Suicide is a major global public health concern, with nearly 700,000 deaths annually and an age-standardized rate of about 9 per 10,000 people. Suicide attempts are even more common, which affects an estimated 2.7 to 3.3% of people during their lifetime, and a previous attempt strongly predicts future suicide. Understanding the determinants of suicide attempts is therefore important to prevent and monitor global health targets, including the United Nations Sustainable Development Goals.
Suicidal behaviour shows clear sex differences: males account for most suicide deaths, whereas females report roughly twice as many attempts. These disparities are likely due to complex biopsychosocial factors such as social norms, neurobiological differences, environmental risks, and hormonal influences. However, evidence on sex differences in genetic risk remains mixed. A recent study published in BMJ Mental Health used Swedish population registers to examine the genetic contributions to suicide attempts and their sex-specific patterns.
This Swedish population-based cohort study used data from several national registers, such as the National Patient Register, the cause of death register, the multi-generation register, the total population register, and the Swedish Medical Birth Register. A total of 3,058,374 individuals (female = 48.6%, mean age = 39.6±10.5 years at the end of the follow-up period) born from 1963 to 1998 who were alive and residing in Sweden at age 10 years were included. All the participants were followed between the ages of 10 years and December 31, 2019. Siblings and parents were also included in this study to examine the familial patterns. Statistical analyses assessed heritability, familial aggregation, familial coaggregation, and genetic correlations by using structural equation models and generalized estimating equations. Sensitivity analyses evaluated the time to event models, age differences, and immigrant inclusion.
Approximately 2.9% of the population (n = 89,278) had at least one suicide attempt (female = 55%), whereas 4.1% (n = 126,411) reported self-harm (female = 50%). Suicide attempts were more serious in females compared to males (3.3% vs 2.6%). Psychiatric disorders occurred in 75.6% of suicide attempters vs 15.2% without attempts, most commonly substance use disorder (SUD [46.5%]) and major depressive disorder (MDD [46.3%]).
Familial analyses included the 1,164,125 paternal half-siblings, 3,477,548 father-offspring, 4,992,249 full-siblings, 3,653,013 mother-offspring, and 908,740 maternal half-sibling pairs. Suicide attempt risk was elevated among relatives of affected people and highest in mother-offspring pairs with an odds ratio (OR) of 3.36 (95% confidence interval [CI]: 3.28-3.45). First-degree relatives showed stronger associations compared to second-degree relatives, which indicates genetic influence. Risk was greater among maternal half-siblings (OR = 1.80; 95% CI: 1.72-1.89) compared to paternal half-siblings (OR = 1.58, 95% CI: 1.50-1.66), which suggests shared environmental effects.
Sex-specific analyses demonstrated stronger aggregation in females, especially mother-daughter pairs (OR = 3.48, 95% CI: 3.37-3.61), female full-sibling pairs (OR = 3.66, 95% CI: 3.47-3.87) compared to father-son pairs (OR = 3.02, 95% CI: 2.91-3.14) and male full siblings (OR = 3.36, 95% CI: 3.16-3.57). There was a stronger suicide attempt aggregation observed in same-sex pairs compared to cross-sex pairs. Similarly, a stronger genetic correlation (rg) was also observed between male and female suicide attempts, with an rg of 0.85 (95% CI: 0.80-0.99) and p <0.001.
Familia coaggregation analyses also revealed an increased risk of psychiatric disorders among the relatives, particularly post-traumatic stress disorder (rg = 0.80, 95% CI: 0.77-0.96), SUD (rg = 0.85, 95% CI: 0.83-0.96), and MDD (rg = 0.77, 95% CI: 0.72-0.86), and with stronger effects in first-degree relatives. Self-harm heritability was found to be 42.3% (95% CI: 37.0-47.9), similar to that of suicide attempts, but genetic correlations with psychiatric disorders were 9-43% lower.
Limitations of the study include possible underestimation due to reliance on register data, unadjusted secular changes, limited generalizability beyond Sweden, exclusion of gene-environment interactions, and the potential inflation of heritability estimates.
In conclusion, sex differences were observed in the familial aggregation of suicide attempts, but heritability estimates were similar across sexes. Genetic liability contributes to suicide attempt risk, whereas non-genetic factors and sex-specific family history may improve suicide prevention strategies. Overall, these study findings support integrating familia and sex-specific information into suicide prevention approaches, which may help policymakers and healthcare systems better target and assess interventions aimed at improving mental health outcomes.
Reference: Nguyen T, Gong T, Hu K, et al. Sex differences in familial risk and genetic components of suicide attempts: a register-based cohort study in Sweden. BMJ Mental Health. 2026;29:e302082. doi:10.1136/bmjment-2025-302082
