Heritability of suicide attempt stronger among young people, women

A partial overlap exists in the genetic and environmental aetiologies of suicide attempt and death, which also exhibit modest sex differences and shift across the course of life, a study has shown.

The authors used the Swedish national registry data to identify a large cohort of twins, full siblings, and half siblings (n=1,314,990) born between 1960 and 1990 and followed until 2015. They estimated heritability for suicide attempt and suicide death by conducting a twin-family modeling of these outcomes, along with genetic and environmental correlations between them. Finally, the association between suicide attempt by young people and adults was assessed.

Bivariate models showed that suicide attempt and death were moderately heritable among both women (attempt: additive genetic variance component [A], 0.52, 95 percent confidence interval [CI], 0.44–0.56; death: A, 0.45, 95 percent CI, 0.39–0.59) and men (attempt: A, 0.41, 95 percent CI, 0.38–0.49; death: A, 0.44, 95 percent CI, 0.43–0.44).

Outcomes were significantly, but incompletely, associated genetically (women: rA, 0.67, 95 percent CI, 0.55–0.67; men: rA, 0.74, 95 percent CI, 0.63–0.87), while environmental correlations were weaker (women: rE, 0.36, 95 percent CI, 0.29–0.45; men: rE, 0.21, 95 percent CI, 0.19–0.27).

Heritability of suicide attempt was stronger among younger people (aged 10–24 years; A, 0.55–0.62) than adults (aged ≥25 years; A, 0.36–0.38). The genetic association between attempt during youth and adulthood was more robust for women (rA, 0.79, 95 percent CI, 0.72–0.79) than for men (rA, 0.39, 95 percent CI, 0.26–0.47).

“These differences must be considered when developing prevention efforts and risk prediction algorithms,” the authors said. “Where feasible, suicide attempt and death should be considered separately rather than collapsed, including in the context of gene identification efforts.”