Cohort Profile: The Ontario Mental Health and Intersectionality Data Surveillance (Ontario-MINDS) Cohort

Why was the cohort set up?The twenty-first century has brought a burgeoning recognition of the central role of mental health and illness to overall population health.Mental and substance-use disorders are among the top five leading contributors to the global burden of illness, largely owing to the young age at first onset [1].It is estimated that one in five adolescents has a mental or substance-use disorder that will persist into adulthood [2] and nearly 75% of lifetime mental disorders have an onset before the age of 25 years [3].Among children and youth, mental and substance-use disorders are the leading contributor to the total burden of illness in high-income countries and are responsible for the largest proportion of years lived with disability [4, 5].However, these estimates do not reflect the full impact of these illnesses on the young people affected.The first onset of mental and substance-use disorders typically occurs during adolescence and early adulthood [3], which may lead to disruptions in social, academic, and professional development.If left untreated, mental disorders among children and adolescents may recur and become chronic [6, 7], potentially leading to poor trajectories into adulthood.These public health impacts are further compounded by the 7-to 10-year reduction in life expectancy faced by people with mental and substance-use disorders, largely attributable to the high prevalence of comorbid physical health conditions and a 12-fold higher risk of suicide [8].Suicide is currently the Key Features The Ontario Mental health and Intersectionality Data Surveillance (Ontario-MINDS) retrospective cohort was established to address the lack of longitudinal population-based data on child and youth mental health.The cohort includes youth born between 1992 and 1996 who resided in the province at any point prior to 12 years of age (N 831 957), created using population-based health administrative data. The cohort includes sub-cohorts: (i) the MOMBABY sub-cohort, which includes linkages to maternal socio-demographic and clinical data, and (ii) a migrant sub-cohort, which identifies first-and second-generation migrants by using linkages to immigration data. The cohort is followed up to age 30 years in the health administrative data to ascertain health service contacts for mental and substanceuse disorders, with continuous follow-up for 87.5% of the cohort as of 2022.Incident cases of psychotic disorder have also been identified. The data holdings include numerous socio-environmental variables, such as neighbourhood-level marginalization indicators and migrant status.The application of validated algorithms has enabled us to identify factors such as multimorbidity and health service encounters for adverse childhood experiences, and primary data linkages have facilitated the exploration of novel exposures, such as green space and air pollution throughout childhood. Collaborations with investigators interested in life-course approaches to youth physical and mental health are welcomed.Use of the Ontario-MINDS cohort may be granted with the permission of the principal investigator (PI) to those who meet pre-specified criteria for confidential access.