According to the 2020 United States (US) Census, Multiracial people - those who identify as two or more races - grew faster than any other racial group in the US. Despite this trend, research, scholarship, and knowledge on the health and well-being of this population has struggled to keep pace with this growth, and the health of Multiracial people is still not well-understood. Early research from psychology and sociology focused on risk and resilience factors associated with individuals' Multiracial identities. However, patterns emerging from both national health statistics as well as etiologic health research suggest that Multiracial people experience elevated rates of poor cardiometabolic, respiratory, mental, and behavioral health compared to monoracial (single-race) groups. In California, the state with the largest Multiracial population, they are more likely than monoracial White people to be living in poverty, disabled, and lacking health insurance. In addition to these health outcomes, descriptive studies of large nationally-representative datasets show that Multiracial people have the highest mean adverse childhood experiences (ACEs) score. ACEs, also sometimes referred to as childhood or early life adversity, are traumatic events occurring during childhood or adolescence, and are associated with numerous physical, mental, and behavioral health outcomes. Several of these outcomes disproportionately affect Multiracial people, and are leading causes of death in the United States. The goal of this dissertation is to marry knowledge and methods from disparate disciplines in describing the epidemiology of childhood adversity, while centering the health experience of Multiracial Americans.

In chapter 2 of this dissertation, I examine whether the high mean ACE score in the Multiracial population is driven primarily by Multiracial people with American Indian/Native American (AI/NA) ancestry, the largest subgroup of Multiracial people. AI/NA populations also have a high mean ACE score, possibly reflecting the legacy of occupation of Indigenous land and structural racism affecting generations of AI/NA peoples — what I call the "land occupation" hypothesis. This study found that estimates of mean ACE scores and risk of most ACE components were not significantly higher for Multiracial people with AI/AN ancestry than those without. These results suggest that the high mean ACE score is likely due to factors independent of the land occupation hypothesis. Further research should investigate causes of the disparities in ACEs between Multiracial and monoracial groups.

Chapter 3 of this dissertation investigates racial differences in the association between ACEs and some of the health outcomes disproportionately affecting Multiracial people, including metabolic syndrome, hypertension, asthma, anxiety, depression, suicidal ideation, and problematic drug use. Like in other interaction analyses, a goal of this study is to identify populations most affected and thus most urgently in need of intervention. Associations between ACEs and mental and behavioral health outcomes were strongest across racial groups. While Multiracial people do experience stronger associations between ACEs and anxiety than other racial groups, overall, the strength and direction of association varies by outcome, group, and interaction scale, with no group uniformly experiencing stronger associations than others.

Chapter 4 discusses some limitations to interaction analyses such as the one in chapter 3, and offers stochastic substitution methods as an alternative approach with some important benefits for health disparities research. I simulate a stochastic health equity intervention that provides an answer to the question: "how many cases per 100 of depression would be averted in the population if the ACEs distribution of each racial group approximated that of the White group?" Results from this simulation show that the Multiracial group would benefit the most from such an intervention, a finding that would be masked if only interaction effects were considered.

Childhood adversity contributes significantly to poor health among the Multiracial population. Prevention of ACEs could be an important and effective health equity strategy to reduce disparities affecting this group. More research is needed to identify why Multiracial children are predisposed to experiencing adversity, as is greater attention to the patterns of socially-constructed risks that contribute to the unique health experience of Multiracial people in the US.