Objectives: The aetiology of mental disorders involves genetic and environmental factors, both reflected in family health history. We examined the intergenerational transmission of multiple mental disorders from parents and grandparents using population-based, objectively measured family histories.
Methods: This population-based retrospective cohort study used administrative healthcare databases in Manitoba, Canada and included adults living in Manitoba from 1977 to 2020 with linkages to at least one parent and one grandparent. Index date was when individuals turned 18 or 1 April 1977, whichever occurred later. Mental disorder diagnoses (mood and anxiety, substance use and psychotic disorders) were identified in individuals, parents and grandparents from hospitalization and outpatient records. Cox proportional hazards regression models included sociodemographic characteristics, individual's comorbidity and mental disorder history in a grandparent, mother and father.
Results: Of 109,359 individuals with no mental disorder prior to index date, 47.1% were female, 36.3% had a mental disorder during follow-up, and 90.9% had a parent or grandparent with a history of a mental disorder prior to the index date. Both paternal and maternal history of a mental disorder increased the risk of the disorder in individuals. Psychotic disorders had the strongest association with parental history and were mostly influenced by paternal (hazards ratio [HR] 3.73, 95% confidence interval [CI] 2.99 to 4.64) compared to maternal history (HR 2.23, 95% CI, 1.89 to 2.64). Grandparent history was independently associated with the risk of all mental disorders but had the strongest influence on substance use disorders (HR 1.42, 95% CI, 1.34 to 1.50).
Conclusions: Parental history of mental disorders was associated with an increased risk of all mental disorders. Grandparent history of mental disorders was associated with a small risk increase of the disorders above and beyond parental history influence. This three-generation study further highlights the need for family-based interventional programs in families affected by mental disorders.
Plain language summary title: The Intergenerational Transfer of Mental Illnesses.
Objectifs: L’étiologie des troubles mentaux implique des facteurs génétiques et environnementaux tous deux reflétés dans les antécédents médicaux de la famille. Nous avons examiné, dans la population, la transmission intergénérationnelle de multiples troubles mentaux des parents et des grands-parents, à l’aide d’antécédents familiaux objectivement mesurés.
Méthodes: Cette étude de cohorte rétrospective basée sur la population a utilisé des bases de données administratives sur les soins de santé au Manitoba, Canada, et comportait des adultes vivant au Manitoba de 1977 à 2020 et ayant des liens avec au moins un parent et un grand-parent. La date d'indexation était celle où les individus avaient 18 ans ou le 1er avril 1977, selon la date la plus tardive. Les diagnostics de trouble mental (humeur et anxiété, usage de substances, et troubles psychotiques) ont été identifiés chez les personnes, les parents et grands-parents d’après les dossiers d’hospitalisations et de clients ambulatoires. Les modèles de régression à risques proportionnels de Cox incluaient les caractéristiques sociodémographiques, la comorbidité individuelle et les antécédents de troubles mentaux chez un grand-parent, une mère et un père.
Résultats: Sur les 109 359 personnes n’ayant pas de trouble mental avant la date d’indexation, 47,1 % étaient des femmes, 36,3 % avaient un trouble mental durant le suivi, et 90,9 % avaient un parent ou un grand-parent ayant des antécédents de trouble mental avant la date d’indexation. Les antécédents tant paternels que maternels d’un trouble mental augmentaient le risque du trouble chez les personnes. Les troubles psychotiques présentaient l’association la plus forte avec les antécédents parentaux et étaient surtout influencés par les antécédents paternels (rapport de risque [RR] 3,73, intervalle de confiance à 95 % [IC] 2,99 à 4,64) comparativement aux antécédents maternels (RR 2,23, IC à 95 % 1,89 à 2,64). Les antécédents des grands-parents étaient indépendamment associés au risque de tous les troubles mentaux mais avaient l’influence la plus forte sur les troubles d’usage de substances (RR 1,42, IC à 95 % 1,34 à -1,50).
Conclusions: Les antécédents parentaux des troubles mentaux étaient associés à un risque accru de tous les troubles mentaux. Les antécédents de troubles mentaux des grands-parents étaient associés à une légère augmentation du risque de troubles au-delà de l'influence des antécédents parentaux. Cette étude sur trois générations souligne en outre la nécessité de programmes d'intervention axés sur la famille auprès des familles touchées par des troubles mentaux.
Keywords: administrative data; antécédents des grands-parents; antécédents familiaux; cohort study; données administratives; family history; grandparent history; lien multigénérationnel; mental disorders; multigenerational linkage; troubles mentaux; étude de cohorte.
ObjectivesBoth genetics and environmental factors, such as poverty, maltreatment and parental education, have a role in the development of mental illnesses. Some genetic and environmental risk factors for mental illnesses are shared within families. We conducted a large study to test the extent to which mental illnesses are passed down through generations.MethodsThis study used healthcare data from Manitoba, Canada captured during the delivery of healthcare services for administrative purposes. These data included all adults from 1977 to 2020 who had at least one parent and one grandparent with linked data. Mental illnesses were diagnosed in individuals, parents and grandparents by doctors during hospitalizations or physician visits. The illnesses included mood and anxiety, substance use, and psychotic illnesses. We estimated the likelihood of developing a mental illness when parents and/or grandparents had a mental illness as well.ResultsThe study included 109,359 individuals; a third developed a mental illness during the study period. The majority had a history of a mental illness in a parent or grandparent. We found that a history of mental illness in a mother and father increased the chance of developing the illness. Psychotic illnesses had the strongest relation with parental history. In particular, having a father with a psychotic illness increased the chance of developing the illness by four times. The likelihood of developing a mental illness was higher if a grandparent had a mental illness, above and beyond parental history influence, particularly for substance use disorders.ConclusionsHaving a parent or grandparent with a mental illness increases an individual's chance of developing a mental illness. Family-based intervention programs are needed to support families affected by mental illnesses in coping with their heavy burden.