 a1, A. C.  HEATH  a1, K. K.  BUCHOLZ  a1, E. C.  NELSON  a1, A. L.  GLOWINSKI  a1, J.  GOLDBERG  a1, M. J.  LYONS  a1, M. T.  TSUANG  a1, T.  JACOB  a1, M. R.  TRUE  a1 and S. A.  EISEN  a1
a1 From the Missouri Alcoholism Research Center at Washington University, Department of Psychiatry and Department of Internal Medicine, Washington University School of Medicine, Research and Medical Service, St. Louis VAMC and Missouri Alcoholism Research Center at St. Louis University, St. Louis University School of Public Health, St. Louis, Missouri; Department of Veterans Affairs, VET Registry/Seattle ERIC and Department of Epidemiology, University of Washington School of Public Health, Seattle, Washington; Department of Psychology, Boston University, Harvard Medical School Department of Psychiatry at the Brockton/West Roxbury VA, Brockton, Harvard Institute of Psychiatric Epidemiology and Genetics, Harvard Medical School Department of Psychiatry at Massachusetts Mental Health Center and Department of Epidemiology and Menlo Park VA Hospital, Menlo Park, California, USA

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.


Correspondence:
c1 Address for correspondence: Dr Qiang Fu, Missouri Alcoholism Research Center, Department of Psychiatry, Washington University, School of Medicine, 40N Kingshighway Blvd., Suite 2, St. Louis, Missouri 63108, USA.


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