Longitudinal association between informal unpaid caregiving and mental health amongst working age adults in high-income OECD countries: A systematic review.

Background: Informal unpaid caregivers provide most of the world's care needs, experiencing numerous health and wealth penalties as a result. As the COVID-19 pandemic has highlighted, informal care is highly gendered. Longitudinal evidence is needed to assess the causal effect of caregiving on mental health. This review addresses a gap by summarising and appraising the longitudinal evidence examining the association between unpaid caregiving and mental health among working age adults in high-income Organisation for Economic Co-operation and Development (OECD) countries and examining gender differences. Methods: Six databases were searched (Medline, PsycInfo, EMBASE, Scopus, Web of Science, Econlit) from Jan 1, 2000 to April 1, 2022. Population-based, peer-reviewed quantitative studies using any observational design were included. Population of interest was working age adults. Exposure was any unpaid caregiving, and studies must have had a non-caregiving comparator for inclusion. Mental health outcomes (depression, anxiety, psychological distress/wellbeing) were measurable by validated self-report tools or professional diagnosis. Screening, data extraction and quality assessment (ROBINS-E) were conducted by two reviewers. The study was prospectively registered with PROSPERO (CRD42022312401). Findings: Of the 4536 records screened; 13 eligible studies (133,426 participants) were included. Overall quality of evidence was moderate. Significant between-study heterogeneity precluded meta-analysis, so albatross and effect-direction plots complement the narrative synthesis. Results indicate a negative association between informal unpaid care and mental health in adults of working age. Importantly, all included studies were longitudinal in design. Where studies were stratified by gender, caregiving had a consistently negative impact on the mental health of women. Few studies examined men but revealed a negative effect where an association was found. Interpretation: Our review highlights the need to mitigate the mental health risks of caregiving in working age adults. Whilst men need to be included in further scholarship, reducing the disproportionate caregiving load on women is a crucial requirement for policy development. Funding: Melbourne School of Population and Global Health, Targeted Research Support Grant.