Trauma and Substance Use among Indigenous Peoples of the United States and Canada: A Scoping Review

Abstract

Substance use has been identified by Indigenous populations as contributing to health disparities facing their communities. Rates of trauma exposure and post-traumatic stress disorder are higher in Indigenous, compared to non-Indigenous, populations and have been linked to substance use. Historical trauma is thought to be one mechanism underlying substance use and related disorders. The purpose of the present study is to summarize the current state of the literature focusing on the association between trauma (historical and lived) and substance use among Indigenous populations in the United States and Canada. Databases were systematically searched using the preferred reporting items for systematic reviews and meta-analyses statement. The search strategy initially yielded 4,026 articles. After exclusion of ineligible articles, 63 articles remained for synthesis. Results of the present review provide evidence for a positive link between substance use and both historical trauma (i.e., 86.4% of studies) and lived trauma (i.e., 84.7% of studies). Indigenous participants reported that historical trauma and pain related to loss of cultural identity contributed to substance use in their communities. Indigenous participants also consistently described an association between lived trauma and substance use. Despite heterogeneity among Indigenous communities, findings suggest a significant association between trauma and substance use across many different tribes and settings (e.g., reservation/reserve, rural/urban). Indigenous participants identified healing from trauma and reconnecting with culture as necessary components for reducing substance use and maintaining sobriety. With this, the development and implementation of interventions should partner with Indigenous communities in a manner that promotes and enhances cultural values for healing.

Introduction

Indigenous populations experience disproportionate rates of trauma and substance use. We use the term Indigenous to refer to the Indigenous peoples of the United States and Canada, including American Indian, Alaska Native, Native Hawaiian, and other native Pacific Islander peoples in the United States, and First Nations, Métis, Inuit, and other Aboriginal peoples in Canada, among others. Pre-colonization tribal sovereignty was often identified through tribal land that separated the continent based on its inhabitants. Thereafter, arbitrary borders were drawn through the continent, separating the United States and Canada to define and uphold European colonization of tribal lands and enforce new European autonomous governments. Consequently, Indigenous peoples and tribal lands were separated based on which side of the border they fell and were differentially categorized as American Indian tribes and First Nation bands. Thus, it is evident that the United States-Canada border is an “arbitrary, foreign imposition” (Depasquale et al., 2009, p. 12). While there is a tremendous amount of diversity and variability across Indigenous groups, it is important to note that many groups were split in half by the border, resulting in some groups today with communities in both the United States and Canada. Consequently, and incorrectly, these groups are often not seen as a united people (Depasquale et al., 2009). There has been growing interest in literature on the impact of trauma specific to Indigenous populations broadly—including historical trauma—and substance use.

Substance use (e.g., use of alcohol, cigarette/tobacco, marijuana, other illicit/licit substances) has been identified by Indigenous populations as among the most pressing health disparities facing their communities and as a major contributor to other health disparities (Spillane et al., 2020a). There is significant variability in rates of substance use across Indigenous communities, with some communities reporting high rates of substance use (Marrone, 2007) and others finding higher rates of abstinence compared to non-Indigenous individuals (Mitchell et al., 2003; Whitesell et al., 2012). Overall, Indigenous individuals report lower rates of past-year alcohol use compared to White (i.e., non-Hispanic or Multiracial people who self-identify as White, including persons with origins in Europe, the Middle East, or North Africa), Black, and Multiracial individuals (SAMHSA, 2021), but are more likely to use tobacco, marijuana, and inhalants (Falk et al., 2006; Mitchell et al., 2003; Spillane et al., 2020b). Among Indigenous adolescents, higher rates of substance use are found across nearly all substances compared to non-Indigenous peers (Beauvais et al., 2008; Nalven et al., 2020; Spillane et al., 2017; Stanley et al., 2021; Swaim & Stanley, 2018). Despite this variability in use, a well-established and consistent finding is that Indigenous individuals experience disproportionate problematic substance use as well as harm related to substance use compared to other racial/ethnic groups. For instance, Indigenous adults have among the highest rates of binge and heavy drinking (SAMHSA, 2021; Statistics Canada, 2011), as well as the highest rates of substance use disorders (SUDs), greater morbidity and mortality related to substance use, and the greatest unmet need for substance use treatment (Greenfield & Venner, 2012; Vaeth et al., 2017). Given these findings, there is a clear need to identify factors that contribute to risk for substance use in order to inform future prevention and treatment efforts that can lessen or ameliorate substance-related health disparities.

Rates of trauma exposure (i.e., events that are experienced by an individual as physically or emotionally harmful or threatening and that have lasting adverse effects on their functioning and well-being; Kirk-Provencher et al., 2020; Whitesell et al., 2012; M. T. Williams et al., 2018) and post-traumatic stress disorder (PTSD; Robin et al., 1997) are higher in Indigenous populations compared to non-Indigenous populations. Indigenous peoples have been found to be at four-times greater risk of experiencing any traumatic event compared to non-Indigenous people, ten-times greater risk of sustaining an injury due to an assault, five-times greater risk of experiencing motor vehicle crashes, and three-times greater risk of experiencing traumatic suicides (Karmali et al., 2005). In Canada, despite comprising less than 3% of the total population (Indigenous and Northern Affairs Canada, 2016), 10% of all missing women are Indigenous, and between 1980 and 2014, 16% of all female homicide victims were Indigenous women (Department of Justice Research and Statistics Division, 2018). In 2014, Indigenous women in Canada were victims of homicide at a rate of over six-times that of non-Indigenous Canadian women (Department of Justice Research and Statistics Division, 2018). In Canada, the startling rates of missing and murdered Indigenous women and girls has been deemed a genocide by their government (Kennedy, 2019). In the United States, murder is the third leading cause of death among Indigenous women (Urban Indian Health Institute, n.d.).

In addition to the high rates of lived trauma experienced by Indigenous individuals, there is growing attention on trauma specific to Indigenous communities. Specifically, historical trauma, defined as the “massive cumulative trauma across generations” (Brave Heart, 1998, pp. 287–289), is a collective, complex trauma inflicted on a group of people who share a specific group identity or affiliation—ethnicity, nationality, and/or religious affiliation (Evans-Campbell, 2008, p. 320). Historical trauma is the legacy of numerous traumatic events a community experiences over generations and encompasses the psychological and social responses to such events. Western colonization of North America resulted in historical trauma in Indigenous communities as it brought the systematic destruction and criminalization of traditional cultural activities; the forced removal of children from homes to be adopted by non-Indigenous families or sent to residential boarding and day schools, sending the message that Indigenous families were unsuitable for raising children (Evans-Campbell, 2008); and communicable diseases previously unknown to Indigenous populations such as tuberculosis, smallpox, influenza, and measles, which resulted in the decimation of Indigenous populations (Jones, 2006). Importantly, historical trauma does not refer specifically to events that occurred in history. Evans-Campbell (2008) identified three distinguishing characteristics of events associated with historical trauma: (a) they are experienced by and affect many Indigenous people at the time of the event; (b) they generate high levels of collective distress and mourning; and (c) they are usually perpetrated by outsiders purposefully and with destructive intent. As just one example of ways in which historical trauma continues to occur in the present day, hundreds of Indigenous children’s remains were found in unmarked mass graves at two residential schools in Canada in May and June 2021 alone (Coletta, 2021). Following these discoveries, the United States Department of the Interior (2021) and Secretary Deb Haaland announced plans to investigate the legacy of residential schools in the United States.

Extant research has demonstrated a link between trauma exposure and substance use (for reviews, see Halpern et al., 2018; Konkolÿ Thege et al., 2017). Several pathways have been identified which may underlie this link. The self-medication hypothesis posits that problematic substance use develops in response to trauma-related emotional distress (Khantzian, 1997). Specifically, individuals experiencing trauma symptoms may use substances to reduce or eliminate emotional distress, thus negatively reinforcing substance use. This may lead to substance use becoming an automatic escape response, increasing the likelihood of developing a SUD (Chilcoat & Breslau, 1998; Hawn et al., 2020; Khantzian, 1997). Alternatively, the high-risk hypothesis suggests that substance use causally influences risk for trauma exposure, perhaps because substance use may lead to increased engagement in other risky behaviors that increase the risk for subsequent exposure to a traumatic event (Chilcoat & Breslau, 1998). Finally, the shared vulnerability hypothesis suggests that common factors, including environmental factors such as early life stressors, may underlie risk for both trauma and substance use (Norman et al., 2012). Regardless of the reason for the association, extant research exploring the link between trauma exposure and substance use has identified the co-occurrence as highly clinically relevant (for a review, see Roberts et al., 2015).

Moreover, research suggests that historical trauma related to colonization offers etiological explanations for substance use and disorders (Whitesell et al., 2012). Specifically, the cumulative effects of historical trauma in Indigenous communities are transmitted intergenerationally as descendants continue to identify with the suffering of their ancestors (Evans-Campbell, 2008). This suffering may lead to substance use problems through the destruction of family or cultural rituals, lived traumatic experiences, family substance use, the removal of children from homes leading to decreased emotional support and disruptions in traditional parenting practices, and the use of substances to numb pain related to historical trauma (Brave Heart, 2003). Moreover, many Indigenous groups believe that historical trauma lies at the heart of substance use and mental illness within their communities (SAMHSA, 2019). In fact, with respect to alcohol use in particular, Indigenous people did not have distilled, potent forms of alcohol prior to European contact (Beauvais, 1998). Alcohol was introduced into Indigenous communities as a vehicle of colonization and a genocidal act to inhibit Indigenous peoples’ capacity to refuse trade offers and to gain negotiating advantages for traders (Beauvais, 1998; Duran, 2018; Frank et al., 2000). Further, likely partly due to colonization, there are many harmful cultural myths related to alcohol that likely influence alcohol use: The persistent stereotype-myth of the “drunken Indian” (Matamonasa-Bennett, 2017), as well as the “fire-water” myth (i.e., the notion that Indigenous groups are more vulnerable to alcohol problems due to biological or genetic differences) are problematic and can have negative effects on alcohol expectancies and drinking behavior among Indigenous groups (V. M. Gonzalez & Skewes, 2018). Overall, it is likely that the lasting effects of colonization and ongoing systemic racism against Indigenous communities and people have played a significant role in substance use and substance-related problems.

The purpose of the present study is to summarize the current state of the literature focusing on the association between trauma (both historical and lived, and both trauma exposure and trauma-related disorders [i.e., PTSD, acute stress disorder, and adjustment disorder]) and substance use among Indigenous populations. Given our aim to summarize research focusing on the Indigenous peoples of the United States and Canada, it is important to note that language used varies significantly across country, geographic region, and particular community (e.g., reservation vs. reserve, tribe vs. band in the United States vs. Canada). Thus, throughout this paper, we have chosen to mirror the language that was used in the article being described.

Methods

This scoping review followed the rreferred reporting items for systematic reviews and meta-analysis (PRISMA) statement (PROSPERO Registration # CRD42020212548; Moher et al., 2009). This review and team were led by an Indigenous scholar, and the study team included an Indigenous research assistant who assisted with identification of search terms.

Search Strategy

The following databases were searched on February 8, 2021: PubMed, PsycINFO, PsycARTICLES, Embase, MEDLINE, Social Services Abstracts, AnthropologyPLUS, and Web of Science. Search terms included (“Native American” OR “American Indian” OR “Alaska* Native*” OR “First Nation*” OR “Inuit” OR “Métis” OR “Indigeno*” OR “North American Indigenous” OR “Aboriginal” OR “Native Hawai*” OR “American Native Continental Ancestry Group” OR “Pacific Islander”) AND (“substance use” OR “substance abuse” OR “substance use disorder” OR “substance dependence” OR “addiction” OR “alcohol*” OR “drink*” OR “drug*”) AND (“trauma*” OR “posttraumatic*” OR “ptsd” OR “acute stress disorder” OR “intergenerational trauma” OR “historical trauma” OR “transgenerational trauma” OR “settler colonialism” OR “coloni*” OR “residential schools” OR “boarding schools” OR “adjustment disorder” OR “collective trauma” OR “multigenerational trauma” OR “soul wound”). All manuscripts generated using these search criteria were compiled into a database. Abstracts were screened by two independent reviewers to assess inclusionary criteria. Raters reached consensus on 94.2% of articles in the initial search. Discrepancies in coding were reviewed by a third independent reviewer to make final inclusionary determinations. Finally, reference lists of articles determined to meet inclusionary criteria were reviewed to identify other relevant articles that may not have been identified through searching databases. The search strategy and number of articles are illustrated in a flow diagram (see Figure 1).

Figure 1.

Flow diagram for systematic review procedures.

Eligibility Criteria

Articles were restricted based on four predetermined criteria: (1) reporting in English language, (2) empirical study, (3) population of focus is Indigenous (i.e., papers were included if their sample was entirely comprised of Indigenous peoples or if they reported results separately for an Indigenous subsample), and (4) primary purpose of paper is to examine the association between trauma and substance use (i.e., papers were excluded if they included both trauma and substance use as variables but did not examine their association).

Data Extraction and Synthesis

The remaining 63 full-length articles were reviewed and data relevant to study goals were extracted and compiled into tables. Information extracted from each article by two independent raters included: (1) sample demographics, (2) study characteristics, (3) description of trauma, (4) assessment of trauma, (5) description of substance use, (6) assessment of substance use, and (7) findings.

Results

Search Results

The search strategy yielded 4,026 articles and reviewing reference lists of articles found to meet inclusion criteria yielded an additional 14 articles. After removing duplicates, the search resulted in 2,033 unique articles. During the initial abstract review, 1,874 were excluded. Following the procedures outlined above, the remaining 159 articles were reviewed and 63 were determined to meet inclusionary criteria (see Figure 1). Among the articles excluded at full-text review, 48 did not explicitly examine the association between trauma and substance use, 10 were not empirical studies (i.e., literature reviews), 19 did not focus on Indigenous populations, 1 was not in English, and 3 were duplicate articles. An additional 15 were excluded because, despite our best efforts, we were unable to obtain full-text versions. These final 63 articles were subsequently examined, and relevant information pertaining to study goals was extracted (see Data Extraction and Synthesis) and compiled into tables.

Sample Demographics

Sample demographics are summarized in Supplemental Table 1. The 63 included studies represented 66,003 Indigenous participants. Sample sizes ranged from 9 to 19,705, and the mean ages of study participants ranged from 7.87 to 51.68. Regarding gender or sex, five articles had samples entirely comprised of women, three articles had samples entirely comprised of men, and one article had a sample comprised entirely of Two-Spirit individuals.¹ Most authors described their samples as comprising American Indian/Native American individuals (n = 48). Some study authors described their participants as Aboriginal (n = 4) or Indigenous (n = 2). Seven study authors reported including Alaska Native participants, and two reported including Native Hawaiian participants, including one research team who described participants as Native Hawaiian and other Pacific Islander. Eleven articles reported including First Nation participants, and two reported including Inuit and Métis participants.

Study Characteristics

Study characteristics are summarized in Supplemental Table 2. Most studies used correlational survey designs (n = 42. 66.7%), while 16 (25.4%) were qualitative, and 1 (1.6%) used a mixed methods design. Many authors did not report on incorporating community engagement (n = 25). Authors of 5 studies reported that they followed the principles and practices of community-based participatory research, and 12 reported that they included input from community members in the research process, including 8 who assembled a community advisory board. Authors of fifteen studies reported that they obtained tribal approval and authors of one study reported that they obtained Indian Health Service approval to conduct the research project. Other examples of community engagement were the inclusion of traditional practices (n = 3), hiring Indigenous staff to carry out the project (n = 15), an author having a preexisting relationship with the community (n = 6), providing results back to the community (n = 1), noting that the data was partially owned by the community (n = 1), and seeking approval from the community prior to manuscript publication (n = 1). Authors of one study noted that the research was conducted “in full collaboration with the community,” without providing additional details. Additional details regarding sample and study details are summarized in Supplemental Table 3.

Association between Historical Trauma and Substance Use

Study results are summarized in Table 1. Of the 22 studies that focused on the relationship between historical trauma and substance use among Indigenous populations, 19 (86.4%) found evidence of a significant association. Six found that historical trauma was associated with increased risk of substance use (Pokhrel & Herzog, 2014), including alcohol use (Whitbeck et al., 2004; Wiechelt et al., 2012), cigarette smoking (Soto et al., 2015), illicit drug use (Wiechelt et al., 2012), and poly-drug use (Brockie et al., 2015). Ehlers, Gizer, Gilder, Ellingson, et al. (2013) found that individuals who met criteria for a lifetime alcohol and/or drug use disorder scored significantly higher on measures of historical trauma. Three studies focused specifically on the traumatic effects of residential boarding schools. Caregivers and older family members having experienced residential boarding school led to a forced disconnect with traditional culture, which increased risk for alcohol use (Rothe et al., 2006), injection drug use (Lemstra et al., 2012), and club drug, cocaine, and narcotic use (Evans-Campbell et al., 2012).

Table 1.

Study Findings.

Citation	Findings
Historical trauma
Brown et al. (2016)	Historical trauma was described by participants as contributing to ongoing alcohol use in communities.
Ehlers, Gizer, Gilder, Ellingson, et al. (2013)	Participants who met criteria for lifetime AUD or SUD scored significantly higher on measures of historical trauma.
Evans-Campbell et al. (2012)	Boarding school attendance was associated with significantly higher rates of alcohol abuse or dependence, and high rates of past 12-month use of club drug, cocaine, and narcotic use. Being raised by someone who had attended a boarding school was not associated with significantly higher rates of substance use.
Gone (2009)	Participants described pain passed down through generations from historical trauma leading to substance use. Healing from substance use will require reclaiming Indigenous heritage to counteract damage done by European colonization.
Henderson et al. (1998)	Individuals with a history of alcohol dependence were not more likely to have attended a boarding school.
Lemstra et al. (2012)	Attending a residential school or having a family member who attended a residential school was associated with significantly increased odds of injection drug use.
Luger (2019)	Historical trauma was not significantly associated with alcohol use.
Marsh et al. (2016)	Participants described substance use as a result of pain from loss of cultural identity and a way of managing their pain related to trauma and the intergenerational effects of colonization.
Matamonasa-Bennett (2017)	Participants reported that alcohol contributed to loss of cultural identity, is symbolic of colonization, and is a way of protesting colonization.
Myhra (2011)	Participants reported that their experiences with substance use were rooted in historical trauma and lack of connection with their culture. Reconnecting with culture can aid in combating substance use.
Pokhrel and Herzog (2014)	Historical trauma was significantly associated with substance use. Discrimination mediated the effect of historical trauma on substance use.
Rothe (2005)	Participants identified alcohol consumption as an outlet to deal with internal conflict related to historical trauma.
Rothe et al. (2006)	Participants reported that that there was a relationship between alcohol abuse and historical trauma related to intergenerational effects of residential schools. Many described family members feeling disconnected from their culture due to experiences with residential schools and drinking as a result.
Skewes and Blume (2019)	Participants described strong connections between SUDs and intergenerational trauma. Feelings of “helplessness” and loss of cultural identity were described as important factors in understanding poor community health and SUD. Revitalization of culture is a promising method to heal SUDs.
Trinidad et al. (2020)	Participants identified ongoing effects of colonialism as contributing to current alcohol use.
Whitbeck et al. (2004)	Past-year alcohol use was significantly associated with historical loss. Historical loss mediated the effect of discrimination on alcohol use among women.
Wiechelt et al. (2012)	Higher scores on historical trauma measures were associated with higher odds of current alcohol use and lifetime illicit drug use.
Lived trauma
Baldwin et al. (2011)	Experiencing a greater number of stressful life events was positively associated with reporting alcohol and marijuana use.
Beals et al. (2005)	PTSD diagnosis was associated with significantly increased risk for SUDs.
Boyd-Ball et al. (2006)	Experiencing two or more traumatic events significantly increased the odds of AUD. Trauma type did not significantly influence risk for AUD.
Burnette (2016)	Participants identified partner substance use as a risk factor for intimate partner violence.
Burnette and Renner (2017)	Participants experiencing intimate partner violence identified substance use is a problem in their relationship.
Currie et al. (2015)	PTSD symptom severity was significantly positively associated with drug problems. Childhood physical and sexual abuse were not significantly associated with drug problems.
DeBruyn et al. (1992)	Parent alcohol abuse was more commonly identified in medical records of children experiencing child abuse and neglect than for children not experiencing abuse and neglect.
Deters et al. (2006)	Of participants in substance use treatment, 98% reported experiencing at least one traumatic event. PTSD diagnosis was associated with increased odds of stimulant abuse or dependence, but not with odds of abuse or dependence related to any other substance.
Dick et al. (1993)	Stressful life events were significantly positively associated with frequency and quantity of alcohol use, but not with frequency of intoxication in the past month.
Dickerson et al. (2009)	High rates of lifetime nicotine dependence were observed for those with PTSD. PTSD diagnosis increased odds of lifetime, but not past-year, nicotine dependence.
Ehlers, Gizer, Gilder, and Yehuda (2013)	Alcohol, marijuana, stimulant, and nicotine dependence were significantly associated with increased odds of PTSD diagnosis and having experienced an injury/assault. Alcohol, marijuana, and stimulant dependence were significantly related to witnessing a traumatic event. Alcohol and stimulant dependence were significantly related to experiencing sexual abuse and being victim of a crime. Marijuana and stimulant dependence were significantly related to having experienced a natural disaster.
Emerson et al. (2017)	Lifetime PTSD diagnosis was significantly related to past year AUD.
Gilder et al. (2013)	Substance dependence diagnosis was significantly associated with increased odds of PTSD diagnosis.
Koss et al. (2003)	Among men, experiencing physical abuse, neglect, or both physical and sexual abuse was associated with significantly increased odds of alcohol dependence. Among women, experiencing physical, sexual, or emotional abuse, neglect, out-of-home placement, or both sexual abuse and boarding school attendance increased odds of alcohol dependence.
Kunitz et al. (1998)	Participants who experienced physical abuse were at increased risk for alcohol dependence. Alcohol dependence was associated with increased risk for being involved in domestic violence as either the perpetrator or the victim.
LeMaster et al. (2002)	Stressful life events were significant predictors of cigarette use. Death and loss were significant predictors of smokeless tobacco use.
Libby et al. (2004)	Childhood physical abuse was significantly associated with increased odds of alcohol and drug dependence but was associated with increased odds of alcohol and drug abuse in one community in the sample. Lifetime PTSD diagnosis was significantly associated with increased odds of alcohol and drug abuse and dependence.
Lobo and Vaughan (2003)	Participants described using substances to self-medicate to manage “mental stress.” Using substances was also described as making people more vulnerable to being the victim of a crime, such as theft or “bodily attack.”
Loving (2014)	Participants who reported current drinking had a greater number of cumulative adverse childhood experiences than those who had never drank.
Lujan et al. (1989)	Family alcohol abuse was more commonly identified in medical records of children experiencing child abuse and neglect than for children not experiencing abuse and neglect and was most common in medical records of children experiencing neglect.
Matamonasa-Bennett (2015)	Participants described alcohol use as contributing to intimate partner violence perpetration.
Myhra and Wieling (2014)	Participants described intergenerational patterns of substance use related to trauma exposure. Participants described substance use as increasing risk for being in accidents, and that children witnessing violence is related to their substance use.
O’Connell et al. (2007)	Witnessing domestic violence and having someone close experience a trauma was associated with increased odds of alcohol use in one community in the sample. Experiencing sexual abuse, witnessing domestic violence, and witnessing another traumatic event was associated with increased likelihood of using marijuana and/or inhalants. Having someone close experience a trauma was associated with increased likelihood of other illicit substance use/
Onoye et al. (2009)	Postpartum women meeting criteria for full and subclinical PTSD were more likely to binge drink, but no differences were found regarding frequency of alcohol use or smoking.
Pearce et al. (2008)	History of sexual abuse was associated with increased odds of lifetime injection drug use.
Pearson et al. (2015)	PTSD diagnosis was associated with increased odds of binge drinking.
Piasecki et al. (1989)	Adolescents who experienced both abuse and neglect had the greatest drug use, followed by neglect only, neither, then abuse only. Adolescents who experienced both abuse and neglect had the highest frequency of inhalant and non-alcohol drug-related problems. Children who experienced neglect only had the lowest frequency of alcohol problems and highest frequency of polydrug problems.
Robin et al. (1997)	Childhood sexual abuse was associated with increased likelihood of meeting criteria for an alcohol-related disorder.
Robin et al. (1999)	Males who experienced out-of-home placement were more likely to be diagnosed with SUDs. Females who experienced out-of-home placement were more likely to be diagnosed with an AUD or SUD.
Ross et al. (2015)	Childhood sexual abuse, physical abuse, or attending a residential school was associated with increased risk of experiencing alcohol and drug use problems.
Sawchuk et al. (2012)	PTSD diagnosis was not significantly associated with odds of smokeless tobacco use.
Sawchuk et al. (2016)	PTSD diagnosis was more common among smokers compared to nonsmokers.
Saylors and Daliparthy (2005)	Of participants in substance use treatment, 85% reported physical abuse and 100% reported emotional abuse. Alcohol and drugs were described as being involved in traumatic experiences by 47% of participants who reported childhood physical abuse, 74% of participants who reported physical abuse in adulthood, and 100% of clients who reported sexual abuse.
Simoni et al. (2004)	Physical and sexual abuse were significantly related to injection drug use. Sexual assault by someone other than a partner was associated with more frequent heavy drinking, and sexual and/or physical assault by someone other than a partner was associated with increased risk for injection drug use.
Walters and Simoni (1999)	Sexual assault by someone other than a partner was associated with increased substance use.
Warne et al. (2017)	Greater adverse childhood experiences were positively associated with severe alcohol misuse and cigarette smoking.
Whitesell et al. (2007)	Experiencing stressful life events was significantly related to substance dependence symptoms.
Whitesell et al. (2009)	Early stressful life experiences were significantly related to early substance use and risk for SUD.
J. R. Williams (2018)	Adverse childhood experiences were positively associated with polysubstance use. For men, emotional abuse was associated with alcohol and polysubstance use, and parent substance use was associated with polysubstance use. For women, parent substance use was associated with alcohol use.
Yuan et al. (2013)	For men, out-of-home placement was associated with increased risk for current alcohol dependence. For women, being adopted was associated with decreased risk for past year binge or spree drinking.
Zahradnik et al. (2011)	PTSD symptoms were positively associated with alcohol misuse.
Historical trauma and lived trauma
Brockie et al. (2015)	All lived trauma types (except physical neglect) and historical loss were associated with increased risk of polydrug use.
K. L. Gonzales et al. (2018)	Participants described alcohol and other substance use as a consequence of historical trauma, and a source of lived trauma that is passed down intergenerationally.
Myhra et al. (2015)	Participants identified healing from trauma within families as an important part of reducing SUDs. Participants identified reconnecting with their culture as important to achieving and maintaining sobriety.
Soto et al. (2015)	Past-month smoking and experimental smoking were significantly associated with stressful life events and historical trauma. Historical trauma significantly mediated the effect of stressful life events on smoking behaviors.
Spence et al. (2014)	Trauma was not significantly associated with odds of having used marijuana.

Note. NR = not reported; N/A = not applicable; CAB = community advisory board; CBPR = community-based participatory research; IHS = Indian Health Service; AUD = alcohol use disorder; SUD = substance use disorder; PTSD = posttraumatic stress disorder

In qualitative studies, participants described historical trauma as contributing to current substance use in their communities (Skewes & Blume, 2019), including alcohol use specifically (Brown et al., 2016; K. L. Gonzales et al., 2018; Trinidad et al., 2020). Participants reported that substance use resulted from pain related to loss of cultural identity (Skewes & Blume, 2019) and was a means by which individuals managed pain related to the intergenerational effects of colonization (Marsh et al., 2016; Myhra, 2011; Rothe, 2005). Of particular interest, Matamonasa-Bennett (2017) reported that alcohol was specifically a vehicle of colonization, and is both symbolic of colonization, precluding people from developing or maintaining their cultural identities, but also a way of protesting colonization. Participants in four studies described healing from substance use as necessary for reclaiming their heritage to counteract the effects of European colonization (Gone, 2009; Myhra, 2011; Myhra et al., 2015; Skewes & Blume, 2019). Only 3 of the 22 included studies did not find a significant association between historical trauma and substance use (Henderson et al., 1998; Luger, 2019; Spence et al., 2014).

Association Between Lived Trauma and Substance Use

Of the 46 studies that focused on the association between lived trauma and substance use among Indigenous populations, 39 (84.7%) found evidence of a significant association. Two studies found high rates of trauma exposure among individuals receiving substance use treatment (Deters et al., 2006; Saylors & Daliparthy, 2005). Eleven studies found a dose-response effect such that experiencing a greater number of traumatic events was associated with increased alcohol (Baldwin et al., 2011; Dick et al., 1993; Loving, 2014; Warne et al., 2017), cigarette (LeMaster et al., 2002; Soto et al., 2015; Warne et al., 2017), marijuana (Baldwin et al., 2011), and polysubstance use (Brockie et al., 2015; J. R. Williams, 2018), as well as substance dependence (Whitesell et al., 2007) and risk for alcohol use disorder (AUD; Boyd-Ball et al., 2006) and SUD (Whitesell et al., 2009). Experiencing physical abuse was associated with significantly increased risk for injection drug use (Simoni et al., 2004), DSM-IV alcohol and drug abuse and dependence (Koss et al., 2003; Kunitz et al., 1998; Libby et al., 2004), and alcohol and drug-related problems (Ross et al., 2015). A history of abuse, including sexual and emotional abuse/neglect and intimate partner/domestic violence, were associated with increased risk for substance use broadly (Piasecki et al., 1989; Walters & Simoni, 1999) including heavy drinking (Simoni et al., 2004), marijuana use (O’Connell et al., 2007), inhalant use (O’Connell et al., 2007), injection drug use (Pearce et al., 2008; Simoni et al., 2004), alcohol (Ehlers, Gizer, Gilder, & Yehuda, 2013; Koss et al., 2003; Kunitz et al., 1998; Robin et al., 1997) and stimulant dependence (Ehlers, Gizer, Gilder, & Yehuda, 2013), increased risk for alcohol and polysubstance use (J. R. Williams, 2018), and experiencing alcohol and drug-related problems (Ross et al., 2015). Out-of-home placements in childhood were associated with increased odds of alcohol dependence (Koss et al., 2003; Yuan et al., 2013), AUD and SUD diagnosis (Robin et al., 1999), and experiencing alcohol and drug-related problems (Ross et al., 2015). Conversely, Yuan et al. (2013) reported a negative association between trauma and substance use, finding that women who had been adopted outside of their Indigenous culture reported less past-year binge drinking.

Eleven studies focused specifically on the association between PTSD and substance use. Of these, seven found that PTSD diagnosis was associated with increased risk for AUD (Emerson et al., 2017), SUD (Beals et al., 2005; Gilder et al., 2013), alcohol use (Ehlers, Gizer, Gilder, & Yehuda, 2013; Libby et al., 2004; Onoye et al., 2009; Pearson et al., 2015), marijuana use (Ehlers, Gizer, Gilder, & Yehuda, 2013), stimulant use (Ehlers, Gizer, Gilder, & Yehuda, 2013), smoking and nicotine dependence (Dickerson et al., 2009; Ehlers, Gizer, Gilder, & Yehuda, 2013; Sawchuk et al., 2016), and general drug dependence (Libby et al., 2004). Others found that PTSD symptom severity was significantly associated with alcohol misuse (Zahradnik et al., 2011) and drug-related problems (Currie et al., 2015).

In qualitative studies, participants consistently described an association between lived trauma and substance use. Specifically, participants described children witnessing violence as a risk factor for substance use (Myhra & Wieling, 2014), and substance use as a means for self-medication to cope with trauma (Lobo & Vaughan, 2003), but also as a risk factor for experiencing future traumatic events (K. L. Gonzales et al., 2018; Lobo & Vaughan, 2003; Myhra & Wieling, 2014). Participants also reported that substance use contributed to risk for intimate partner violence (Burnette, 2016; Burnette & Renner, 2017; Matamonasa-Bennett, 2015). Finally, participants identified healing from trauma and reconnecting with culture as a necessary component of reducing SUDs and maintaining sobriety (Myhra et al., 2015).

Seven studies did not find evidence of a significant association between lived trauma and substance use among Indigenous individuals. Specifically, no significant associations were found between lived trauma and alcohol-related outcomes (Boyd-Ball et al., 2006; Dick et al., 1993), marijuana use (Spence et al., 2014), and drug-related problems (Currie et al., 2015). Regarding the association between PTSD and substance use, four studies did not find an association between PTSD and alcohol use (Onoye et al., 2009), smoking (Onoye et al., 2009), smokeless tobacco use (Sawchuk et al., 2012), and non-stimulant substance use (Deters et al., 2006).

Discussion

The present scoping review summarized the current body of literature on the association between trauma (historical and lived) and substance use among Indigenous populations. Increased understanding of this association is of utmost importance given known substance-related health disparities (Hawkins et al., 2004). Findings generally provide evidence to support a significant, positive link between substance use and both historical trauma (i.e., 86.4% of studies) and lived trauma (i.e., 84.7% of studies). These results support the notion that historical trauma may increase Indigenous peoples’ risk for experiencing lived trauma through the legacy of colonization and ongoing racism (K. L. Gonzales et al., 2018; Lobo & Vaughan, 2003; Myhra & Wieling, 2014), and underscore an overlap between historical and lived traumas for Indigenous communities. For example, residential boarding schools represent experiences of historical trauma given their explicit goal of furthering colonization and destruction of Indigenous culture (Bombay et al., 2014), but also represent lived traumas for many who were subjected to mental, physical, and sexual abuse and neglect in the boarding schools (Ross et al., 2015; Smith, 2004). Thus, findings of this review suggest that theories of trauma—including its co-occurrence with substance use—need to be expanded to include consideration of the additive effects of trauma across generations. Findings are also consistent with global literature regarding the impacts of colonization on the destruction of culture, and the subsequent negative impacts of those losses on well-being for Indigenous communities (Goldstein et al., 2018; Maple-Brown & Hampton, 2020; Okazaki et al., 2008; United Nations Department of Economic and Social Affairs, 2008). It is important to recognize the ways in which the legacy of colonialism has influenced the current state of global society and continues to contribute to the oppression of Indigenous peoples (Anastario et al., 2020; Steinmetz, et al., 2017). Additional work is needed to further understand how the intersection of historical and lived trauma dynamically influence substance use outcomes among Indigenous peoples in the United States, Canada, and globally, and to explore the role of government policies in perpetuating ongoing harm and oppression against Indigenous communities, furthering the deleterious effects of historical trauma.

Findings from the present review are well aligned with previous evidence suggesting a robust association between trauma and substance use among Indigenous individuals. Our findings suggest that, despite vast heterogeneity of experiences among Indigenous communities, there is a significant association between trauma and substance use across many different tribes/bands and settings (e.g., reservation/reserve, rural, urban). Acts of oppression by European-implemented governments stemming from colonization stripped away traditional ways of coping with emotional distress by banning and criminalizing traditional ways of healing (Brave Heart, 1998). This lack of traditional coping strategies, coupled with the emotional after-effects of mass cumulative trauma (e.g., depression, posttraumatic stress), likely left Indigenous people vulnerable to developing maladaptive ways of coping. Thus, Indigenous populations may have begun using substances as a way of self-medicating to cope with trauma memories and related emotional pain (Brave Heart, 2003). At the family level, historical stressors, such as the forced removal of Indigenous children from their families to attend residential schools, resulted in impairment in culturally normative parenting practices, leading to lack of affection and involvement, harsh discipline, and lax or inconsistent supervision (Brave Heart, 1999); these family level factors have been linked to Indigenous individual’s substance use (Brave Heart, 2003; Hawkins et al., 2004). Moreover, increases in parental substance use stemming from changing norms and values have led to increase in substance use among Indigenous youth (Brave Heart, 2003). At the community level, historical trauma led to a breakdown of traditional culture. Weak cultural identity, lack of adherence to traditional values and behaviors, and poor spiritual foundations have been shown to be related to substance use among Indigenous populations (Brave Heart, 2003; Hawkins et al., 2004; Spillane et al., 2020a, 2021; Spillane & Smith, 2007). It is worth noting that, except for studies mentioning PTSD or trauma exposure broadly, all of the lived traumas included in the present review were related to maltreatment by others. This makes sense given that Indigenous individuals have been found to be at increased risk for interpersonal types of traumas, such as physical (Evans-Campbell et al., 2006) and sexual (Bachman et al., 2010; Kirk-Provencher et al., 2020) assault. An important direction for future research will be to examine the effect of non-interpersonal trauma types (e.g., car accidents, natural disaster) on substance use among Indigenous populations.

Some studies did not find an association between trauma and substance use among Indigenous individuals. It is possible that these discrepancies are related to differences in communities or measurement of substance use (i.e., substance use vs. misuse). The effects of colonization were not uniformly felt across tribal groups. Some groups were able to maintain their cultural practices and traditions and maintain their language; while experiencing the effects of colonization, their ability to maintain their culture may have served some protective effect. Indeed, Indigenous youth have identified engagement in cultural practices as a potential protective factor against substance use (Spillane et al., 2020a). Further exploration is needed to determine for whom and under what circumstances trauma and substance use are significantly associated with one another among Indigenous communities.

Findings of the present review have important implications for clinical practice. In multiple studies included in the present review, participants identified healing from trauma and reconnecting with culture as necessary components for reducing substance use. Reattachment to cultural values may be achieved through engagement in traditional cultural practices, such as prayer and ceremonies (e.g., smudging, sweats, talking circles), language learning, and storytelling (e.g., telling of legends specific to the culture). Engagement in such practices may aid in reversing the damage that has been done by historical trauma on cultural identity, belonging, and purpose, connecting Indigenous people to their pre-traumatic past, and limiting transmission of historical trauma across generations (Brave Heart, 1998,1999, 2003; Brave Heart et al., 2011; Brave Heart & DeBruyn, 1998; Gone, 2009; Grayshield et al., 2015; Nutton & Fast, 2015). Researchers have attributed substance-related health disparities to numerous factors including barriers to healthcare (Marrone, 2007). For example, individuals may experience communication (e.g., cultural values) and/or language barriers with healthcare providers, and often live in economically disadvantaged conditions and rural areas that further constrain access to health services for Indigenous populations (Marrone, 2007; Goldstein et al., 2018). Furthermore, North American healthcare is based on Western principles and diverges from the traditional healing practices and important spiritual factors valued by Indigenous populations (Marrone, 2007), which may further decrease the likelihood of Indigenous people seeking and trusting health care systems. This underscores the importance of developing interventions in collaboration with Indigenous communities that focus on Indigenous practices and values (Schick et al., 2021) rather than simply adapting interventions that were designed for non-Indigenous populations (e.g., Seeking Safety; Marsh et al., 2016).

Limitations require consideration when interpreting findings of the present review. First, most studies included in the present review were conducted in the United States, which may have stemmed from our search terms being somewhat U.S.-centric. There is a high degree of variability across Indigenous groups, both throughout North America and globally. Additionally, there are numerous Indigenous groups that were not well-represented (e.g., Native Hawaiians, Inuit, Métis peoples) in the studies included in the present review. Thus, more work is needed to rigorously examine the association of trauma and substance use in these populations using community-based research methods and based on community-guided and developed research questions. Indigenous peoples and communities are experts on what will be most relevant for themselves; thus, research approaches should prioritize the perspectives of these individuals. Second, as a follow-up to our work, future research should investigate non-published papers to address any potential file drawer effects, as we only included studies that appeared through database searching. Further, studies were only included if they explicitly referred to substance use, trauma, and Indigenous group keywords in the title or abstract. This was necessary to allow for feasibility of screening an extensive list of abstracts. However, it means that our review may have excluded findings from studies that labeled these constructs under different terms in the title or abstract, such as studies with a majority Indigenous sample but not noting it in the title or abstract, or perhaps studies referring to specific substances or tribes/bands.

Finally, an important limitation of the research summarized in the present review is that all papers made use of cross-sectional designs, which leaves an important remaining gap in our understanding of the directionality of the association between trauma and substance use. This finding is of concern given that the prevailing theories of this co-occurrence largely differ in the directionality posited for the causal effect. Thus, based on the current state of the literature, we are unable to ascertain whether the current literature indicates a temporal association in which substance use increases risk for trauma (i.e., the high-risk hypothesis; Chilcoat & Breslau, 1998), trauma increases risk for substance use (i.e., the self-medication hypothesis; Khantzian, 1997), or whether trauma and substance use might share common underlying risk factors (i.e., the shared vulnerability hypothesis; Norman et al., 2012). Prospective designs are needed to further understand the association between trauma and substance use among Indigenous populations.

Despite limitations, the current scoping review highlights important gaps in the literature and in theoretical conceptions of the link between trauma and substance use among Indigenous populations. Our findings provide support for an association between both lived and historical trauma and substance use and speaks to the need for theories regarding the association between trauma and substance use to incorporate historical and intergenerational trauma. Further, this review highlights the need for more robust examinations of the relations among lived and historical trauma and substance use. Such research will inform culturally-tailored trauma-informed interventions to subsequently reduce the burden of substance use-related harm experienced by Indigenous communities.

Biographies

Author Biographies

Nichea S. Spillane, Ph.D., is an Associate Professor in the Psychology Department at the University of Rhode Island and Adjunct Professor in the Department of Behavioral and Social Sciences at Brown University. Her research focuses on positive psychology, substance use, health disparities, and underserved populations, including Indigenous populations in North America.

Melissa R. Schick, Ph.D., is a NIDA-funded T32 postdoctoral fellow at the Yale School of Medicine Division of Prevention and Community Research. Her research focuses on the application of positive psychology principles to prevention and intervention programs targeting health risk behaviors in North American Indigenous populations, as well as the role of other facets of positive emotions, such as positive emotion dysregulation and avoidance of positive emotions.

Katelyn T. Kirk-Provencher, Ph.D., is a postdoctoral fellow in the University of Colorado Anschutz Medical Campus Department of Radiology. Her research focuses on substance use within the context of sexual violence, with a particular emphasis on examining the interaction of alcohol use and bystander intervention during sexual violence on college campuses.

Tessa Nalven, M.A., is a doctoral candidate in the Clinical Psychology Program at the University of Rhode Island. Her research focuses on health disparities in substance use, with a particular interest in protective factors for substance use in multiracial individuals and people from other minoritized racial/ethnic groups.

Silvi Goldstein, M.A., is a doctoral candidate in the Clinical Psychology Program at the University of Rhode Island. Her research focuses on substance use, multicultural factors, and community psychology, with specific interest in harm reduction interventions for substance use within underserved communities.

Michael Crawford, M.A., is a doctoral student in the Clinical Psychology Program at the University of Rhode Island. His research focuses holistically on mental health disparities, as well as education and mental health policy.

Nicole H. Weiss, Ph.D., is an Associate Professor in the Psychology Department at the University of Rhode Island. Her research focuses on the co-occurrence of posttraumatic stress disorder (PTSD) and substance use disorder (SUD). In particular, she utilizes ecological momentary assessment (EMA) to clarify the proximal role and temporal ordering of affective processes—most notably emotion dysregulation—in PTSD symptoms and substance use over time.