Background Chronic medical conditions (CMCs) and poverty commonly co-occur and, while both have been shown to independently increase the risk of perinatal mental illness, their collective impact has not been examined.
Methods This population-based study included 853 433 Ontario (Canada) women with a singleton live birth and no recent mental healthcare. CMCs were identified using validated algorithms and disease registries, and poverty was ascertained using neighbourhood income quintile. Perinatal mental illness was defined as a healthcare encounter for a mental health or substance use disorder in pregnancy or the first year postpartum. Modified Poisson regression was used to test the independent impacts of CMC and poverty on perinatal mental illness risk, adjusted for covariates, and additive interaction between the two exposures was assessed using the relative excess risk due to interaction (RERI) and synergy index (SI).
Results CMC and poverty were each independently associated with increased risk of perinatal mental illness (CMC vs no CMC exposure: 19.8% vs 15.6%, adjusted relative risk (aRR) 1.21, 95% CI (CI) 1.20 to 1.23; poverty vs no poverty exposure: 16.7% vs 15.5%, aRR 1.06, 95% CI 1.05 to 1.07). However, measures of additive interaction for the collective impact of both exposures on perinatal mental illness risk were not statistically significant (RERI 0.02, 95% CI −0.01 to 0.06; SI 1.09, 95% CI 0.95 to 1.24).
Conclusion CMC and poverty are independent risk factors for perinatal mental illness and should be assessed as part of a comprehensive management programme that includes prevention strategies and effective screening and treatment pathways.
- epidemiology of chronic diseases
- mental health
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Contributors M-RF and HKB undertook the conception and design of the study, the analysis and interpretation of the data and the drafting of the manuscript. LCB, C-LD and SNV contributed to the interpretation of the data and critically revised the manuscript for important intellectual content. All of the authors approved the final version to be published and agreed to be accountable for all aspects of the work.
Funding We gratefully acknowledge the Canadian Institutes of Health Research for their support of this study through their Project Grant programme (376290). The funding agency had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; preparation, review or approval of the manuscript; or decision to submit the manuscript for publication.
Disclaimer This study was supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care. The opinions, results and conclusions reported in this paper are those of the authors and are independent of the funding sources. No endorsement by ICES or the Government of Ontario is intended or should be inferred. Parts of this material are based on data and information compiled and provided by the Canadian Institute for Health Information (CIHI). However, the analyses, conclusions, opinions and statements expressed herein are those of the author and not necessarily those of CIHI.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The use of data was authorised under section 45 of Ontario’s Personal Health Information Protection Act, which does not require review by a research ethics board.
Provenance and peer review Not commissioned; externally peer reviewed.
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 data sharing agreements prohibit ICES from making the dataset publicly available, access may be granted to those who meet pre-specified criteria for confidential access, available at www.ices.on.ca/DAS. 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.