Does shared genetic risk contribute to the co-occurrence of eating disorders and suicidality?
OBJECTIVE
There is a high level of co-occurrence of suicidality with eating disorders (EDs) but the reason for this is unknown. To test the hypothesis that suicidality and EDs share genetic risk contributing to the expression of both phenotypes.


METHOD
Female twins (N = 1,002) from the Australian Twin Registry, aged 28-40 years, were interviewed with diagnostic interviews. Lifetime diagnostic information relating to eating disorders [anorexia nervosa (AN), bulimia nervosa (BN), binge eating disorder, and purging disorder (PD)], suicidality (ranging transitory thoughts to suicide attempts), and major depression.


RESULTS
Any suicidal thoughts were reported by 24% of the sample, but prevalence of lifetime suicidality among female twins with EDs was much higher (43%), presence of an ED diagnosis more than doubling likelihood of suicidality (OR = 2.32, 95% CI: 1.63-3.31). AN and BN conveyed greatest risk of suicidality (OR = 2.03, 95% CI: 1.06-3.87; OR = 3.97, 95% CI: 2.01-7.85, respectively). Twin phenotype correlations showed monozygotic twins had uniformly higher estimates than dizygotic counterparts. A trivariate Cholesky model indicated a common genetic influence on suicidality and ED phenotypes (but not depression), and no nonshared environmental source.


DISCUSSION
Both cross twin phenotypic correlations and genetic modeling infer a common genetic pathway for suicidality and EDs, but further investigation is needed to elucidate whether this may constitute emotional dysregulation or other temperament-linked factors. Study findings also indicate that ED clients must be routinely assessed for presence of suicidality, independent of depression status.