The Associations of Mental Disorders in Children With Parents’ Subsequent Mental Disorders: A 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. We examined the association of mental disorders in children with their parents’ subsequent mental disorders. Methods In this population based-cohort study, we included all persons with children born in Finland or Denmark in 1990–2010. Information of mental disorder was acquired from national registers. The follow-up period began when the parent’s eldest child was 5 years old ( for codes F10–F60 ICD-10) or 1 year old (for codes F70–F98 of the ICD-10). Follow-up ended on December 31st, 2019, or when the parent received a mental disorder diagnosis, died, or emigrated from Finland or Denmark. We used the time to a parental mental disorder as the main outcome. Findings The study cohort included 1 651 723 parents. In total, 248 328 women and 250 763 men had at least one child who was 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 to those who did not. For both parents, the hazard ratios were greatest in the first six months after the child’s diagnosis, followed by a subtle decline in the risk. Interpretation Mental disorders in children were associated with a greater risk of subsequent mental disorders among their parents. Although shared genetic and environmental mechanisms plausibly explain a share of these associations, the time-dependent associations suggest that offspring mental disorders may temporarily increase parental risk of mental disorders. Additional support is needed for parents whose children have been recently diagnosed with a mental disorder. Funding European Research Council (ERC), Research Council of Finland, Lundbeck Foundation Evidence before this study We searched for titles and abstracts of articles published in Web of Science and PubMed from 1st January 1 1990 to 1st April 2024, using the following terms: ((parent* or maternal or paternal or mother* or father* or family or familial or care giver) and (generation* or intergeneration* or transmission) and (mental or psychiatric or alcohol or drug or substance or schizo* or depress* or mood disorder* or bipolar or personality or neurotic or somatoform or obsessive compulsive or eating disorder or anorexia or psychos* or psychotic). We additionally screened reference lists of identified articles. Our literature review indicated that, although the intergenerational transmission of mental disorders has been well established, it remains unclear whether child’s mental disorder increases the risk of parents’ mental disorders. Many earlier studies focused on those persons taking care of a family member with a mental disorder and where small in scale and used non-representative samples. Previous studies that explicitly examined the consequences of children’s mental disorders for their parents focused on specific disorders, such as schizophrenia and autism. Added value of this study In this cohort study of over 1.6 million parents from Finland and Denmark, we conducted a comprehensive investigation of whether mental disorders in children are associated with their parents’ subsequent risk of mental disorders. We examined the population-level associations across the full spectrum of mental disorders diagnosed in childhood, adolescence, and early adulthood. Our results demonstrate that, there was a time-dependent association of offspring mental disorder with subsequent risk of parental mental disorder. For both women and men, the risk of a parent receiving a mental disorder diagnosis was at its highest in the first six months following the child’s diagnosis. In contrast to the analyses including any diagnosis of a child, our results from the analyses limited to specific disorders showed that was observed among women, but not in men, across most of the children’s diagnostic categories. Our reslults across Finland and Denmark were generally consistent. Implication of all the available evidence Our results indicate that children’s mental disorders may temporarily increase their parents’ risk of mental disorders. Although shared genetic and environmental mechanisms are likely to explain a share of these associations, further research for specific mechanisms is needed. Parents whose children have been recently diagnosed with a mental disorder could potentially benefit from additional support. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The present study was funded by the European Union (ERC, MENTALNET, 101040247), the Research Council of Finland (354237 to CH; 339390 to ME), and Lundbeck Foundation (Fellowship R345-2020-1588 to OP-R). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Ethics Committee of the Finnish Institute for Health and Welfare approved the study plan (THL/184/6.02.01/2023:933). Data were linked with the permission of Statistics Finland (TK-53-1696-16), Statistics Denmark, and the Finnish Institute of Health and Welfare. According to Finnish and Danish law, informed consent is not required for register-based studies. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data for the present study is property of Statistics Finland, Finnish Institute of Health and Welfare, Statistics Denmark, and the Danish Health Data Authority. The data are available from these authorities, but restrictions apply.