The association between suicide attempts (SAs) in parents and children is unclear, and risk indicators for intergenerational transmission remain undocumented. We aimed to assess this association, considering the child's developmental period at the time of parents' attempted suicide, and the parental relation.

Using a prospective cohort design, nationwide population data were linked to the Psychiatric Central Register and National Patient Register for all individuals aged 10 years or older living in Denmark between 1980 and 2016. We assessed incidence rate ratios (IRRs) and cumulative hazards for children's first SA.

In a cohort of 4 419 651 children, 163 056 (3.7%) had experienced a parental SA. An SA was recorded among 6996 (4.3%) of the exposed children as opposed to 70112 (1.6%) in unexposed individuals. Higher rates were noted when a parental SA occurred during early childhood (0 ⩽ age < 2) [IRR, 4.7; 95% confidence interval (CI) 4.2–5.4] v. late childhood (6 ⩽ age < 13) (IRR, 3.6; 95% CI 3.4–3.8) when compared to those unexposed. Children exposed prior to age 2 had the highest rates of all sub-groups when reaching age 13–17 (IRR, 6.5; 95% CI 6.0–7.1) and 18–25 years (IRR, 6.8; 95% CI 6.2–7.4). Maternal SA (IRR, 3.4; 95% CI 3.2–3.5) was associated with higher rates than paternal (IRR, 2.8; 95% CI 2.7–2.9).

Parental SA was associated with children's own SA. Exposure during early developmental stages was associated with the highest rates. Early preventive efforts are warranted as is monitoring of suicide risk in the children from age 13.