Beginning in the mid-1990s, the construct of historical trauma was introduced into the clinical and health science literatures to contextualize, describe, and explain disproportionately high rates of psychological distress and health disparities among Indigenous populations. As a conceptual precursor to racial trauma, Indigenous historical trauma (IHT) is distinguished by its emphasis on ancestral adversity that is intergenerationally transmitted in ways that compromise descendent well-being. In this systematic review of the health impacts of IHT, 32 empirical articles were identified that statistically analyzed the relationship between a measure of IHT and a health outcome for Indigenous samples from the United States and Canada. These articles were categorized based on their specific method for operationalizing IHT, yielding 19 articles that were grouped as historical loss studies, 11 articles that were grouped as residential school ancestry studies, and three articles that were grouped as "other" studies. Articles in all three categories included diverse respondents, disparate designs, varied statistical techniques, and a range of health outcomes. Most reported statistically significant associations between higher indicators of IHT and adverse health outcomes. Analyses were so complex, and findings were so specific, that this groundbreaking literature has yet to cohere into a body of knowledge with clear implications for health policy or professional practice. At the conceptual level, it remains unclear whether IHT is best appreciated for its metaphorical or literal functions. Nevertheless, the enthusiasm surrounding IHT as an explanation for contemporary Indigenous health problems renders it imperative to refine the construct to enable more valid research.

The American Indian historical trauma (HT) concept is an important precursor to racial trauma (RT) theory that reflects the distinct interests of sovereign Indigenous nations but shares much of the same promise and challenge. Here, that promise and challenge is explored by tracing HT’s theoretical development in terms of its anti-colonial ambitions and organizing ideas. Three predominant modes of engaging HT were distilled form the literature (HT as a clinical condition, life stressor, and critical discourse), each informing a research program pursuing a different anti-colonial ambition (healing trauma, promoting resilience, practicing survivance) organized by distinct ideas about colonization, wellness, and Indigeneity. Through critical reflection on these different ambitions and dialogue of their organizing ideas, conflict between research programs can be mitigated and a more productive anti-colonialism realized in psychology and related health fields. Key recommendations emphasized clarifying clinical concepts (e.g., clinical syndrome vs. idiom of distress), disentangling clinical narratives of individual pathology (e.g., trauma) from social narratives of population adversity (e.g., survivance stories), attending to features of settler-colonialism not easily captured by heath indices (e.g., structural violence), and encouraging alignment of anti-colonial efforts with constructive critiques establishing conceptual bridges to disciplines that can help to advance psychological understandings of colonization and Indigenous wellness (e.g., postcolonial studies). This conceptual framework was applied to the RT literature to elaborate similar recommendations for advancing RT theory and the interests of ethnic/racial minority populations through engagement with psychology and related health fields.

Moving forward, it will be important for researchers to examine individual psychotherapy for Indigenous clients and to consider treatment for disorders unrelated to substance use. A preference for the inclusion of cultural practices and education in psychotherapy was clear across the literature, but the limited inferences that can be drawn from the existing research make it impossible to come to any conclusions about the specific roles or effects of cultural practices. Overall, empirical research is badly needed for psychotherapy with Indigenous populations at this time. (PsycINFO Database Record

Indigenous scholars and others who study the experiences of Indigenous communities have long criticized the psychocentric approach to trauma held by most clinical professionals. A recent example of this was the Canadian government's reparations for Indian Residential School system (IRS) survivors, which focused largely on individual psychological harms rather than broader effects of colonial oppression. Beginning in 1867 and continuing throughout the latter half of the twentieth century, Indigenous children were routinely removed from their home communities in Canada and placed into the IRS system, where they were frequently subject to physical, psychological, and sexual abuse. Using thematic analysis, this study draws on survivor testimonies from one residential school to explore how their descriptions of the effects and healing from IRS abuses differ from psychocentric understandings of trauma and loss. Results indicate that survivors describe IRS effects in sociocentric, ecocentric, and cosmocentric terms more so than psychocentric ones and place deep importance on healing through connection to family, culture, and community. To decolonize itself as a discipline and better serve Indigenous communities, the field of psychology must open up to understandings of trauma, loss, and healing that decentralize the individual, a difficult task given the discipline's psychocentric nature.

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