Genetic Liability Differences Exist in Suicide, Undetermined Intent Decedents

A phenotype-based genetic analysis found only small differences in liabilities between decedents of unambiguous suicide and undetermined intent (UDI) deaths, according to study findings published in Suicide and Life-Threatening Behavior.

Researchers sourced data for this study from population-based registers in Sweden. Individuals (N=42,458) aged 15 years and older who died by suicide (n=31,835) or UDI (n=10,623) between 1969 and 2018 were evaluated for family genetic risk scores (FGRS) for major depression (MD), anxiety disorders, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder (ADHD), bipolar disorder (BD), schizophrenia, bulimia, anorexia nervosa, alcohol use disorder (AUD), drug use disorder (DUD), criminal behavior, suicide death, and suicide attempt.

Among decedents, 30,421 were men or boys and 12,037 were women or girls. The average age for suicide deaths was 42.9 years and for UDI deaths was 42.7 years. The proportion of UDI deaths ranged from 15.5% for individuals aged 75 years and older to 27.3% for those aged 35 to 44 years.

In the fully adjusted model that included sociodemographic characteristics, 8 of the FGRS outcomes, and phenotypes associated with all of the FGRS outcomes, patients with elevated FGRS for MD (adjusted odds ratio [aOR], 0.92; 95% CI, 0.90-0.95) and suicide death (aOR, 0.96; 95% CI, 0.94-0.97) were at decreased risk for death by UDI. Those with higher FGRS for AUD (aOR, 1.03; 95% CI, 1.01-1.05), ADHD (aOR, 1.03; 95% CI, 1.01-1.05), and criminal behavior (aOR, 1.03; 95% CI, 1.01-1.06) were at increased risk for death by UDI.

According to the phenotypic register, individuals with MD (aOR, 0.52; 95% CI, 0.49-0.55) and BD (aOR, 0.72; 95% CI, 0.64-0.81) were less likely to die by UDI. Those with AUD (aOR, 5.12; 95% CI, 4.85-5.40), DUD (aOR, 2.13; 95% CI, 2.00-2.27), and criminal behavior (aOR, 1.30; 95% CI, 1.22-1.38) were more likely to die by UDI.

The findings of this study may be limited by the FGRS, which is conceptually related to polygenic risk scores, but does not rely on genetic factors and instead is based on familial phenotypes.

Study authors conclude, “We found, using Swedish national medical and criminal registries, minor differences in genetic liability across individuals who died by suicide vs those whose deaths were classified as being of undetermined intent. Specifically, the latter exhibited higher genetic liability to substance use disorders, criminal behavior, and ADHD, and lower genetic liability to depression and suicide.”