Disruptive behaviors (i.e., symptoms of conduct and oppositional defiant disorder) are a risk factor for suicidal behavior, although few behavior genetics studies have investigated this association. This study aimed to... [ view full abstract ]
Disruptive behaviors (i.e., symptoms of conduct and oppositional defiant disorder) are a risk factor for suicidal behavior, although few behavior genetics studies have investigated this association. This study aimed to examine: 1) the genetic and environmental contributions to adolescent suicide attempt/self-harm (SA/SH) and 2) the association between childhood disruptive behaviors childhood and adolescent SA/SH.
We analyzed data from the Child and Adolescent Twin Study of Sweden, a population-based study of twins (i.e., 29,000 twins at age 9 and 9,000 twins through age 18) born in Sweden from 1992-2007. When twins were 9, their parents completed the Autism – Tics, AD/HD and other Comorbidities Inventory, which indexed oppositional/conduct symptoms. When twins were 18, they completed the Lifetime History of Aggression questionnaire and the Brief Obsessive-Compulsive Survey, which indexed self-harm and suicide attempts. We also included inpatient/outpatient suicide attempts via ICD-10 codes from the National Patient Register.
We conducted a confirmatory factor analysis of four SA/SH items. All items loaded onto a single factor, which was moderately heritable (h2 = 0.68, 95% CI [0.21-1.14]) with the remaining variance attributable to nonshared environmental factors. We also conducted population-wide and within-twin-pair logistic regression models to assess the association between disruptive behaviors and SA/SH. Every one increase in disruptive behaviors symptoms was associated with SA/SH in the population (OR = 1.06 [1.03-1.09]). The magnitude of the association remained in within-twin-pair analyses (OR=1.08 [0.99-1.19]), and there were no differences between identical and fraternal twins. We found comparable results using diagnostic cutoffs.
This study demonstrated two major findings: 1) the self-harm and suicide attempt items loaded onto a single factor, which was moderately heritable, and 2) genetic and shared environmental factors did not appear to confound the association between disruptive behaviors and SA/SH. This is the first study to examine the etiology of adolescent suicidality using behavior genetics.
