Qiang Fu¹, Andrew C. Heath², Kathleen K. Bucholz², William R. True¹, and Seth A. Eisen³. (1) Department of Community Health, Saint Louis University School of Public Health, Salus Center, 3545 Lafayette Ave., Suite 300, St. Louis, MO 63104, (314)977-8134, qjfu@slu.edu, (2) Department of Psychiatry, Washington University School of Medicine, 40 N. Kingshighway Blvd., Suite 1, St. Louis, MO 63108, (3) Department of Internal Medicine, Washington University School of Medicine, 40 N. Kingshighway Blvd., Suite 1, St. Louis, MO 63108

Epidemiological studies have reported that smoking is associated with increased risk for suicidality. However, the mechanism of the relationship is poorly understood. A common flaw of existing studies is lack of comprehensive control for genetic and environmental risk factors for both variables. This study was aimed to examine whether nicotine dependence and suicidality shared common genetic and environmental risk factors. Data from 6,479 middle-aged male-male monozygotic and dizygotic twin members of the Vietnam Era Twin Registry were analyzed using structural equation modeling. We estimated genetic, shared environmental and nonshared environmental variances for lifetime suicidality (suicidal ideation or suicide attempts) and lifetime DSM3R nicotine dependence as well as to corresponding genetic, shared environmental and nonshared environmental correlations that assess the degree of overlap of genetic or environmental risk factors for the two variables. The genetic correlation between liabilities to nicotine dependence and suicidality was 0.38 (0.29-0.48); the nonshared environmental correlation was 0.16 (0.05-0.26). The genetic correlation explained 74.1% of the phenotypic correlation. After controlling for sociodemographic and psychiatric predictors for suicidality, the genetic correlation between liabilities to nicotine dependence and suicidality was reduced to 0.11 (0.002-0.25); the nonshared environmental correlation was 0.08 (0.00-0.19). The genetic correlation explained 51.4% of the phenotypic correlation. Our data suggest that the association between nicotine dependence and suicidality is largely explained by genetic risk factors associated with other major psychiatric risk factors. We cannot rule out a genetic correlation of nicotine dependence and suicidality after controlling for other major psychiatric risk factors.

Learning Objectives:

• The participants should recognize that genetic risk factors play an important role on the association between nicotine dependence and suicidality, and better understand how genetic and environmental risk factors for other psychiatric risk factors related to both nicotine dependence and suicidality underlie this association.

Keywords: Tobacco, Suicide

Presenting author's disclosure statement:
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.