Introduction

Studies are increasingly identifying the importance of early life experiences to people’s health throughout the life course. Individuals who have adverse childhood experiences (ACEs) tend to have more physical and mental health problems as adults that those who do not have ACEs and ultimately greater premature mortality. ACEs include harms that affect children directly or indirectly through their living environments. Individuals who have ACEs can be more susceptible to disease development through both differences in physiological development and adoption and persistence of health-damaging behaviours.

In this study, the authors present findings from a systematic review and meta-analysis of studies measuring associations between multiple ACEs and health outcomes. The primary outcomes of interest were pooled measures of relations between multiple ACEs and health outcomes. The analyses were restricted to exposure to at least four types of adversity during childhood, with individuals reporting no ACEs as the comparator.

Methods

The search strategy of this review focused on six categories of health outcomes: substance use, sexual health, mental health, weight and physical exercise, violence, and physical health status and conditions. Studies were excluded based on high-risk or clinical populations because of often few individuals with low ACE exposure in such populations. Included studies met the following criteria: cross-sectional, case control, or cohort study, using a cumulative measure of at least four ACEs spanning both direct and indirect types, focused predominantly of adults aged at least 18 years, a sample size of at least 100, and reported odds ratios (ORs, comparable statistics, or data to enable their calculation for a health outcome. Included articles were independently assessed for quality by two reviewers using criteria based on the standard principles of quality assessment. Studies received a point for each quality criterion that they met, for a maximum score of 7.

Results

Of 11621 references identified by the search, 37 included studies provided risk estimates for 23 outcomes, with a total of 253719 participants. Individuals with at least four ACEs were at increased risk of all health outcomes compared with individuals with no ACEs. Associations were:

• Weak or modest for physical inactivity, overweight or obesity, and diabetes (ORS of less than two)
• Moderate for smoking, heavy alcohol use, poor self-rated health, cancer, heart disease, and respiratory disease (ORs of two or three)
• Strong for sexual risk taking, mental ill health, and problematic alcohol use (ORs of more than three to six)
• Strongest for problematic drug use and interpersonal and self-directed violence (ORs of more than seven)

Discussion & Conclusion

This study is the first to synthesize evidence for the effect of multiple ACEs and measure the relative magnitude of associations with many of the lifestyle behaviours and health conditions that challenge public health globally. For all outcomes examined, pooled ORs indicated increased risk among individuals with at least four ACEs compared with those reporting none. The results suggest that to have multiple ACEs is a major risk factor for many health conditions. The outcomes most strongly associated with multiple ACEs represent ACE risks for the next generation. To sustain improvements in public health requires a shift in focus to include prevention of ACEs, resilience building, and ACE-informed service provision. The

Sustained prevention gains might require a shift in focus to include the early drivers of poor health. Policies that capture the environmental and societal causes of adversity in childhood offer new opportunities to address ACEs rather than just their consequences. Specifically, through the UN 2030 Agenda for Sustainable Development, countries have committed to action to meet 17 global Sustainable Development Goals (SDGs) by 2030. Though several SDGs address violence directly, many others support focus on broad ACEs and their risk factors (e.g., goal 3 (good health and wellbeing), goal 4 (quality education), and goal 10 (reduced inequalities)). The SDGs also place major focus on early childhood development as a means of securing lifelong health and provide strong political endorsement and a multisectoral framework for this approach.

Along with the outcomes covered in this analysis, studies are now identifying associations between multiple ACEs and broad harms to life prospects, including education, employment, and poverty. Strengthening understanding of the combined effect of ACEs across multiagency priorities should catalyze multidisciplinary prevention focused on early intervention. Collaborative, trauma-informed services can address the various adversities affecting individuals and families across the life course, providing integrated services to support individuals and reduce the likelihood that their own children in turn will be affected by ACEs.

This systematic review and meta-analysis identify the pervasive effects that childhood adversity can have on health across the life course, with exposure to multiple ACEs affecting all the health outcomes examined, including some of the leading causes of the global burden of disease. Outcomes showing the strongest relations with multiple ACEs (violence, mental illness, and problematic substance abuse) can represent ACEs for the next generation (exposure to parental domestic violence, mental illness, and substance use) and thus are indicative of the intergenerational effects that can lock families into cycles of adversity, deprivation, and ill health. Although research into ACEs is far from complete, a compelling case exists for increased international focus on prevention of ACEs, and implementation of policies that support a sustainable life-course approach to health.