Associations of mental disorders in children with parents' subsequent mental disorders: nationwide cohort study from Finland and Denmark.

Background: Intergenerational transmission of mental disorders has been well established, but it is unclear whether exposure to a child's mental disorder increases parents' subsequent risk of mental disorders.

Aims: We examined the association of mental disorders in children with their parents' subsequent mental disorders.

Method: In this population-based cohort study, we included all individuals with children born in Finland or Denmark in 1990-2010. Information about mental disorders was acquired from national registers. The follow-up period began when the parent's eldest child was 5 years old (for ICD-10 codes F10-F60) or 1 year old (for codes F70-F98) and ended on 31 December 2019 or when the parent received a mental disorder diagnosis, died, or emigrated from Finland or Denmark. The associations of mental disorders in children with their parents' subsequent mental disorders were examined using Cox proportional hazards models.

Results: The study cohort included 1 651 723 parents. In total, 248 328 women and 250 763 men had at least one child who had been diagnosed with a mental disorder. The risk of a parent receiving a mental disorder diagnosis was higher among those who had a child with a mental disorder compared with those who did not. For both parents, the hazard ratios were greatest in the first 6 months after the child's diagnosis (hazard ratio 2.04-2.54), followed by a subtle decline in the risk (after 2 years, the hazard ratio was 1.33-1.77).

Conclusion: Mental disorders in children are associated with a greater risk of subsequent mental disorders among their parents. Additional support is needed for parents whose children have been recently diagnosed with a mental disorder.