Background: Rising concern surrounds youth mental health in Canada, with growing disparities between females and males. However, less is known about recent trends by other sociodemographic factors, including sexual orientation, ethnocultural background, and socioeconomic status. Methods: This study analyzed data from 96 683 youths aged 15-24 who participated in the nationally representative Canadian Community Health Survey (CCHS) between 2007 and 2022. Trends in absolute and relative inequalities in poor/fair self-rated mental health (SRMH) by sex, sexual orientation, racialized and Indigenous identity, and socioeconomic conditions were assessed. Results: The percent of youths reporting poor/fair SRMH quadrupled from 4.3% in 2007-08 to 20.1% in 2021-22. During the same period, absolute inequalities in SRMH increased by 9.9 percentage points (95% CI: 6.6, 12.9) for females compared to males, 11.4 percentage points (95% CI: 4.6, 18.2) for Indigenous versus non-racialized youth, and 15.4 percentage points (95% CI: 5.7, 25.1) for youth (aged 18-24) identifying as lesbian, gay, or bisexual (LGB) compared to heterosexual. Conclusion: The sustained deterioration in youth SRMH over the past decade and a half has been accompanied by widening inequalities across several dimensions important for health equity in Canada. Action is needed to identify and implement effective programs and policies to support youth mental health and address disparities.

The authors have declared no competing interest.

This study did not receive any funding

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:

This study was exempt from research ethics board approval as per the Canada Tri-Council Policy Statement Ethical Conduct for Research Involving Humans. The legislative authority to use data for the purpose of public health surveillance or research is provided by section 4 of the Department of Health Act31 and section 3 of the Public Health Agency of Canada Act.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the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

All data produced in the present work are contained in the manuscript