The Intergenerational Transfer of Mental Disorders: A Population-Based Multigenerational Linkage Study: Le transfert intergénérationnel des troubles mentaux : une étude sur les liens multigénérationnels basée sur la population

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 Objectives Both 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.Methods This 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.Results The 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.Conclusions Having 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. Objectifs L'& eacute;tiologie des troubles mentaux implique des facteurs g & eacute;n & eacute;tiques et environnementaux tous deux refl & eacute;t & eacute;s dans les ant & eacute;c & eacute;dents m & eacute;dicaux de la famille. Nous avons examin & eacute;, dans la population, la transmission interg & eacute;n & eacute;rationnelle de multiples troubles mentaux des parents et des grands-parents, & agrave; l'aide d'ant & eacute;c & eacute;dents familiaux objectivement mesur & eacute;s.M & eacute;thodes Cette & eacute;tude de cohorte r & eacute;trospective bas & eacute;e sur la population a utilis & eacute; des bases de donn & eacute;es administratives sur les soins de sant & eacute; au Manitoba, Canada, et comportait des adultes vivant au Manitoba de 1977 & agrave; 2020 et ayant des liens avec au moins un parent et un grand-parent. La date d'indexation & eacute;tait celle o & ugrave; les individus avaient 18 ans ou le 1er avril 1977, selon la date la plus tardive. Les diagnostics de trouble mental (humeur et anxi & eacute;t & eacute;, usage de substances, et troubles psychotiques) ont & eacute;t & eacute; identifi & eacute;s chez les personnes, les parents et grands-parents d'apr & egrave;s les dossiers d'hospitalisations et de clients ambulatoires. Les mod & egrave;les de r & eacute;gression & agrave; risques proportionnels de Cox incluaient les caract & eacute;ristiques sociod & eacute;mographiques, la comorbidit & eacute; individuelle et les ant & eacute;c & eacute;dents de troubles mentaux chez un grand-parent, une m & egrave;re et un p & egrave;re.R & eacute;sultats Sur les 109 359 personnes n'ayant pas de trouble mental avant la date d'indexation, 47,1 % & eacute;taient des femmes, 36,3 % avaient un trouble mental durant le suivi, et 90,9 % avaient un parent ou un grand-parent ayant des ant & eacute;c & eacute;dents de trouble mental avant la date d'indexation. Les ant & eacute;c & eacute;dents tant paternels que maternels d'un trouble mental augmentaient le risque du trouble chez les personnes. Les troubles psychotiques pr & eacute;sentaient l'association la plus forte avec les ant & eacute;c & eacute;dents parentaux et & eacute;taient surtout influenc & eacute;s par les ant & eacute;c & eacute;dents paternels (rapport de risque [RR] 3,73, intervalle de confiance & agrave; 95 % [IC] 2,99 & agrave; 4,64) comparativement aux ant & eacute;c & eacute;dents maternels (RR 2,23, IC & agrave; 95 % 1,89 & agrave; 2,64). Les ant & eacute;c & eacute;dents des grands-parents & eacute;taient ind & eacute;pendamment associ & eacute;s 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 & agrave; 95 % 1,34 & agrave; -1,50).Conclusions Les ant & eacute;c & eacute;dents parentaux des troubles mentaux & eacute;taient associ & eacute;s & agrave; un risque accru de tous les troubles mentaux. Les ant & eacute;c & eacute;dents de troubles mentaux des grands-parents & eacute;taient associ & eacute;s & agrave; une l & eacute;g & egrave;re augmentation du risque de troubles au-del & agrave; de l'influence des ant & eacute;c & eacute;dents parentaux. Cette & eacute;tude sur trois g & eacute;n & eacute;rations souligne en outre la n & eacute;cessit & eacute; de programmes d'intervention ax & eacute;s sur la famille aupr & egrave;s des familles touch & eacute;es par des troubles mentaux.