Adverse childhood experiences, morbidity, mortality and resilience in socially excluded populations: protocol for a systematic review and meta-analysis

INTRODUCTION: Socially excluded populations, defined by homelessness, substance use disorder, sex work or criminal justice system contact, experience profound health inequity compared with the general population. Cumulative exposure to adverse childhood experiences (ACEs), including neglect, abuse and household dysfunction before age 18, has been found to be independently associated with both an increased risk of social exclusion and adverse health and mortality outcomes in adulthood. Despite this, the impact of ACEs on health and mortality within socially excluded populations is poorly understood. METHODS AND ANALYSIS: We will search MEDLINE, Cumulative Index of Nursing and Allied Health Literature, Educational Resources Information Center, PsycINFO, Applied Social Science Index and Abstracts and Criminal Justice Database for peer-reviewed studies measuring ACEs and their impact on health and mortality in socially excluded populations. Three review questions will guide our data extraction and analysis. First, what is the prevalence of ACEs among people experiencing social exclusion in included studies? Second, what is the relationship between ACEs and health and mortality outcomes among people experiencing social exclusion? Does resilience modify the strength of association between ACEs and health outcomes among people experiencing social exclusion? We will meta-analyse the relationship between ACE exposure and health outcomes classified into six a prior categories: (1) substance use disorders; (2) sexual and reproductive health; (3) communicable diseases; (4) mental illness; (5) non-communicable diseases and (6) violence victimisation, perpetration and injury. If there are insufficient studies for meta-analysis, we will conduct a narrative synthesis. Study quality will be assessed using the MethodologicAl STandards for Epidemiological Research scale. ETHICS AND DISSEMINATION: Our findings will be disseminated in a peer-reviewed journal, in presentations at academic conferences and in a brief report for policy makers and service providers. We do not require ethics approval as this review will use data that have been previously published. PROSPERO REGISTRATION NUMBER: CRD42022357565.