Article Text

Original research
Sex differences among children, adolescents and young adults for mental health service use within inpatient and outpatient settings, before and during the COVID-19 pandemic: a population-based study in Ontario, Canada
  1. John S Moin1,
  2. Simone N Vigod1,2,3,4,
  3. Lesley Plumptre4,
  4. Natalie Troke4,
  5. Miqdad Asaria5,
  6. Irene Papanicolas6,
  7. Walter P Wodchis1,4,7,
  8. Shauna Brail8,
  9. Geoff Anderson1
  1. 1Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada
  2. 2Women’s College Research Institute, Women’s College Hospital, Toronto, Ontario, Canada
  3. 3Department of Psychiatry, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
  4. 4ICES, Toronto, Ontario, Canada
  5. 5Department of Health Policy, The London School of Economics and Political Science, London, UK
  6. 6Brown University School of Public Health, Providence, Rhode Island, USA
  7. 7Institute for Better Health, Trillium Health Partners, Mississauga, Ontario, Canada
  8. 8Institute for Management & Innovation, University of Toronto Mississauga, Toronto, Ontario, Canada
  1. Correspondence to Dr John S Moin; sina_moin{at}


Objectives The pandemic and public health response to contain the virus had impacts on many aspects of young people’s lives including disruptions to daily routines, opportunities for social, academic, recreational engagement and early employment. Consequently, children, adolescents and young adults may have experienced mental health challenges that required use of mental health services. This study compared rates of use for inpatient and outpatient mental health services during the pandemic to pre-pandemic rates.

Design Population-based repeated cross-sectional study.

Setting Publicly delivered mental healthcare in primary and secondary settings within the province of Ontario, Canada.

Participants All children 6–12 years of age (n=2 043 977), adolescents 13–17 years (n=1 708 754) and young adults 18–24 years (n=2 286 544), living in Ontario and eligible for provincial health insurance between March 2016 and November 2021.

Primary outcome measures Outpatient mental health visits to family physicians and psychiatrists for: mood and anxiety disorders, alcohol and substance abuse disorders, other non-psychotic mental health disorders and social problems. Inpatient mental health visits to emergency departments and hospitalisations for: substance-related and addictive disorders, anxiety disorders, assault-related injuries, deliberate self-harm and eating disorders. All outcomes were analysed by cohort and sex.

Results During the pandemic, observed outpatient visit rates were higher among young adults by 19.01% (95% CI: 15.56% to 22.37%; 209 vs 175 per 1000) and adolescent women 24.17% (95% CI: 18.93% to 29.15%; 131 vs 105 per 1000) for mood and anxiety disorders and remained higher than expected. Female adolescents had higher than expected usage of inpatient care for deliberate self-harm, eating disorders and assault-related injuries.

Conclusions Study results raise concerns over prolonged high rates of mental health use during the pandemic, particularly in female adolescents and young women, and highlights the need to better monitor and identify mental health outcomes associated with COVID-19 containment measures and to develop policies to address these concerns.

  • COVID-19
  • Primary Health Care
  • Depression & mood disorders
  • Eating disorders

Data availability statement

Data may be obtained from a third party and are not publicly available. The dataset from this study is held securely in coded form at ICES. While legal data sharing agreements between ICES and data providers (eg, healthcare organisations and government) prohibit ICES from making the dataset publicly available, access may be granted to those who meet pre-specified criteria for confidential access, available at (email: das{at} The full dataset creation plan and underlying analytic code are available from the authors upon request, understanding that the computer programs may rely upon coding templates or macros that are unique to ICES and are therefore either inaccessible or may require modification.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:

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Strengths and limitations of this study

  • Strong observational study design using large, diverse and population based cohorts.

  • Outcomes are well-established mental health usage indicators used in routine reporting and peer-reviewed publications and are based on physician claims and data routinely provided by hospitals and emergency departments under Ontario’s public health insurance that provides comprehensive care to all residents.

  • Care received outside Ontario’s public health insurance programme for physician services, hospital and emergency departments are not included in the analysis.

  • Observational study design cannot provide evidence of causality between specific public health measures and mental health outcomes.

  • Analysis was stratified by age and sex but did not control for other potential individual-level confounders that might have changed over the study period.


The COVID-19 pandemic was declared by the WHO on 11 March 2020.1 On 15 March 2020, the Office of the Premier responded by declaring a provincial state of emergency in Ontario, Canada, which resulted in successive closure of all non-essential shops and services.2 For nearly 2 years, health officials and institutional decision-makers attempted to mitigate population-level risk of infection by implementing non-pharmaceutical interventions (NPI), such as social distancing, masking and the closing and reopening of various sectors, which included daycares, primary and secondary schools and post-secondary institutions.2 3 The use of various NPIs throughout the COVID-19 pandemic resulted in major disruptions to nearly all aspects of life and routines of children, adolescents and young adults, due to mass closures of schools, recreation centres, organisational activities and early employment opportunities. According to the Center for Diseases Control and Prevention4 and other literature in the field, youth up to 24 years of age experienced many challenges during this time, some distinct to specific age groups, others shared across age bands, including major changes in their daily routine (eg, having to physically distance from friends, family, places of worship and other social communities); breaks in the continuity of learning (eg, switching from in-person to virtual learning, missing out on supplementary and early education opportunities, access limitations to personal workspace, technology and connectivity at home)5 6; breaks in continuity of healthcare (eg, missed well-child and immunisation visits, limited access to mental, speech, occupational and other health services). Within some households, youth also suffered loss in security and safety (eg, housing and food insecurity, increased exposures to domestic violence and online harms, threats of physical illness and uncertainty for the future). For all youth but particularly late teens and young adults, they missed out on significant life events and rites of passage (eg, missing celebrations, prom, graduations, dating, frosh-week and in-person college activities, early employment opportunities and other milestone life events).4

It has been hypothesised that these COVID-19-related challenges could result in long lasting mental health distress and symptoms, and in increased usage of mental health services. Studies and reports have begun to surface in support of this hypothesis.4 7 In England over a quarter of children and young people reported sleep disruptions, and high cases of isolation, feeling lonely and fearful of leaving home because of COVID-19 early in the pandemic.8 Another study found increases in depressive symptoms among youth in the UK.9 A study from the USA showed that the socioeconomic impact on parents due to job losses, working from home and social isolation also impacted children, particularly when there was job loss in the family and social isolation, with elevated stress and cortisol levels among parents and their children.10 A study from 73 primary care clinics in the USA showed increases in visits for children for mood and eating disorders at the beginning of the pandemic.11 In Ontario, Canada, there are indications that use of acute care services for eating disorders were higher during the pandemic.12 13 Another study in Ontario found that there was an increase in the use of mental healthcare services during the pandemic, particularly among adolescent women.14 A systematic review of studies of college students also found that mental health problems during the COVID-19 pandemic occurred more often in women than men.15 A systematic review of studies of emergency department use by children and adolescents, showed increased visits for suicide-related issues in girls but not boys and increased visit rates for self-harm in adolescents.16

Our study builds on that literature by examining critical mental healthcare service indicators for both office-based physician services and inpatient settings such as emergency departments (EDs) and hospitals. We are also building on prior studies by extending the age range to include young adults, who were under-represented in prior research. We are also building on current evidence by examining additional mental health outcomes such as deliberate self-harm (DSH) and assault-related injuries, with observational data for the first 20 months of the pandemic. Using routinely collected health administrative data from Ontario, Canada, we sought to examine whether the rates of mental health visits had changed during the pandemic (March 2020 to November 2021) versus pre-COVID-19 patterns. Given the existing evidence on differences in the rates of use of specific mental health services related to the age and gender of children,14–16 we examined use by specific diagnostic categories and stratified the sample by age (children (6–12 years of age), adolescents (13–17 years) and young adults (18–24 years)) and sex.


We designed a population-based, repeated cross-sectional study, using unique encrypted identifiers at the individual level, including all children (6–12 years of age), adolescents (13–17 years) and young adults (18–24 years), living in Ontario, Canada and eligible for provincial health insurance between March 2016 and November 2021. The physician billing codes have been completed in the same manner before and after COVID-19. The diagnosis code is provided independently by the physician after the assessment is completed. The Ontario Registered Persons Database provides sex, age, postal code and dates of birth for all Ontario residents. Office visits for physicians and psychiatrists were obtained from the Ontario Health Insurance Plan (OHIP) database, which contains billing records for all publicly funded physician services provided. The Canadian Institute for Health Information’s National Ambulatory Care Reporting System (NACRS), Discharge Abstract Database (DAD) and Ontario Mental Health Reporting System (OMHRS) were used to identify mental health-related ED visits and hospitalisations. All study data were accessed through Data Analytic Services (DAS) at ICES (formerly the Institute for Clinical Evaluative Sciences), an independent research institute with the legal status permitting it to collect and analyse healthcare and demographic data without individual patient consent for health system evaluation and improvement under the Ontario’s health information privacy law.

A baseline measure of mental health rates of use was obtained from the pre-pandemic period (March 2016 to February 2020). Rates of use during the pandemic are based on usage starting from March 2020 until the end of November 2021. Data were provided by DAS for analysis in a quarterly format, providing 23 cross-sectional measures over time. All persons between the ages of 6 and 24 years, and who were OHIP insured were considered for inclusion in the study. Persons with missing IKN (ICES Key Number—unique encrypted identifier), birth date, sex, OHIP eligibility, non-Ontario residential status, or who had died prior to index date were excluded. Three cohorts were generated based on age: (1) children 6–12 years of age, (2) adolescents 13–17 years of age and (3) young adults 18–24 years of age. We used open cohorts and assessed at-risk time to allow for individuals to contribute time at risk for outcomes. Data for sex, age and service use were provided at the individual level.

Outcome measures

Primary outcomes were outpatient visits for mental illness by primary care providers and psychiatrists derived from OHIP physician billing claims, and inpatient ED visits and hospitalisations using International Classification of Diseases (ICD-9 and ICD-10) codes from OMHRS, DAD and NACRS. Given the large proportion of virtual visits after the pandemic,14 especially in primary care, both in person and virtual were aggregated. Outcomes for each cohort are as follows: Outpatient outcomes: mood and anxiety disorders (OHIP DXCODES 296, 300, 311), alcohol and substance abuse disorders (OHIP DXCODES 303, 304), other non-psychotic mental health disorders (OHIP DXCODES 301, 302, 306, 309) and social problems (OHIP DXCODES: 897, 898, 899, 900, 901, 902, 904, 905, 906, 909). Inpatient outcomes: (ED and hospitalisations): substance-related and addictive disorders, anxiety disorders, assault-related injuries, DSH and eating disorders. For a full list of diagnostic codes see supplementary section (online supplemental table 1).

Statistical analysis

Negative binomial regression with time and season as predictor variables, were used to model usage trends before the pandemic (March 2016 to February 2020) and visits rates per 1000. In the case of rare events in ED and hospitals, they were reported per 100 000. The log of the persons in each quarter was used as the offset. Residuals were modelled as an autoregressive AR(1) process to account for serial correlation and to account for seasonality. The fitted model was used to predict the expected rates of use from March 2020 to the end of November 2021. For the main analysis, we calculated actual observed rates of use during the pandemic as compared with expected rates. Absolute difference of use for each quarter from March 2020 to the end of November 2021 was calculated by subtracting expected rates from observed rates. We calculated the relative difference (95% CI) between the observed and expected rates by subtracting the expected rate from the observed, divided by expected and multiplied by 100. We also stratified results from the primary analysis by individual diagnoses and sex. Data preparations, analyses and visualisations were performed using SAS V.9.4.

Patient and public involvement



Over 6 million youth between the ages of 6 and 24 years from Ontario, Canada were included in this study. The child cohort had a mean age of 7.7 (SD=2.1) years of which 48.6% were women, the adolescent cohort a mean age of 13.9 (1.4), 48.6% women and the young adult cohort a mean age of 19.9 (2.2) years with 48.8% women (online supplemental table 2).

Overall outpatient mental healthcare usage

Overall baseline expected rates of mental health service usage were lowest in the children cohort, followed by adolescent and then young adult cohorts (figure 1). In all three groups, the first quarter of the pandemic was associated with lower than expected rates. In the child cohort, the highest relative difference in rates for overall service usage were among women in March to May 2021 by 22.57% (95% CI: 18.14% to 26.8%; 33 vs 27 per 1000). In the adolescent cohort, the highest difference in the rate of use was in June to August 2021 by 24.17% (95% CI: 18.93% to 29.15%; 131 vs 105 per 1000) among women. Young female adults had the highest difference in service use, during December 2020 to February 2021 quarter, up by 19.01% (95% CI: 15.56% to 22.37%; 209 vs 175 per 1000). For women in all three cohorts, overall rates of mental healthcare use remained above expected rates during the pandemic. In contrast, men showed lower overall usage of mental health services relative to pre-pandemic levels, especially among children and adolescents. For more details (online supplemental table 3).

Figure 1

Total expected and observed outpatient mental health visits by age and sex.

Outpatient mental healthcare usage by individual diagnoses

Examining the change in individual diagnoses during the pandemic, revealed that the highest difference in mental healthcare use is attributable to mood and anxiety disorders, increasing with age across cohorts, particularly among women (figure 2). The highest relative difference in usage for mood and anxiety disorders was among female children 27.42% (95% CI: 22.93% to 31.72%; 23 vs 18 per 1000), although absolute rates remained low. Adolescent women and young adults showed much higher and persistent overall differences in service usage for mood and anxiety disorders. The highest differences in adolescent women were observed in the March to May 2021 quarter 19.8% (95% CI: 14.23% to 25.14%; 118 vs 112 per 1000) and June to August 2021 quarter 23.18% (95% CI: 17.4% to 28.64%; 117 vs 95 per 1000). The highest differences in adult women were observed in the December 2020 to February 2021 quarter 19% (95% CI: 15.09% to 22.93%; 183 vs 154 per 1000) and March to May 2021 quarter 18.2% (95% CI: 13.6% to 22.6%; 200 vs 169 per 1000). Other non-psychotic disorders were also higher during the pandemic, predominantly among female adolescents, but with low overall rates. Among all three male cohorts, we saw significantly lower usage of outpatient care for all disorders during the pandemic, especially among adolescents and young adults. However, higher rates of substance and alcohol abuse was observed among young male adults in March to May 2021 by 16% (95% CI: 11.4% to 20.33%; 15 vs 13 per 1000) (online supplemental figure 1). Other conditions did not show any substantial change between expected rates of use versus observed rates.

Figure 2

Expected versus observed mental health visits by age and diagnosis (women).

Inpatient mental healthcare usage in ED and hospitals

The difference in mental health service usage during the pandemic for ED and hospital services (online supplemental figure 2) showed that there was a general decrease in seeking care for mental health services within those settings, although care was available after the pandemic. The overall decrease during the pandemic was evident among all three cohorts, with exception of certain ED and hospital services among female adolescents (figure 3).

Figure 3

Total hospitalisations (women).

ED visits for DSH were up among adolescent women, with the highest difference in September to November 2021 by 42.8% (95% CI: 22.4% to 59.7%; 258 vs 181 per 100 000). In the same time frame, there was also a higher number of ED visits for DSH requiring hospitalisation by 46.1% (95% CI: 26.5% to 62.6%; 110 vs 80 per 100 000). Hospitalisations for DSH were also up among female adolescents, in September to November 2021 by 102.4% (95% CI: 76.4% to 123%; 354 vs 175 per 100 000).

Assault-related ED visits that required hospitalisation were up nearly fivefold for female adolescents 493.4% (95% CI: 238.5% to 565.2%; 2 vs 0.4 per 100 000) in September to November 2021. Assault-related hospitalisations were up more than twofold among female adolescents 272.7% (95% CI: 151.2% to 372.6%; 3 vs 1 per 100 000) during the September to November 2021 quarter.

Eating disorders were also higher among female adolescents, with a twofold difference in ED relative to expected rates 225.1% (95% CI: 178.6% to 256.9%; 59 vs 18 per 100 000), observed in September to November 2021 and comparably in March to May 2021. ED visits for eating disorders requiring hospitalisation were also up among female adolescents, highest in September to November 2021 by 221.3% (95% CI: 162.4% to 258.4%; 27 vs 8 per 100 000). The highest absolute difference in hospitalisations for eating disorders among female adolescents was in March to May 2021 by 139.7% (95% CI: 112.4% to 161%; 64 vs 26 per 100 000).


In this population-based repeated cross-sectional study, we observed substantially higher rates for clinical mental health outpatient visits for mood and anxiety disorders, relative to expected patterns prior to the pandemic, in adolescent and young female adults. Overall mental health visits to EDs and hospitalisations were down relative to expected rates, with exception of DSH, eating disorders and assault-related injuries among female adolescents. This is further evidence, using mental health service use as an indicator, that there have been significant mental health challenges among young female adults and particularly female adolescents, during the pandemic.

Examining physician-based mental health service use by sex, revealed that a large proportion of the elevated use can be attributed to mood and anxiety disorders among female adolescents and young adults. This finding was not unexpected and has been reported in Canada and elsewhere in North American and European countries.14 17 18 Female adolescents showed the highest relative increase, possibly due to various stressors reported during the pandemic among female teenagers, such as disruptions to daily routines, school and inability to see their peers in person.19 Female adults had the highest absolute increase, which is not surprising given the same impacts on adolescents during the pandemic, in addition to pre-existing economic stressors placed on young adults in terms of finances, education, employment prospects, housing and other added pressures early in adulthood.20

In contrast to lower overall mental health service use among men, we noted higher alcohol and substance abuse among male young adults. The literature is mixed with respect to increased alcohol and substance use in this population during the pandemic.21 This may be because these studies often use cross-sectional data, which depending on the demographics, time point and sampling frame may yield different results. It should be noted that the increase in substance and alcohol abuse detected in this study was not substantial. The overall lower than expected rates of seeking mental healthcare among adolescent and young adult men is not surprising and is consistent with the literature, where this demographic is known for seeking less care, which may have worsened during the pandemic.22 Alternatively, it has been suggested that boys took part in more physical activity during the pandemic and enjoyed reduced stresses associated with lockdowns such as less daily structure and not going to school, which may have been protective.19 There may be a greater prevalence of mental health challenges among men, especially young adults, however, due to various factors, available care is usually underused in this population.23–25

There was no major change in mental health service use among young children. However, we do not believe that this is an indication of there being an absence of mental health needs in this cohort but perhaps challenges in communication between children and their parents at this stage of development.26 27 Based on the literature, we know that young children also experienced challenges due to changes in their routines, distancing from extended family and caretakers, missed opportunities for social and cognitive development, routine medical and wellness visits, in addition to potential exposures to stress as a result of economic pressures on parents in some households.4 10 28 29 In one study, parents reported negative impacts associated with closure of early childhood education and care facilities, and schools.30 Some parents reported negative impacts of these closures on their children’s social and emotional well-being, resulting in anxiety, boredom, under-stimulation and tantrums.30 Another study also found deterioration of children’s mental health during the pandemic, attributed largely to social isolation.31 It is possible that the early psychological impacts of the pandemic and related lockdown measures on children were not detectable based on this study design and data but will become more apparent downstream.

Inpatient services revealed that ED visits and hospitalisations were down relatively across the board and for most conditions, except for DSH, eating disorders and assault-related injuries among female adolescents. Similar findings have been reported elsewhere.13 32 33 To our knowledge, a similar study regarding DSH found no increase in ED and hospitalisation among adolescents and young adults.34 This is likely a result of methodology as they combined their sample of adolescent and young adults. Our study did not find any increase in DSH among young female adults but did find an increase among female adolescents. There is also indication of greater case severity based on relatively flat ED visits but increased ED visits requiring hospitalisation and overall hospitalisation numbers for DSH, eating disorders and assault-related injury. The increase in cases and severity has been reported in a prior study for eating disorders.13 While absolute numbers for these visits remain low, any increase within these segments of mental health warrants attention. Especially for visits resulting from assault, neglect and domestic abuse, among other risk factors for ACEs, which can lead to short-term and long-term psychological and physical health consequences.33 35–37 This is the first study to our knowledge to have examined service use for assault-related injuries at the population level during the pandemic within this segment of the population in Ontario. Studies elsewhere have noted increases in abusive physical and verbal interactions towards teens and children because of pandemic stressors on parents.32 33 38 Even though absolute rates remain low among the population for DSH, eating disorders and assault-related injuries, we find it troubling that ED and hospitalisations have increased during the pandemic, for these critically serious outcomes.

Explanations for these findings are complex and studies as to possible causes are ongoing. Plausible theories have centred around closure of schools, reduced access to family and friends and isolation due lockdown measures which have been associated with sleep disturbance, anxiety, depression among teens and post-secondary students.18 29 39–42 Students also experienced elevated stress, loneliness and had fears of missing out on social life, their own health, friends and family’s and uncertainties about the future.43 Economic pressures on families have also shown to impact the mental health of youth within the household, especially when there was loss of employment and trouble keeping up with household bills.10 28 29 With increased cost of living and economic pressures, it is also important to acknowledge the link between food insecurity, depression, anxiety and eating disorders. Food insecurity has been associated with poor physical and mental outcomes, possibly due to feelings of helplessness, shame and stress.44 Additionally, food insecurity has been associated with eating disorders.45–47 This is considering global challenges in supply chain disruptions, cost, access barriers and growing demand for food banks post-pandemic.48–50 Additionally, disturbance in pre-pandemic routines and general reduction in physical activity during the pandemic may also be a contributing factor, given the wealth of evidence regarding physical and psychological benefits of exercise versus deleterious effects of a sedentary lifestyle.29 51 Lastly, schools are not simply a place for learning, they are a place where students socialise, make connections with peers and staff, find a sense of purpose and a sense of self, and for many where they access critical services, such as tools for personal development, education, special learning and peer support and for some, food programmes or an escape from domestic troubles at home.5 38 52 Much of these benefits and critical services delivered at school were simply not available in a remote learning environment during the pandemic.


Studies with outcomes based on healthcare usage, may underestimate the true prevalence of those health outcomes, due to non-seeking of care or the seeking of care outside the medical establishment such as private clinics. The diagnostic codes from OHIP billing submitted by physicians have been validated by chart audit and have been found to be very sensitive and specific.53 These codes have been used for public reporting and for peer-reviewed research publications.13 14 54 We stratified the analysis by age and sex to highlight important distinctions in mental health service usage. However, we did not control for a range of other risk factors such as previous history of mental health diagnoses or social and racial factors known to be related to mental health service usage at the individual level. Changes in prevalence of these factors over the course of this 5-year study could confound our results. Our quasi-experimental study design cannot provide evidence of causality based on NPIs, other post-pandemic stressors and increases in mental health service use. We acknowledge that the rapid shift to virtual care may have resulted in greater accessibility to some of the mental health services described in this study and as a result drive higher service usage post-pandemic. However, studies looking at the shift to virtual care from in-person services in Ontario have shown that in cases of mental health, the overall use in services decreased among the general population during the first 9 months of the pandemic.55 Therefore, it is quite possible that the increase detected among children, adolescents and young adults in this study were unique to this subpopulation. Lastly, the results of this study, while generalisable to the population of Ontario, Canada, may not be generalisable to other jurisdictions where COVID-19 cases, containment policies, boundaries and population characteristics are different.


Over a 20-month course of the COVID-19 pandemic, we observed substantially higher rates of use for mental health physician services relative to pre-pandemic levels, predominantly among female adolescents and young adults. Higher usage was largely driven by services for mood, anxiety and depressive disorders within outpatient settings. The only notable difference in mental healthcare needs among men was for alcohol and substance use in young adults, which should be monitored in the future. We noted higher cases and severity for eating disorders, DSH and assault-related injuries among adolescent women in EDs and hospitals. Our study raises concerns about growing mental health needs among female adolescents and young adults during the pandemic, especially in critical areas such as depression, anxiety, DSH, eating disorders and assault-related injury and call for urgent action in policy and healthcare response. We also need to ensure that more research and interventions are mobilised to identify and address underlying causes of worsening mental health among female adolescents and young adults.

Data availability statement

Data may be obtained from a third party and are not publicly available. The dataset from this study is held securely in coded form at ICES. While legal data sharing agreements between ICES and data providers (eg, healthcare organisations and government) prohibit ICES from making the dataset publicly available, access may be granted to those who meet pre-specified criteria for confidential access, available at (email: das{at} The full dataset creation plan and underlying analytic code are available from the authors upon request, understanding that the computer programs may rely upon coding templates or macros that are unique to ICES and are therefore either inaccessible or may require modification.

Ethics statements

Patient consent for publication

Ethics approval

This research was approved by the research ethics board at the University of Toronto (RIS protocol number 41386).


We would like to sincerely thank Minnie Ho and Alexandru Titeu for their support, helping to make this and others studies possible. This study contracted ICES Data & Analytic Services (DAS) and used de-identified data from the ICES Data Repository, which is managed by ICES with support from its funders and partners: Canada’s Strategy for Patient-Oriented Research (SPOR), the Ontario SPOR Support Unit, the Canadian Institutes of Health Research and the Government of Ontario. The opinions, results and conclusions reported are those of the authors. No endorsement by ICES or any of its funders or partners is intended or should be inferred. Parts of this material are based on data and information compiled and provided by CIHI. However, the analyses, conclusions, opinions and statements expressed here are those of the author, and not necessarily those of CIHI. Postdoctoral Fellowship support provided by the University of Toronto Institute for Pandemics (IfP), an academic center dedicated to public health research and education on pandemic readiness, resilience, and recovery, at the Dalla Lana School of Public Health.


Supplementary materials

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.


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  • Contributors JSM: formal analysis, visualisation, validation, writing – original draft, review & editing. SNV: conceptualisation, validation, writing – original draft, review & editing. LP: data curation, project administration, writing – review & editing. NT: data curation, project administration, writing – review & editing. MA: validation, writing – review & editing. SB: validation, writing – review & editing. IP: validation, writing – review & editing. WPW: validation, writing – review & editing. GA: conceptualisation, funding acquisition, methodology, supervision, validation, writing – review & editing.

  • Funding This work was supported by the Canadian Institute of Health Research. Sponsor: 303157 CIHR grants, reference WI2-179943. Postdoctoral Fellowship funding provided by the University of Toronto Institute for Pandemics (IfP).

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.