Studies on the transmission of suicide risk have focused on parental history of suicide attempts (SAs), overlooking when the attempt happened. This study examined how the offspring's risk of attempting or dying by suicide varied by the timing of a first parental SA and the sex of the parent who attempted suicide.

Participants were 59 469 members of the 1987 Finnish Birth Cohort. The Finnish Hospital Discharge and Cause of Death Registers were the sources for parental and offspring SAs and offspring suicide. Timing of parental SA was coded as before (pre-pregnancy and pregnancy) and after the child's birth [infant/toddler years (0–2 years), childhood (3–11 years), adolescence (12–17 years), and young adulthood (18–26 years)].

In the multivariate models, having a parent who attempted suicide increased the offspring's risk of attempting suicide (odds ratio (OR) = 1.77, 95% confidence interval (CI) 1.39–2.25), but not of dying by suicide. Compared to unexposed offspring, those exposed after child's birth were at higher risk of attempting suicide (OR = 1.90, 95% CI 1.46–2.47), specifically when the parent attempted during offspring's childhood, adolescence, and young adulthood. A first maternal SA increased offspring's risk of attempting suicide regardless of the timing.

The impact of a parental SA on offspring's risk of attempting suicide differed depending on the timing and sex of the parent who attempted suicide, suggesting that the transmission of suicide risk may occur through genetic as well as environmental factors. Our findings call for an intergenerational approach in suicide risk assessment.