Abstract
Objectives. We examined the prevalence of trauma in 2 large American Indian communities in an attempt to describe demographic correlates and to compare findings with a representative sample of the US population.
Methods. We determined differences in exposure to each of 16 types of trauma among 3084 tribal members aged 15 to 57 years through structured interviews. We compared prevalence rates of trauma, by gender, across the 2 tribes and with a sample of the US general population. We used logistic regression analyses to examine the relationships of demographic correlates to trauma exposure.
Results. Lifetime exposure rates to at least 1 trauma (62.4%–67.2% among male participants, 66.2%–69.8% among female participants) fell at the upper limits of the range reported by other researchers. Unlike the US general population, female and male American Indians exhibited equivalent levels of overall trauma exposure. Members of both tribes more often witnessed traumatic events, experienced traumas to loved ones, and were victims of physical attacks than their counterparts in the overall US population.
Conclusions. American Indians live in adverse environments that place them at high risk for exposure to trauma and harmful health sequelae.
American Indians live in pervasively adverse social and physical environments that place them at higher risk than many other Americans of exposure to traumatic experiences.1,2 Rates of violent victimization of American Indians are more than twice as high as the national average.3–6 They also suffer motor vehicle mortalities at a rate 2 to 3 times that among Whites.7 Deaths due to hypothermia, drowning, falls, poisoning, and burns are considerably more common among American Indians than among other groups.8 However, the available evidence provides little insight into individual experiences of trauma or variations across communities. Understanding such factors is critical to calculating risks of psychiatric disorder and other health consequences and to planning for their prevention as well as treatment.
Our study represented the first systematic assessment of the prevalence of trauma exposure in American Indian communities, specifically tribal members living on or near several large US reservations. Data were collected as part of the American Indian Service Utilization, Psychiatric Epidemiology, Risk and Protective Factors Project (hereafter “the project”), the largest, most comprehensive study of its kind. Our goals were to (1) describe the nature and frequency of trauma in these 2 American Indian communities, (2) examine the demographic correlates of trauma, and (3) place these findings in a larger context via a comparison with the results of the National Comorbidity Survey (NCS), a large psychiatric epidemiological survey of the US population.
METHODS
Samples
Details of the project have been provided elsewhere.9 Participants were randomly selected from tribal rolls, which constitute the formal, legal definition of membership in federally recognized tribes. The populations of inference were enrolled members of a southwest tribe and 2 closely related northern plains tribes who lived on or within 20 miles (32 km) of their reservations. (In our work with American Indian groups, maintenance of community confidentiality is as important as individual confidentiality. Therefore, we use general cultural descriptors rather than specific tribal names.10,11)
The southwest and northern plains tribes assessed belong to different linguistic families, have different histories of migration, subscribe to different principles for reckoning kinship and residence, and have historically pursued different forms of subsistence. Yet, both tribes have many experiences in common with other American Indian groups. They share histories of colonization, including dramatic military resistance, externally imposed forms of governance, forced dietary changes, mandatory boarding school education, and active missionary movements. Unemployment is widespread. Both tribes also exhibit internal variability in acculturation, education, and income. Their selection provided an opportunity to account simultaneously for the diversity and common experiences in a population that is relatively small yet heterogeneous.
A stratified random sample design was used with 8 strata. These strata comprised male and female tribal members in 4 age groups (15–24, 25–34, 35–44, and 45–54 years) at the time of study initiation in 1997. Eligibility for participation was restricted to noninstitutionalized tribal members. A replicate strategy was used in which random groupings of names were drawn from the tribal rolls and released in sequence to allow location of these individuals and, if eligible, their recruitment into the study. An elaborate location procedure involved searches of public records and queries of family members and knowledgeable community “key informants”; study supervisors rather than interviewers made the final location determination.9 Overall, 46.5% and 39.5% of southwest and northern plains members were living on or near their respective reservations. Once located and deemed eligible, 73.7% of the southwest tribe and 76.8% of the northern plains tribe agreed to participate. Data collection took place between June 1997 and December 1999, and the total sample was composed of 3084 participants.
The NCS was based on a multistage area probability sample of noninstitutionalized civilians in the 48 coterminous states. The sample was stratified according to age (15–24, 25–34, 35–44, or 45–54 years) and gender. NCS fieldwork was carried out by the Survey Research Center at the University of Michigan’s Institute for Social Research between September 1990 and February 1992. Trained lay interviewers collected the data. The overall response rate was 82.5%, and there were a total of 8098 participants. The NCS has been described in greater detail elsewhere.12,13
Data Collection Procedures
Project staff and lay interviewers in each community were trained to collect the data, aided by laptop computer administration. Extensive quality control procedures verified that all of the location, recruitment, and interview procedures were conducted in a standardized, reliable manner. Further details on project instrumentation can be found at http://www.uchsc.edu/ai/ncaianmhr/presentresearch/superprj.htm.
The NCS was similarly rigorous in its implementation. Quality control procedures were exacting, and informed consent was obtained in the same manner as in the present project.
Measures
Respondents were asked about 16 possible traumatic events drawn from other major epidemiological studies. These were designed to include events commonly reported in most populations and to be consistent with stress-ors identified in the revised third edition and the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R and DSM-IV ).12,13 In the case of each trauma, we determined the frequency of exposure and ages of first, most recent, and worst exposures. Mirroring the literature,14 these 16 events were then aggregated into 5 categories: (1) noninterpersonal trauma (e.g., disaster, life-threatening accident), (2) interpersonal trauma (e.g., combat, rape, sexual abuse, physical assault/abuse), (3) witnessed trauma (e.g., seeing violence perpetrated upon others, observing a serious accident or disaster that resulted in harm or death to others but not oneself), (4) unwitnessed trauma to close other (e.g., life-threatening illness, rape, suicide of a family member or friend), and (5) other trauma (i.e., types of trauma not included in the preceding categories).
Respondents were grouped into the 4 age categories listed earlier. Education was categorized as less than high school, high school or high school equivalency, or some college (among those who had completed at least 1 year of college or vocational school). Poverty status was based on income level, household size, and US federal standards.15 Employment status was classified as working for pay, not working for pay, or student. Marital status was divided into 3 categories: married or living as married; separated, widowed, or divorced; and never married.
The NCS asked about lifetime occurrences of each of 12 types of trauma. Eleven questions addressed specific events and experiences listed as traumas in DSM-III-R. The twelfth question was an open-ended item addressing “any other terrible experience that most people never go through.” For comparative purposes, individual traumas included in the project items were recoded to parallel the broad categories reported in the NCS,12,16 resulting in 8 types of trauma: life-threatening accident, natural disaster, trauma to a loved one, physical attack, sexual assault other than rape, rape, combat exposure, and witnessing a traumatic event.
Analyses
SAS17 and SPSS18 were used in constructing variables. All inferential analyses were conducted in Stata19 through the use of sample weights that accounted for differential selection probabilities across all strata and for patterns of nonresponse.20 Gender- and tribe-specific estimates are presented. With Stata’s19 “svytab” procedure, Pearson χ2 values, corrected for the survey design and converted to F values, were used to determine instances in which significant differences existed across groups. We present post hoc analyses of specific differences in which nonoverlapping confidence intervals were used; as a result of our use of multiple comparisons, we discuss only those comparisons significant at P< .01.
We employed similar analytic procedures and assumptions in comparing trauma exposures among the southwest, northern plains, and US populations, with data for the latter derived from the NCS. With Stata’s19 “svylogit” procedure, logistic regression methods were used to investigate the demographic correlates of the trauma categories.
RESULTS
Table 1 ▶ depicts the demographic characteristics of the project samples. Substantially more female than male tribal members were interviewed in the southwest tribe, probably reflecting differential migration patterns in which men are more likely to pursue off-reservation employment. Individuals from the northern plains tribe were more likely to live in poverty than were those from the southwest tribe, although rates in both tribes were high. Female members of the southwest tribe were less likely to be separated, widowed, or divorced than their northern plains counterparts.
TABLE 1—
Description of Sample: American Indian Service Utilization, Psychiatric Epidemiology, Risk and Protective Factors Project
| Southwest | Northern Plains | |||||||
| Male (SM; n = 617) | Female (SF; n = 829) | Male (NM; n = 790) | Female (NF; n = 848) | |||||
| % (99% CI) | Differencea | % (99% CI) | Differencea | % (99% CI) | Differencea | % (99% CI) | Differencea | |
| Gender | 43.5 (42.6, 44.4) | SF, NM, NF | 56.5 (55.6, 57.4) | SM, NM, NF | 49.5 (48.8, 50.3) | SM, SF | 50.5 (49.7, 51.3) | SM, SF |
| Age, y | ||||||||
| 15–24 | 25.7 (23.8, 27.8) | NM | 23.6 (21.9, 25.4) | 22.1 (20.6, 23.6) | SM, NF | 26.3 (24.8, 27.8) | NM | |
| 25–34 | 26.2 (23.3, 29.2) | 26.6 (24.2, 29.2) | 29.6 (27.1, 32.2) | 29.0 (26.5, 31.6) | ||||
| 35–44 | 25.9 (22.9, 29.1) | 29.6 (27.0, 32.3) | 29.9 (27.3, 32.6) | 25.4 (23.0, 28.0) | ||||
| ≥45 | 22.2 (20.1, 24.5) | NM | 20.2 (18.4, 22.2) | 18.4 (16.9, 20.0) | SM | 19.3 (17.9, 20.8) | ||
| Education | ||||||||
| Less than 12 y | 29.2 (24.7, 34.2) | 27.4 (23.5, 31.7) | 24.8 (21.1, 28.9) | 27.9 (24.1, 32.1) | ||||
| High school or equivalent | 46.5 (41.2, 51.8) | 38.8 (34.5, 43.4) | NM | 53.6 (48.9, 58.3) | SF, NF | 41.3 (36.8, 46.0) | NM | |
| Some college | 24.3 (20.1, 29.1) | SF | 33.7 (29.6, 38.2) | SM, NM | 21.6 (17.9, 25.8) | SF, NF | 30.8 (26.6, 35.3) | NM |
| Living in poverty | 42.9 (37.5, 48.4) | NM, NF | 48.6 (43.9, 53.3) | NM, NF | 59.0 (53.9, 64.0) | SM, SF | 63.9 (59.0, 68.6) | SM, SF |
| Employment status | ||||||||
| Working for pay | 62.5 (57.4, 67.4) | NF | 58.9 (54.5, 63.2) | 62.6 (57.9, 67.1) | NF | 50.0 (45.5, 54.6) | SM, NM | |
| Student | 10.5 (7.9, 13.9) | 10.7 (8.4, 13.6) | 8.3 (6.3, 10.9) | NF | 15.0 (12.3, 18.3) | NM | ||
| Not working for payb | 27.0 (22.6, 31.9) | 30.4 (26.3, 34.7) | 29.1 (24.9, 33.7) | 34.9 (30.6, 40.0) | ||||
| Marital status | ||||||||
| Marriedc | 57.5 (52.4, 62.4) | 62.2 (57.8, 66.4) | NM | 49.0 (44.2, 53.8) | SF | 53.7 (49.1, 58.2) | ||
| Separated, widowed, divorced | 8.9 (6.5, 12.1) | NF | 10.9 (8.4, 13.9) | NF | 13.9 (10.9, 17.7) | 17.8 (14.6, 21.4) | SM, SF | |
| Never married | 33.6 (29.2, 38.4) | 27.0 (23.4, 30.9) | NM | 37.1 (32.8, 41.6) | SF, NF | 28.6 (24.9, 32.6) | NM | |
Note. CI = confidence interval. Sample sizes are unweighted.
aEntries denote significant pairwise comparisons (P < .01).
bIncludes homemaker, looking for work, unemployed, retired, permanently disabled, and other.
cIncludes living together as if married.
Table 2 ▶ shows prevalence estimates and standard errors of lifetime experiences of the 16 types of traumas as well as the categories created to classify the events. Male northern plains tribal members were most likely to have experienced noninterpersonal trauma, and female southwest tribal members were least likely. Female tribal members were more likely than male tribal members to have experienced interpersonal trauma. Specifically, they were more likely to report physical abuse, particularly by a spouse, which demonstrated the highest prevalence.
TABLE 2—
Lifetime Prevalence Rates of Traumatic Events, by Region and Gender
| Southwest | Northern Plains | |||||||
| Male. (SM; n = 574) | Female (SF; n = 775) | Male (NM; n = 756) | Female (NF; n = 824) | |||||
| % (99% CI) | Differencea | % (99% CI) | Differencea | % (99% CI) | Differencea | % (99% CI) | Differencea | |
| Noninterpersonal trauma | 25.2 (20.7, 30.2) | SF, NM | 16.1 (12.9, 19.8) | SM, NM, NF | 36.4 (31.8, 41.3) | SM, SF, NF | 24.8 (20.9, 29.2) | SF, NM |
| Victim of disaster (i.e., flood, tornado, fire, drought, explosion) | 10.8 (7.9, 14.7) | NM | 8.9 (6.6, 12.1) | NM | 18.6 (15.1, 22.8) | SM, SF | 14.4 (11.3, 18.1) | |
| Victim of life-threatening accident | 18.2 (14.3, 22.8) | SF, NM | 9.2 (6.8, 12.3) | SM, NM | 27.3 (23.1, 32.0) | SM, SF, NF | 15.2 (12.0, 18.9) | NM |
| Interpersonal trauma | 25.5 (21.1, 30.6) | SF, NF | 40.2 (35.7, 45.0) | SM, NM | 31.0 (26.6, 35.7) | SF, NF | 41.9 (37.3, 46.6) | SM, NM |
| Served in direct combat | 3.6 (2.1, 6.1) | SF, NF | 0.0b (0.0, 1.9b) | SM, NM | 5.4 (3.7, 7.8) | SF, NF | 0.2 (0.0, 0.9) | SM, NM |
| Raped | 2.4 (1.2, 4.7) | SF, NF | 12.8 (9.8, 16.4) | SM, NM | 1.4 (0.6, 3.3) | SF, NF | 14.4 (11.4, 18.1) | SM, NM |
| Molested | 2.6 (1.3, 5.1) | SF, NF | 8.0 (5.7, 11.0) | SM, NM | 1.6 (0.7, 3.7) | SF, NF | 7.6 (5.4, 10.6) | SM, NM |
| Physically abused/hurt by parent/caregiver | 6.5 (4.2, 9.8) | 7.6 (5.4, 10.7) | 6.0 (4.1, 8.7) | 10.8 (8.1, 14.1) | ||||
| Physically abused/hurt by spouse or boyfriend/girlfriend | 3.6 (2.0, 6.4) | SF, NM, NF | 28.9 (24.9, 33.4) | SM, NM | 9.2 (6.7, 12.5) | SM, SF, NF | 31.0 (26.8, 35.6) | SM, NM |
| Physically abused/hurt by someone other than spouse or boyfriend/girlfriend | 4.8 (2.9, 7.8) | 8.5 (6.2, 11.7) | 7.4 (5.3, 10.4) | 8.1 (5.8, 11.3) | ||||
| Robbed, mugged, physically attacked (not including sexual attacks) | 15.0 (11.5, 19.4) | SF, NF | 4.0 (2.5, 6.3) | SM, NM | 16.8 (13.4, 20.8) | SF, NF | 7.4 (5.2, 10.5) | SM, NM |
| Witness to trauma | 46.7 (41.3, 52.1) | 46.3 (41.6, 51.0) | 51.9 (47.0, 56.8) | 51.7 (46.9, 56.4) | ||||
| Witnessed violence between family members | 29.5 (24.8, 34.7) | NF | 37.8 (33.3, 42.5) | 33.3 (28.8, 38.1) | 41.7 (37.1, 46.5) | SM | ||
| Witnessed others raped, injured, or killed (other than situations already described) | 9.6 (6.8, 13.4) | 4.7 (3.0, 7.2) | NM | 11.5 (8.6, 15.2) | SF | 6.1 (4.1, 8.8) | ||
| Witnessed serious accident or disaster where someone was badly hurt or killed | 30.8 (26.0, 36.1) | SF | 18.4 (15.0, 22.4) | SM, NM | 37.1 (32.4, 42.0) | SF, NF | 23.9 (20.1, 28.2) | NM |
| Trauma to someone close | 30.3 (25.5, 35.6) | 30.6 (26.4, 35.2) | 31.0 (26.7, 35.7) | 38.5 (34.0, 43.3) | ||||
| Someone close in life-threatening situation | 17.1 (13.4, 21.7) | 13.3 (10.4, 16.9) | 18.0 (14.5, 22.1) | 16.2 (12.9, 20.0) | ||||
| Someone close raped/sexually abused | 7.5 (5.1, 11.0) | NF | 12.4 (9.5, 15.9) | 8.0 (5.7, 11.1) | NF | 17.3 (14.0, 21.3) | SM, NM | |
| Family member or someone close commited suicide | 12.7 (9.5, 16.8) | 14.0 (11.0, 17.6) | 15.3 (12.1, 19.3) | 18.6 (15.2, 22.5) | ||||
| Other traumatic experiences | 1.8 (0.8, 4.0) | 1.0 (0.4, 2.5) | 2.2 (1.1, 4.5) | 1.0 (0.4, 2.8) | ||||
| Any type of trauma | 62.4 (56.9, 67.5) | 66.2 (61.7, 70.5) | 67.2 (62.4, 71.6) | 69.8 (65.3, 73.9) | ||||
Note. CI = confidence interval. Sample sizes are unweighted.
aEntries denote significant pairwise comparisons (P < .01).
bNo Southwest female tribal members reported combat exposure. As a means of calculating confidence intervals, 1 case was temporarily assigned as having involved combat exposure.
Witnessed traumas were common in all groups. Female members of the northern plains tribe were more likely than men of the southwest tribe to have witnessed family violence. A third of the sample reported that someone close to them had experienced a trauma. Finally, lifetime experience of any trauma was high across both populations and genders, ranging from 62.4% for male southwest tribe members to 69.8% for female northern plains tribe members. No post hoc differences were found between tribe or gender groups in the case of any trauma.
Table 3 ▶ presents the demographic correlates of trauma categories. Gender, age, educational attainment, poverty, employment, and marital status were significant correlates. After control for other demographic variables, female tribal members remained more likely than male tribal members to have experienced interpersonal trauma; noninterpersonal trauma more often occurred among male participants. There were differences in the associations between age and traumatic exposures according to tribe: only older northern plains members reported experiencing more noninterpersonal and interpersonal traumas than their younger counterparts.
TABLE 3—
Results of Multivariate Analysis of Demographic Correlates of Trauma Categories, by Tribe
| Southwest | Northern Plains | |||||||||
| Any Trauma | Noninterpersonal Traumas | Interpersonal Traumas | Witnessed Traumas | Traumas Happened to Someone Close | Any Trauma | Noninterpersonal Traumas | Interpersonal Traumas | Witnessed Traumas | Traumas Happened to Someone Close | |
| OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | |
| Gender | ||||||||||
| Male | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| Female | 1.06 (0.83, 1.36) | 0.50*** (0.37, 0.67) | 1.88*** (1.45, 2.43) | 0.91 (0.72, 1.15) | 0.90 (0.70, 1.16) | 0.98 (0.76, 1.26) | 0.46*** (0.35, 0.60) | 1.58*** (1.24, 2.01) | 0.86 (0.68, 1.09) | 1.22 (0.96, 1.56) |
| Age, y | ||||||||||
| 15–24 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| 25–34 | 0.84 (0.57, 1.23) | 0.95 (0.59, 1.52) | 1.26 (0.85, 1.88) | 0.96 (0.67, 1.38) | 0.83 (0.56, 1.22) | 0.79 (0.55, 1.15) | 1.54* (1.02, 2.33) | 1.46* (1.02, 2.11) | 0.93 (0.66, 1.31) | 0.93 (0.65, 1.34) |
| 35–44 | 0.73 (0.49, 1.09) | 1.20 (0.75, 1.91) | 1.07 (0.72, 1.58) | 0.68* (0.47, 1.0) | 0.82 (0.55, 1.22) | 1.03 (0.68, 1.55) | 1.65* (1.07, 2.55) | 1.54* (1.04, 2.28) | 1.06 (0.73, 1.53) | 1.04 (0.71, 1.53) |
| ≥45 | 0.56** (0.38, 0.84) | 1.41 (0.89, 2.26) | 0.97 (0.64, 1.47) | 0.70 (0.48, 1.03) | 0.77 (0.51, 1.17) | 0.70 (0.46, 1.07) | 1.63* (1.05, 2.55) | 1.61* (1.08, 2.40) | 0.75 (0.51, 1.10) | 0.99 (0.66, 1.47) |
| Education | ||||||||||
| Less than 12 y | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| High school or equivalent | 1.75*** (1.29, 2.38) | 1.58* (1.05, 2.38) | 1.08 (0.78, 1.51) | 1.92*** (1.41, 2.62) | 1.80*** (1.28, 2.53) | 1.02 (0.75, 1.40) | 1.14 (0.80, 1.62) | 1.30 (0.94, 1.78) | 1.20 (0.89, 1.62) | 1.09 (0.79, 1.50) |
| Some college | 2.33*** (1.64, 3.33 | 2.76*** (1.79, 4.23) | 1.81*** (1.27, 2.59) | 2.50*** (1.78, 3.53) | 2.15*** (1.49, 3.11) | 2.15*** (1.45, 3.19) | 2.31*** (1.55, 3.43) | 2.08*** (1.44, 3.00) | 1.83*** (1.29, 2.60) | 1.97*** (1.37, 2.84) |
| Poverty statusa | ||||||||||
| Not living in poverty | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| Living in poverty | 0.69** (0.53, 0.89) | 0.84 (0.62, 1.14) | 0.88 (0.68, 1.16) | 0.71** (0.55, 0.91) | 0.73* (0.56, 0.95) | 0.90 (0.68, 1.20) | 0.97 (0.73, 1.28) | 1.18 (0.90, 1.54) | 0.96 (0.74, 1.24) | 0.89 (0.68, 1.16) |
| Employment status | ||||||||||
| Employed | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| Student | 0.97 (0.61, 1.52) | 0.92 (0.50, 1.68) | 0.68 (0.41, 1.12) | 0.94 (0.60, 1.47) | 1.56 (0.98, 2.47) | 0.88 (0.58, 1.36) | 1.42 (0.89, 2.29) | 0.94 (0.60, 1.45) | 1.08 (0.73, 1.60) | 1.17 (0.77, 1.78) |
| Not working for payb | 0.97 (0.73, 1.31) | 1.01 (0.71, 1.42) | 0.70* (0.52, 0.95) | 0.99 (0.75, 1.32) | 0.89 (0.66, 1.20) | 1.00 (0.75, 1.33) | 1.21 (0.91, 1.63) | 1.00 (0.76, 1.31) | 1.11 (0.86, 1.44) | 1.02 (0.78, 1.34) |
| Marital status | ||||||||||
| Marriedc | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| Separated, widowed, divorced | 1.30 (0.87, 1.96) | 1.15 (0.73, 1.81) | 1.94*** (1.33, 2.83) | 1.25 (0.85, 1.84) | 1.05 (0.69, 1.58) | 1.10 (0.75, 1.61) | 1.03 (0.73, 1.45) | 1.48* (1.07, 2.05) | 0.99 (0.72, 1.37) | 0.85 (0.61, 1.19) |
| Never married | 0.70* (0.51, 0.95) | 0.84 (0.59, 1.21) | 0.88 (0.63, 1.21) | 0.87 (0.65, 1.16) | 0.67* (0.49, 0.93) | 0.48*** (0.36, 0.64) | 0.58*** (0.42, 0.79) | 0.85 (0.64, 1.14) | 0.57*** (0.43, 0.76) | 0.67** (0.50, 0.90) |
Note. OR = odds ratio; CI = confidence interval.
aBecause of the categorical nature of the income item, poverty status was indeterminable for some participants; these participants were coded as not living in poverty.
bIncludes homemaker, looking for work, unemployed, retired, permanently disabled, and other.
cIncludes living together as if married.
* P < .05; **P < .01; ***P < .001.
Greater educational attainment was related to greater trauma exposure, especially among members of the southwest tribe. Similarly, when significant, poverty was associated with less trauma exposure; employment status exhibited little relationship with trauma exposure. In the southwest tribe, participants who were separated, widowed, or divorced had greater odds of experiencing interpersonal traumas than those who were married or who had never married.
Finally, Table 4 ▶ depicts gender-specific prevalence rates of trauma exposure for the southwest, northern plains, and US populations across the 8 categories previously reported in the NCS.13,16 Members of the southwest and northern plains tribes consistently reported more often witnessing traumatic events and traumas occurring to loved ones than did their US counterparts.
TABLE 4—
Comparison of Trauma Exposure in Samples: American Indian Service Utilization, Psychiatric Epidemiology, Risk and Protective Factors Project and National Comorbidity Survey (NCS)
| Southwest | Northern Plains | NCS | ||||||||||
| Male (SM; n = 574) | Female (SF; n = 775) | Male (NM; n = 756) | Female (NF; n = 824) | Male (UM; n = 2833) | Female (UF; n = 3042) | |||||||
| % (99% CI) | Differencea | % (99% CI) | Differencea | % (99% CI) | Differencea | % (99% CI) | Differencea | % (99% CI) | Differencea | % (99% CI) | Differencea | |
| Witnessing a traumatic event | 46.7 (41.3, 52.1) | UM, UF | 46.3 (41.6, 51.0) | UM, UF | 51.9 (47.0, 56.8) | UM, UF | 51.7 (46.9, 56.4) | UM, UF | 35.7 (32.6, 39.1) | SM, SF, NM, NF, UF | 16.0 (13.9, 18.4) | SM, SF, NM, NF, UM |
| Life-threatening accident | 18.2 (14.3, 22.8) | SF, NM, UM | 9.2 (6.8, 12.3) | SM, NM, UM | 27.3 (23.1, 32.0) | SF, SM, NF, UF | 15.2 (12.0, 18.9) | NM, UM | 26.1 (23.2, 29.2) | SM, SF, NF, UF | 13.6 (11.5, 16.1) | NM, UM |
| Natural disaster | 10.8 (7.9, 14.7) | NM, UM | 8.9 (6.6, 12.1) | NM, UM, UF | 18.6 (15.1, 22.8) | SM, SF | 14.4 (11.3, 18.1) | 18.5 (15.9, 21.3) | SM, SF | 15.0 (12.8, 17.5) | SF | |
| Trauma occurred to loved one | 30.3 (25.5, 35.6) | UM, UF | 30.6 (26.4, 35.2) | UM, UF | 31.0 (26.7, 35.7) | UM, UF | 38.5 (34.0, 43.3) | UM, UF | 12.3 (10.2, 14.8) | SM, SF, NM, NF | 15.0 (12.9, 17.5) | SM, SF, NM, NF |
| Physical attack | 22.7 (18.5, 27.6) | SF, NF, UM, UF | 36.0 (31.6, 40.6) | SM, UM, UF | 27.1 (23.0, 31.7) | NF, UM, UF | 39.5 (35.0, 44.2) | SM, NM, UM, UF | 15.0 (12.7, 17.6) | SM, SF, NM, NF | 11.4 (9.6, 13.5) | SM, SF, NM, NF |
| Sexual assault other than rape | 2.6 (1.3, 5.1) | SF, NF, UF | 8.0 (5.7, 11.0) | SM, NM, UM, UF | 1.6 (0.7, 3.7) | SF, NF, UF | 7.6 (5.4, 10.6) | SM, NM, UM, UF | 2.8 (2.0, 4.1) | SF, NF, UF | 14.0 (11.9, 16.5) | SM, SF, NM, NF, UM |
| Rape | 2.4 (1.2, 4.7) | SF, NF, UF | 12.8 (9.8, 16.4) | SM, NM, UM | 1.4 (0.6, 3.3) | SF, NF, UF | 14.4 (11.4, 18.1) | SM, NM, UM | 0.8 (0.4, 1.6) | SF, NF, UF | 10.4 (8.5, 12.8) | SM, NM, UM |
| Combat exposure in war | 3.6 (2.1, 6.1) | SF, NF, UF | 0.0b (0.0, 1.9b) | SM, NM, UM | 5.4 (3.7, 7.8) | SF, NF, UF | 0.2 (0.0, 0.9) | SM, NM, UM | 6.2 (4.7, 8.2) | SF, NF, UF | 0.0c (0.0, 0.1c) | SM, NM, UM |
| Any type of trauma | 62.4 (56.9, 67.5) | UF | 66.2 (61.7, 70.5) | UF | 67.2 (62.4, 71.6) | UF | 69.8 (65.3, 73.9) | UF | 63.3 (60.0, 66.5) | UF | 53.5 (50.3, 56.7) | SM, SF,NM, NF, UM |
Note. CI = confidence interval; UM = US males in NCS; UF = US females in NCS. Sample sizes are unweighted.
aEntries denote significant pairwise comparisons (P < .01).
bNo SW females reported combat exposure. As a means of calculating confidence intervals, one case was temporarily assigned as having involved combat exposure.
cOne NCS female reported combat exposure (weighted prevalence of 0.0082%); therefore, no adjustments were necessary to calculate confidence intervals.
Also, male and female members of both tribes were more likely than their counterparts in the overall US population to have experienced physical attacks. Whereas no difference was found in the NCS in terms of rates of physical attacks among men and women, the female members of the southwest and northern plains tribes more often reported being victims of physical attacks than did male tribal members. In addition, men of the northern plains tribe and US men more frequently suffered life-threatening accidents than men of the southwest tribe. Overall, men reported greater involvement in life-threatening accidents than women.
Exposure to natural disasters was similarly high among members of the northern plains and US populations, with no observable gender differences. However, male southwest tribal members reported far less exposure to disasters than either their northern plains or US counterparts; likewise, female southwest tribal members reported significantly less exposure to disasters than male northern plains tribal members or US men and women overall.
Regardless of ethnicity, reports of both sexual assault other than rape and rape itself were consistently higher among women than men. There were no female tribal differences in terms of either form of sexual assault, and there were no population differences among women with respect to rape. However, US women as a whole were more likely than women from either tribe to report sexual assault other than rape.
In addition, combat exposure consistently differed between men and women across the populations. Finally, regardless of type of trauma, US women as a whole significantly less often reported experiencing any trauma than the other female and male groups in these studies.
DISCUSSION
Our study provides the first community-based estimates of trauma exposure among American Indian populations residing in 2 large rural reservations. Lifetime rates of exposure to at least 1 traumatic event ranged from 62.4% to 69.8%. The NCS13 estimated the lifetime prevalence of exposure to any trauma among US men and women at 60.7% and 51.2%, respectively. Its recent international analogue, the Australian National Mental Health Survey,21 in which methods akin to the NCS were used to interview more than 10 500 people 18 years or older drawn from a national probability sample of households, reported remarkably similar lifetime rates: 64.6% for men and 49.5% for women. The findings of the present project were comparable for men but vastly different for women, who reported equivalent trauma exposure to men. The only other published study of prevalence of trauma among American Indians, albeit based on a family linkage design, corroborates our finding.22 Thus, one of the most consistent observations in studies of traumatic exposure, the gender difference in exposure,23–28 was not evident here.
Knowledge of ethnic variations in trauma exposure is particularly sketchy and often contradictory. Norris’s study27 of a community-based sample of 1000 adults drawn from the southeastern United States showed that Whites are at higher risk than African Americans for lifetime trauma exposure, notably in regard to robbery, physical assault, tragic death, and natural disaster. In the 1996 Detroit Area Survey of Trauma (DAST), non-Whites exhibited a 2-fold higher risk than Whites for lifetime exposure to assaultive violence.26 Participants in the present project—both male and female members of the southwest and northern plains—much more frequently witnessed a traumatic event, experienced trauma to loved ones, and were victims of physical attacks than their US counterparts in the NCS.
The reasons for such differences may reside in the argument that aggressive acts become more serious and more often result in injury when assailants have been drinking than when they are sober. Analyses of 1992–1993 National Crime Victimization Survey data29 have revealed that alcohol escalates the likelihood of physical assault and injury during interpersonal conflict. An equally provocative possibility follows from the thesis that cultural norms that legitimize fighting among group members who drink heavily contribute to higher levels of violence.30 Both observations are important in light of the widespread presence of alcohol in many American Indian communities, the associated consumption patterns, and the violent consequences that often ensue.31 Analyses are under way with project data that will allow us to examine the potential association between trauma exposure—specifically assaultive violence—and alcohol use, abuse, and dependence.
Age, educational level, and poverty have been implicated in increased risks of exposure to traumatic experiences.23,24 Norris27 observed that physical attacks and sexual assaults decreased with age. Breslau et al.26 found that exposure to all forms of trauma peaked between the ages of 16 and 20 years but noted important variations in the experience of specific types of trauma across the life span. For example, assaultive violence declined markedly after the age of 20 years and continued to do so in subsequent periods. Other types of trauma, notably, the sudden, unexpected death of a loved one, remained a frequent experience, peaking near 45 years of age.
With respect to trauma in general, neither project tribe evidenced a peak in exposure according to age; no differences emerged until the 45- to 54-year age period, when lifetime prevalence of trauma declined only among older southwest members. In the southwest tribe, age was unrelated to any specific type of trauma with 1 exception: those 35 to 44 years old were less likely to witness traumas. Among northern plains members, age was related to increased odds of noninterpersonal as well as interpersonal traumas; odds were higher among individuals 25 years or older.
The DAST revealed that lifetime prevalence of assaultive violence, equivalent here to interpersonal trauma, was associated with education level (less than college) and income level (lower income groups). In sharp contrast, among the present participants, college education was consistently related to increased exposure to each form of trauma as well as to the experience of any trauma. Furthermore, a high school education or equivalent was associated with increased exposure to all types of trauma with the exception of interpersonal traumas among southwest tribal members.
Employment status was not related to prevalence of trauma in general among the northern plains and southwest tribes or to specific types of trauma among members of the former. However, in the southwest community, those not working for pay experienced fewer interpersonal traumas. Surprisingly, poverty status also differed in its association with trauma exposure from that found in the DAST. Among the present respondents, poverty either bore no relationship to trauma prevalence rates or was associated with less frequent exposure.
Finally, marital status, which has not been previously examined in the literature with respect to trauma exposure, exhibited similar associations in both tribes. Individuals who were separated, widowed, or divorced were more likely to be exposed to interpersonal trauma. Tribal members who had never married were far less likely to have experienced any trauma; in particular, they reported less frequent exposure to noninterpersonal trauma (northern plains members only) and to traumas affecting loved ones (both tribes). Non-married members of the northern plains tribe also witnessed far fewer events than their married or separated/widowed counterparts.
Our findings in regard to education, employment, and poverty were unexpected because of their departure from those of the DAST, as well as previous studies conducted among American Indians. In her study of homicide among American Indians, Bachman4 found that both social disorganization and economic deprivation contributed to high levels of lethal violence in reservation communities. This same set of associations has been noted in regard to other problems among American Indians, such as suicide32–34 and alcohol abuse.31 Hence, we anticipated that, in this study, impoverishment and lower levels of education and employment would be linked to greater trauma exposure. That they were not is puzzling and deserves further consideration.
It may be that educational attainment, for example, introduces greater mobility, broadening one’s participation in social worlds beyond reservation life and thereby increasing the probability of exposure to adverse events. Then again, to the extent that one’s educational status is discordant from that of peers—and, in this case, a college education is an exception in these communities—it may focus frustration and interpersonal tensions, fostering the likelihood of conflict. Being unemployed and poor in tribal communities may limit the breadth of social interactions in which one engages outside of kith and kin, with a concomitant decrease in exposure to conflict likely to escalate to assaultive violence.
Our findings with respect to marital status are consistent with observations that separation is related to domestic discord35 and that widowhood is related to loss,36 increasing exposure to trauma in both cases. It is also clear that unmarried individuals, by virtue of their smaller interpersonal networks and reduced social obligations, are much less likely to experience adverse events than their married counterparts.37
In conclusion, in these 2 American Indian communities, rates of exposure to at least 1 trauma fell at the upper end of the wide range previously reported among other populations. Yet, in contrast to the general US population, female American Indians experienced a level of exposure equivalent to their male counterparts. In regard to specific traumas such as sexual assault and rape among women and combat among men, long-observed gender differences held true. Intertribal differences also emerged, notably with respect to life-threatening accidents and natural disasters among male northern plains tribal members in contrast to southwest tribal members. Both populations witnessed traumatic events, experienced traumas involving loved ones, and were victims of physical attacks more often than the US population as a whole.
Finally, other demographic factors such as education and poverty did not exhibit the same associations with trauma exposure among American Indians as those suggested for other populations. New insights also emerged regarding the relationships of employment and marital status to prevalence rates of trauma both in terms of specific events and in general; such relationships have not been examined previously in the broader literature.
Given our interest in possible tribe-specific variations in trauma, we conducted this work with tribally defined populations. The decision to focus on reservation-based populations was also driven by both substantive and practical considerations. Including urban/ suburban tribal members in the project sample was well beyond the study’s resources. Thus, our populations of inference are clear, although circumscribed.
This study of American Indians living on or near their reservations is the first, to our knowledge, to involve the use of a methodology shared with broader epidemiological studies to estimate prevalence rates of trauma and psychiatric problems. However, we aggregated the 16 traumatic events into the same 8 categories used by Kessler and colleagues.13,16 By querying participants about the occurrence of an increased number of traumatic events, we may have altered the demand set of the interview, thereby encouraging reports of more such events. However, given the variation in trauma prevalence rates among the southwest, northern plains, and US respondents, this possibility seems unlikely. Also, by forcing the income and household composition information into a single dichotomous variable, we may have obscured the relationships with trauma observed in previous studies suggesting that individuals in the lowest income groups are most exposed,24,26 rather than the reverse.
Much more remains to be discovered with respect to trauma and its potential contributions to the well-documented disparities in health status and care among American Indians. For example, alterations in central and autonomic nervous system function and hormonal dysregulation are associated with trauma,38,39 and these changes, in turn, increase the risk for cardiovascular disease.40–43 It may be that high rates of trauma exposure contribute to the increasing prevalence of cardiovascular disease among American Indian men and women, the leading cause of death among this population.44,45
Similarly, trauma is closely linked to pain,46–52 a relationship verified in our own work among native peoples.53 Pain affects help-seeking behavior, adherence to treatment recommendations, and speed of surgical recovery, all often compromised in American Indians. Then, too, the nature and frequency of trauma are strongly related to the risk of posttraumatic stress disorder, and this chronic and debilitating mental illness has widespread ramifications in regard to health and social functioning in American Indian communities.54,55 Clearly, trauma and its sequelae must figure more importantly in our efforts to understand and ameliorate the health disparities that plague this special population.
Acknowledgments
This study was supported by National Institute of Mental Health (grants R01 MH48174 and P01 MH42473). Analyses for and writing of the article also were partially supported by the National Center for Minority Health and Health Disparities (grant P60 MD000507), the Agency for Healthcare Research and Quality (grant P01 HS10854), and the National Institute on Drug Abuse (grant R01 DA17803).
The members of the AI-SUPERPFP (American Indian Service Utilization, Psychiatric Epidemiology, Risk and Protective Factors Project) Team are as follows: Cecelia K. Big Crow, Dedra Buchwald, Buck Chambers, Denise A. Dillard, Karen DuBray, Paula A. Espinoza, Candace M. Fleming, Ann Wilson Frederick, Diana Gurley, Shirlene M. Jim, Carol E. Kaufman, Ellen M. Keane, Denise Lee, Monica C. McNulty, Denise L. Middlebrook, Christina M. Mitchell, Laurie A. Moore, Tilda D. Nez, Ilena M. Norton, Douglas K. Novins, Heather D. Orton, Carlette J. Randall, Angela Sam, Michelle L. Christensen Sarche, James H. Shore, Sylvia G. Simpson, Paul Spicer, and Lorette L. Yazzie.
The American Indian Service Utilization, Psychiatric Epidemiology, Risk and Protective Factors Project would not have been possible without the significant contributions of many people. The following interviewers, computer/data management staff, and administrative staff supplied energy and enthusiasm for an often difficult job: Anna Barón, Antonita Begay, Amelia Begay, Cathy Bell, Phyllis Brewer, Nelson Chee, Mary Cook, Helen Curley, Mary Davenport, Rhonda Dick, Pearl Dull Knife, Geneva Emhoolah, Roslyn Green, Billie Greene, Jack Herman, Tamara Holmes, Shelly Hubing, Cameron Joe, Louise Joe, Cheryl Martin, Jeff Miller, Robert Moran, Natalie Murphy, Melissa Nixon, Ralph Roanhorse, Margo Schwab, Jennifer Settlemire, Donna Shangreaux, Matilda Shorty, Selena Simmons, Wileen Smith, Tina Standing Soldier, Jennifer Truel, Lori Trullinger, Arnold Tsinajinnie, Marvine Two Eagle, Jennifer Warren, Intriga Wounded Head, Dawn Wright, Jenny Yazzie, and Sheila Young.
We also acknowledge the contributions of the Methods Advisory Group: Margarita Alegria, Evelyn Bromet, Dedra Buchwald, Peter Guarnaccia, Steve Heeringa, Ron Kessler, R. Jay Turner, and William Vega. Finally, we thank the tribal members who so generously answered all of the questions asked of them.
Human Participant Protection The protocol for this study was reviewed and approved by the Colorado Multiple Institutional Review Board. Local authorities associated with the tribal communities reviewed and approved both the study and this article for publication. In addition to tribal approval, informed consent was obtained from all respondents; in the case of minors, consent from parents or guardians was first acquired.
Peer Reviewed
Contributors S. M. Manson and J. Beals conceived the study and supervised its implementation. S. M. Manson led the writing; J. Beals supervised the data analysis. S. A. Klein contributed to field work coordination, data entry, and analyses. C. D. Croy provided statistical support. All of the authors contributed to interpretation of the data and writing of the article.
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