Trauma informed interventions: A systematic review

Abstract

Health inequities remain a public health concern. Chronic adversity such as discrimination or racism as trauma may perpetuate health inequities in marginalized populations. There is a growing body of the literature on trauma informed and culturally competent care as essential elements of promoting health equity, yet no prior review has systematically addressed trauma informed interventions. The purpose of this study was to appraise the types, setting, scope, and delivery of trauma informed interventions and associated outcomes.

About the Authors:

Hae-Ra Han

Roles Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Project administration, Resources, Supervision, Writing – original draft, Writing – review & editing

* E-mail: [email protected]

Affiliations School of Nursing, The Johns Hopkins University, Baltimore, Maryland, United States of America, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland, United States of America

ORCID logo https://orcid.org/0000-0002-9419-594X

Hailey N. Miller

Roles Formal analysis, Writing – original draft, Writing – review & editing

Affiliation: School of Nursing, Duke University, Durham, North Carolina, United States of America

Manka Nkimbeng

Roles Data curation, Writing – original draft, Writing – review & editing

Affiliation: School of Public Health, University of Minnesota, Minneapolis, Minnesota, United States of America

ORCID logo https://orcid.org/0000-0001-7414-921X

Chakra Budhathoki

Roles Formal analysis, Writing – review & editing

Affiliation: School of Nursing, The Johns Hopkins University, Baltimore, Maryland, United States of America

Tanya Mikhael

Roles Data curation, Writing – review & editing

Affiliation: School of Nursing, The Johns Hopkins University, Baltimore, Maryland, United States of America

Emerald Rivers

Roles Data curation, Writing – review & editing

Affiliation: School of Nursing, The Johns Hopkins University, Baltimore, Maryland, United States of America

ORCID logo https://orcid.org/0000-0002-5569-6709

Ja’Lynn Gray

Roles Data curation, Writing – review & editing

Affiliation: School of Nursing, The Johns Hopkins University, Baltimore, Maryland, United States of America

Kristen Trimble

Roles Data curation, Writing – review & editing

Affiliation: School of Nursing, Vanderbilt University, Nashville, Tennessee, United States of America

Sotera Chow

Roles Data curation, Writing – review & editing

Affiliation: Medstar Good Samaritan Hospital, Baltimore, Maryland, United States of America

Patty Wilson

Roles Data curation, Formal analysis, Writing – original draft, Writing – review & editing

Affiliation: School of Nursing, The Johns Hopkins University, Baltimore, Maryland, United States of America

Abstract

Background

Health inequities remain a public health concern. Chronic adversity such as discrimination or racism as trauma may perpetuate health inequities in marginalized populations. There is a growing body of the literature on trauma informed and culturally competent care as essential elements of promoting health equity, yet no prior review has systematically addressed trauma informed interventions. The purpose of this study was to appraise the types, setting, scope, and delivery of trauma informed interventions and associated outcomes.

Methods

We performed database searches— PubMed, Embase, CINAHL, SCOPUS and PsycINFO—to identify quantitative studies published in English before June 2019. Thirty-two unique studies with one companion article met the eligibility criteria.

Results

More than half of the 32 studies were randomized controlled trials (n = 19). Thirteen studies were conducted in the United States. Child abuse, domestic violence, or sexual assault were the most common types of trauma addressed (n = 16). While the interventions were largely focused on reducing symptoms of post-traumatic stress disorder (PTSD) (n = 23), depression (n = 16), or anxiety (n = 10), trauma informed interventions were mostly delivered in an outpatient setting (n = 20) by medical professionals (n = 21). Two most frequently used interventions were eye movement desensitization and reprocessing (n = 6) and cognitive behavioral therapy (n = 5). Intervention fidelity was addressed in 16 studies. Trauma informed interventions significantly reduced PTSD symptoms in 11 of 23 studies. Fifteen studies found improvements in three main psychological outcomes including PTSD symptoms (11 of 23), depression (9 of 16), and anxiety (5 of 10). Cognitive behavioral therapy consistently improved a wide range of outcomes including depression, anxiety, emotional dysregulation, interpersonal problems, and risky behaviors (n = 5).

Conclusions

There is inconsistent evidence to support trauma informed interventions as an effective approach for psychological outcomes. Future trauma informed intervention should be expanded in scope to address a wide range of trauma types such as racism and discrimination. Additionally, a wider range of trauma outcomes should be studied.

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Citation: Han H-R, Miller HN, Nkimbeng M, Budhathoki C, Mikhael T, Rivers E, et al. (2021) Trauma informed interventions: A systematic review. PLoS ONE 16(6): e0252747. https://doi.org/10.1371/journal.pone.0252747

Editor: Vedat Sar, Koc University School of Medicine, TURKEY

Received: July 1, 2020; Accepted: May 23, 2021; Published: June 22, 2021

Copyright: © 2021 Han et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: This is a systematic review. All relevant data were extracted from the published studies included in the review.

Funding: This study was supported, in part, by a grant from the Johns Hopkins Provost Discovery Award (HRH). Additional funding was received from the National Center for Advancing Translational Sciences (UL1TR003098, HRH), National Institute of Nursing Research (P30NR018093, HRH; T32NR012704, HM), National Institute on Aging (R01AG062649, HRH; F31AG057166, MN), Robert Wood Johnson Foundation Health Policy Research Scholar program (MN), and Substance Abuse and Mental Health Services Administration (5T06SM060559‐ 07, PW). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. There was no additional external funding received for this study.

Competing interests: The authors have declared that no competing interests exist.

Background

Despite the United States’ commitment to health equity, health inequities remain a pressing concern among some of the nation’s marginalized populations, such as racial/ethnic or gender minority populations. For example, according to the 2016 National Health and Nutrition Examination Survey (NHANES), 29.1% of Mexican Americans and 24.3% of African Americans with diabetes had hemoglobin A1C greater than 9% (the gold standard of glucose control with levels ≤ 7% deemed adequate), compared to 11% in non-Hispanic whites [1]. The 2016 survey also revealed that 40.9% and 41.5% of Mexican Americans and African Americans with hypertension, respectively, had their blood pressure under control, compared to 51.7% in non-Hispanic whites. In 2014, 83% of all new diagnoses of HIV infection in the United States occurred among gay, bisexual, and other men who have sex with men, with African American men having the highest rates [2].

Several factors have been discussed as root causes of health inequities. For example, Farmer et al. [3] noted structural violence—the disadvantage and suffering that stems from the creation and perpetuation of structures, policies and institutional practices that are innately unjust—as a major determinant of health inequities. According to Farmer et al., because systemic exclusion and disadvantage are built into everyday social patterns and institutional processes, structural violence creates the conditions which sustain the proliferation of health and social inequities. For example, a recent analysis [4] using a sample including 4,515 National Health and Nutrition Examination Survey participants between 35 and 64 years of age revealed that black men and women had fewer years of education, were less likely to have health insurance, and had higher allostatic load (i.e., accumulation of physiological perturbations as a result of repeated or chronic stressors such as daily racial discrimination) compared to white men (2.5 vs 2.1, p<.01) and women (2.6 vs 1.9, p<.01). In the analysis, allostatic load burden was associated with higher cardiovascular and diabetes-related mortality among blacks, independent of socioeconomic status and health behaviors.

Browne et al. [5] identified essential elements of promoting health equity in marginalized populations such as trauma-informed and culturally competent care. In particular, trauma-informed care is increasingly getting closer attention and has been studied in a variety of contexts such as addiction treatment [6–8] and inpatient psychiatric care [9]. While there is a growing body of the literature on trauma-informed care, no prior review has systematically addressed trauma-informed interventions; one published review of literature [10] limited its scope to trauma survivors in physical healthcare settings. As such, the purpose of this paper is to conduct a systematic review and synthesize evidence on trauma-informed interventions.

For the purpose of this paper, we defined trauma as physical and psychological experiences that are distressing, emotionally painful, and stressful and can result from “an event, series of events, or set of circumstances” such as a natural disaster, physical or sexual abuse, or chronic adversity (e.g., discrimination, racism, oppression, poverty) [11,12]. We aim to: 1) describe the types, setting, scope, and delivery of trauma informed interventions and 2) evaluate the study findings on outcomes in association with trauma informed interventions in order to identify gaps and areas for future research.

Methods

Five electronic databases—PubMed, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), SCOPUS and PsycINFO—were searched from the inception of the databases to identify relevant quantitative studies published in English. The initial literature search was conducted in January 2018 and updated in June 2019 using the same search strategy.

Review design

We conducted a systematic review of quantitative evidence to evaluate the effects of trauma informed interventions. Due to heterogeneity relative to study outcomes, designs, and statistical analyses approaches among the included studies, we qualitatively synthesized the study findings. Three trained research assistants extracted study data. Specifically, we used the PICO framework to extract and organize key study information. The PICO framework offers a structure to address the following questions for study evidence [13]: Patient problem or population (i.e., patient characteristics or condition); Intervention (type of intervention tested or implemented); Comparison or control (comparison treatment or control condition, if any), and Outcome (effects resulting from the intervention).

Eligibility

Inclusion criteria.

Articles were screened for their relevance to the purpose of the review. Articles were included in this review if the study was: about trauma informed approach (i.e., an approach to address the needs of people who have experienced trauma) or an aspect of this approach, published in English language and involved participants who were 18 years and older. Also, only quantitative studies conducted within a primary care or community setting were included.

Exclusion criteria.

Exclusion criteria were: studies in or with military populations, refugee or war-related trauma populations, studies with mental health experts and clinicians as research subjects or studies of incarcerated and inpatient populations. Conference abstracts that had limited information on study characteristics were also excluded.

Search strategy and selection of studies

Search strategy.

Following consultation with a health science librarian, peer-reviewed articles were searched in PubMed, Embase, CINAHL, SCOPUS and PsycINFO using MeSH and Boolean search techniques. Search terms included: "trauma focused" OR "trauma-focused" OR "trauma informed" OR "trauma-informed." We also searched for the term trauma within three words of informed or focus ((trauma W/3 informed) OR (trauma W/3 focused), or (traumaN3 (focused OR informed)). Detailed search terms for each database are provided in Appendix 1.

Study selection.

The initial electronic search yielded 7,760 references and the follow-up search yielded 5,207 which were all imported into the Covidence software for screening [14]. Screening of the references was conducted by 2 independent reviewers and disagreements were resolved through consensus. There were 4,103 duplicates removed from the imported articles and 8,864 studies were forwarded to the title and abstract screening stage. Eight thousand five hundred and twenty-one studies were excluded because they were irrelevant. Three hundred and forty-three abstracts were identified to be read fully. Following this, 311 articles were excluded for focusing on other psychological conditions (n = 120), were non-experimental studies (n = 78) and were in inpatient or incarcerated populations (n = 46). One additional companion article was identified during full text review. Therefore, thirty-three articles met the inclusion criteria and are reported in this review. Fig 1 provides details of the selection process and identifies the reasons why articles were excluded at each stage.

[Figure omitted. See PDF.]

Fig 1. PRISMA diagram of a review of trauma-informed interventions.

https://doi.org/10.1371/journal.pone.0252747.g001

Quality assessment

We used the Joanna Briggs Institute quality appraisal tools [15] for randomized controlled trials (RCTs), quasi-experimental studies, and retrospective studies to assess the rigor of each study included in this review. The Joanna Briggs Institute quality appraisal tools [15] include items asking about methodological elements that are critical to the rigor of each type of study designs. In particular, one of the items for RCTs addresses participant blinding to treatment assignment. Due to the nature of trauma-informed interventions included in our review, it was decided that participant blinding is not relevant and hence was removed from the appraisal list for RCTs. No studies were excluded on the basis of the quality assessment. The quality assessment process was conducted independently by two raters. Inter-rater agreement rates ranged from 56% to 100% with the resulting statistic indicating substantial agreement (average inter-rater agreement rate = 77%). Discrepancies between raters were resolved via inter-rater discussion.

Results

Overview of studies

Table 1 summarizes the main characteristics of the 32 unique studies included in the review, with one companion article [16] for a study which was later reported with a more thorough examination of findings [17] totaling 33 articles. More than half (n = 19) of the 32 studies were RCTs [17–35] whereas twelve studies were quasi-experimental [36–47] and one was retrospective study [48]. Thirteen studies were conducted in the U.S. [17–19,22,26,27,29,35,39–41,45,47]; five in the Netherlands [30,31,33,38,48]; three in Canada [23,25,46]; two in Australia [21,24]; two in the United Kingdom [36,44]; two in Sweden [42,43]; on study in Chile [20]; Iran [32]; Haiti [37]; South Africa [34]; and Germany [28]. Fourteen of the studies only included females in their sample [18,20,21,23–25,27,28,38–41,45,48]. The average sample size was 78 participants, with a range from 10 participants [38] to 297 participants [48]. Of the studies included, 67% had a sample size above 50 [18–22,26,29–34,36,37,39–42,46–48].

[Figure omitted. See PDF.]

Table 1. Characteristics of the studies included in the review.

https://doi.org/10.1371/journal.pone.0252747.t001

The studies included in this review recruited their study populations largely based on the type of trauma they were aiming to address, such as individuals that experienced interpersonal traumatic event such as child abuse, sexual assault, or domestic violence [16–18,20–22,24–26,35,40–43,45,46], individuals with substance abuse disorders [19,47,48], couples experiencing clinically significant marital issues [23], individuals with limb amputations [38], dental phobia [28], or fire service personnel suffering from post-traumatic stress disorder [44]. Trauma was self-reported in eight articles [16,17,20,22,26,34,35,47]. In contrast, nine studies clearly identified a measurement of trauma; the Trauma History Questionnaire [19,45], the Childhood Trauma Questionnaire [23,25], the Childhood Maltreatment Interview Schedule [23], the Revised Conflict Tactics Scale adapted for sex work [39], the Traumatic Events Screening Instrument for Adults [27], the Life Events Checklist [46], and the Adverse Childhood Experiences [18]. Two studies used a clinical tool (e.g. eye movement desensitization and reprocessing [38] and Diagnostic and Statistical Manual of Mental Disorders, 4th edition [41] to identify or diagnose trauma. Fifteen studies did not include direct measurements for trauma [21,24,28–33,36,37,40,42–44,48].

Quality ratings

Tables 2–4 shows final scores of quality assessment. Quality of the 32 unique studies included in this review varied across individual studies. Twelve of 19 RCTs included in the review were of high quality (i.e., 9 to 11) [17,18,20,21,24,26,28,29,31,33–35] and six were of medium quality (i.e., 5 to 8) [19,22,23,25,27,30]. One study scored 4 of 12 [32]. The low rating study [32] lacked relevant information to adequately score its methodological rigor. Most RCTs clearly described randomization, group equivalence at baseline, rates and reasons for attrition, study outcomes, and analysis. Blinding of outcomes assessors to treatment assignment was used and described in several RCTs [17,20,21,24,27,35], whereas blinding of those delivering treatment was discussed clearly in only one study [25]. The majority of the quasi-experimental studies were of high quality (i.e., 7 or higher), except two, which scored 2 of 9 [37] and 6 of 9 [39], respectively. Six of twelve quasi-experimental studies [36,41–44,47] had a comparison group to strengthen internal validity of causal inferences by comparing intervention and control groups. Some of these studies, however, noted differences in baseline assessments between groups [36,43,44]. Finally, one retrospective study [48] scored 11 of 11 and hence was rated as high quality.

[Figure omitted. See PDF.]

Table 2. Study quality ratings for randomized control trials.

https://doi.org/10.1371/journal.pone.0252747.t002

[Figure omitted. See PDF.]

Table 3. Study quality ratings for quasi-experimental studies.

https://doi.org/10.1371/journal.pone.0252747.t003

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Table 4. Study quality ratings for cohort study.

https://doi.org/10.1371/journal.pone.0252747.t004

Characteristics of trauma-informed interventions

Type of intervention.

Table 5 details the trauma informed intervention characteristics included in this review. The two most frequently used interventions were eye movement desensitization and reprocessing (EMDR) [28,30,31,33,36,38]—a multi-phase intervention using bilateral stimulation, such as left-to-right eyes movements or hand tapping, to desensitize individuals to a traumatic memory or image—and trauma-focused cognitive behavioral therapy or cognitive behavioral therapy (CBT) [26,27,32,46,48]—a psychological approach to introduce emotional regulation and coping strategies (e.g., deep muscle relaxation, yoga, thought discovery and breathing techniques) to deal with negative feelings and behaviors surrounding a trauma of interest [32,48]. The implementation of CBT varied on the trauma of interest. Other studies implemented interventions using general trauma focused therapy [22,43], emotion focused therapy [23,25], stress reduction programs [17], cognitive processing therapy [24], brief electric psychotherapy [31], present focused group therapy [26], compassion focused therapy [44], prolonged exposure [45], stress inoculation training [45], psychodynamic therapy [45], and visual schema displacement therapy [30]. A number of studies included more than one of these therapies [13,26,30,31,33,36,45].

[Figure omitted. See PDF.]

Table 5. Trauma-informed intervention characteristics.

https://doi.org/10.1371/journal.pone.0252747.t005

Setting, scope, and delivery of intervention.

Twenty of the interventions were identified to occur in an outpatient clinic/setting [19–21,24,25,27–29,31–34,36,39,40,42,43,46–48]. Four of the studies took place in a research lab or office [23,26,41,45], one study occurred in the community [17], and one study implemented therapy in three locations, two of which were outpatient and one of which was a residential treatment center [47]. Lastly, one study occurred in internally displaced people’s camps within a metropolitan area in Haiti [37]. The remaining studies did not identify a specific setting [22,35,38,44].

The interventions ranged in length and time, but most often occurred weekly. The longest intervention was done by Lundqvist and colleagues [43], which lasted a total length of 2-years and included 46 sessions. Several other studies included 20 sessions or more [18,22,23,25,26]. The interventions were most commonly delivered by medical professionals, including but not limited to: psychologists or psychiatrists, therapists, social workers, mental health clinicians and physicians [16,17,20–29,33,36,38,39,41,44–47]. The articles frequently noted that the interventionists were masters-level-prepared or higher in their profession [21,23,25–27,33,40,47]. In addition to standard education and licensure, many of the professionals implementing the interventions were required to obtain further training in the therapy of interest [23–25,27–30,33,36,38–40,46,47]. Two studies were identified to be delivered by lay persons [34,37].

Fidelity was addressed in 16 of the included articles [16,19,21,23,24,26–30,33–35,45–47]. The manner in which fidelity was addressed varied by study. Videotaping or audiotaping therapy sessions [21,23,24,28–30,33,35] were most common, followed by deploying regular supervision of the therapy sessions [21,23,27,29,33,46], using a training manual or intervention protocols [19,21,33,46], or having individuals unaffiliated with the study or blind to the intervention rate sessions [21,26,28,35]. Additionally, three articles utilized fidelity checks/checklists to ensure components of the intervention were addressed [16,30,47] or had patients and/or therapists rate therapy sessions [26,34,45]. Finally, one study had quality assurance worksheets completed after each session that were later reviewed by the study coordinator [34].

Effects of trauma-informed interventions

Trauma-informed interventions were tested to improve several psychological outcomes, such as post-traumatic stress disorder (PTSD), depression, and anxiety. The most frequently assessed psychological outcome was PTSD, which was examined in 23 out of the 32 studies [17,20–27,31,33,35–39,41,42,44–48]. Among the studies that assessed PTSD as an outcome, 11 found significant reductions in PTSD symptoms and severity following the trauma-informed intervention [17,20,21,24,26,28,34,42,45–47], however, one of these studies, which utilized outpatient psychoeducation, did not find significant differences in reduction between the intervention and control group [20]. Trauma-informed interventions that were associated with a significant reduction in PTSD were a mindfulness-based stress reduction program [16], two therapies using the Trauma Recovery and Empowerment Model (TREM) [47], CBT [26,46], EMDR [28], general trauma-focused therapy [42], psychodynamic therapy [45], stress inoculation therapy [45], present-focused therapy [26], and cognitive processing therapy [24]. In addition, an intervention designed to reduce stress and improve HIV care engagement improved PTSD symptoms; however, this intervention was not intended to treat PTSD [34].

Other commonly assessed psychological symptoms, including depression and anxiety, were examined in 16 [17–21,24–26,29,31,32,35,40,44,47,48] and 10 [21,24,25,28,29,35,36,44,47,48] studies, respectively. Among these, trauma-informed interventions were associated with decreased or improved depressive symptoms in 9 studies [17,18,20,21,24,32,35,47,48] and decreased or improved anxiety in 5 studies [21,28,35,47,48]. For example, Vitriol and colleagues found that outpatient psychoeducation resulted in improved depressive symptoms in women with severe depression and childhood trauma [20]. Similarly, Kelly and colleagues found that female survivors of interpersonal violence experienced a significantly greater reduction of depressive symptoms in the intervention group (mindfulness-based stress reduction) compared to the control group [16,17]. Other therapies that resulted in improved depressive symptoms were TREM [47], prolonged exposure therapy [21], CBT [32, 46], psychoeducational cognitive restructuring [35], and financial empowerment education [18]. Cognitive processing therapy similarly resulted in large reductions in depression symptoms, however this reduction was also observed in the control group [24]. The same studies showed that TREM [47], prolonged exposure therapy [21], CBT [48], and psychoeducational cognitive restructuring [35] were associated with improved anxiety. Lastly, in a separate study than the one highlighted above, EMDR was associated with improved anxiety [28].

A select number of the studies found associations between trauma-informed interventions and other psychological outcomes such as attachment anxiety, attachment avoidance, psychiatric symptoms or dental distress. For example, the trauma-informed mindfulness-based reduction program implemented by Kelly and colleagues was associated with a greater decrease in anxious attachment, measured by the Relationship Structures Questionnaire, compared to the waitlist group [17]. Similarly, Masin-Moyer and colleagues found that TREM and an attachment-informed TREM (ATREM) were associated with significant reductions in group attachment anxiety, group attachment avoidance, and psychological distress in women with a history of interpersonal trauma [47]. Additionally, individuals in an outpatient substance abuse treatment program, consisting of psychoeducational seminars and trauma-informed addiction treatment, experienced significantly better outcomes of psychiatric severity, measured by the Global Appraisal of Individual Needs scale, compared to a control treatment group [19]. Doering and colleagues found that EMDR, compared to the control group, was associated with significantly greater improvement in dental stress, anxiety and fear in patients with dental-phobia [28].

There was a series of interpersonal, emotional and behavioral outcomes assessed in the included studies. For example, adult females that were sexually abused in childhood experienced a significant improvement in social interaction and social adjustment after receiving trauma focused group therapy [43]. Similarly, Dalton and colleagues found that couples that received emotion focused therapy experienced a significant reduction in relationship distress [23] and MacIntosh and colleagues found that individuals that received CBT reported lower interpersonal problems post-treatment [46]. Trauma-based interventions were also associated with emotional outcomes. Visual schema displacement therapy and EMDR both were superior to the control treatment in reducing emotional disturbance and vividness of negative memories [30]. In a separate study, CBT was found to reduce levels of emotional dysregulation in individuals that experienced childhood sexual abuse [46]. Lastly, trauma-informed interventions were associated with behavioral outcomes, including HIV risk reduction [26], decreased days of alcohol use [27], and improvements in avoidance of client condom negotiations, frequency of sex trade under influence of drugs or alcohol, and use of intimate partner violence support [40]. Interventions that were associated with these behavioral outcomes included trauma focused and present focused group therapy [26], CBT [27], and a trauma-informed support, validation, and safety-promotion dialogue intervention [40].

Publication bias

We analyzed three sets of outcome variables for publication bias: PTSD, depression, and anxiety. Based on Begg and Mazumdar test, there was no evidence of publication bias for PTSD (z = 1.55, p = 0.121) and anxiety (z = 0.29, p = 0.769). However, there was some evidence of publication bias for depression (z = 5.19, p<.001). The statistically significant publication bias for depression appears to be mainly due to large effect sizes in Nixon [24] and Bowland [35].

Discussion

According to our database search, this is the first systematic review to critically appraise trauma-informed interventions using a comprehensive definition of trauma. In particular, our definition encompassed both physical and psychological experiences resulting from various circumstances including chronic adversity. Overall, there was inconsistent evidence to suggest trauma informed interventions in addressing psychological outcomes. We found that trauma-informed interventions were effective in improving PTSD [17,20,21,24,26,28,34,42,45–47] and anxiety [21,28,35,47,48] in less than half of the studies where these outcomes were included. We also found that depression was improved in less than about two thirds of the studies where the outcome was included [17,18,20,21,24,32,35,47,48]. Although limited in the number of published studies included this review, available evidence consistently supported trauma-informed interventions in addressing interpersonal [23,43,46], emotional [30,46], and behavioral outcomes [26,27,40].

Effective trauma informed intervention models used in the studies varied, encompassing CBT, EMDR, or other cognitively oriented approaches such as mindfulness exercises [16,24,26,28,32,35,45,46,48]. In particular, CBT was noted as an effective trauma informed intervention strategy which successfully led to improvements in a wide range of outcomes such as depression [32,48], anxiety [48], emotional dysregulation [46], interpersonal problems [23,46], and risky behaviors (e.g., days of alcohol use) [27]. While the majority of the studies included in the review were focused on interpersonal trauma such as child abuse, sexual assault, or domestic violence [16–18,20–22,24–26,35,40–43,45,46], growing evidence demonstrates perceived discrimination and racism as significant psychological trauma and as underlying factors in inflammatory-based chronic diseases such as cardiovascular disease or diabetes [4]. Future trauma informed interventions should consider a wide-spectrum of trauma types, such as racism and discrimination, by which racial/ethnic minorities are disproportionately affected from [49].

While the majority of the trauma informed interventions were delivered by specialized medical professionals trained in the therapy [16,17,20–29,33,36,38–41,44–47], several of the articles lacked full descriptions of interventionist training and fidelity monitoring [20,22,25,36,38–41,44]. Two studies were identified to be delivered by lay persons [34,37]. There is sufficient evidence to suggest that lay persons, upon training, can successfully cover a wide scope of work and produce the full impact of community-based intervention approaches [50]. Given such, there is a strong need for trauma informed intervention studies to clearly elaborate the contents and processes of lay person training such as competency evaluation and supervision to optimize the use of this approach.

There are methodological issues to be taken into consideration when interpreting the findings in this review. While twenty-three of 32 studies were of high quality [17,18,20,21,24,26,28,29,31,33–36,38,40–48], some studies lacked methodological rigor, which might have led to false negative results (no effects of trauma informed interventions). For example, about one-third (31%) had a sample size less than 50 [17,23–25,27,28,35,38,43,45]. In addition, half of the quasi-experimental studies [37–40,45,46] did not have a comparison group or when they had one, group differences were noted in baseline assessments [36,43,44]. In several studies, therapists took on both traditional treatment and research responsibilities (e.g., delivery of the intervention) [20,25,29,32,33,36,40,46,47], yet blinding of those delivering treatment was discussed clearly in only one study [25]. This dual role is likely to have led to the disclosure of group allocation, hence, threatening the internal validity of the results. Future studies should address these issues by calculating proper sample size a priori, using a comparison group, and concealing group assignments.

Review limitations

Several limitations of this review should be noted. First, by using narrowly defined search terms, it is possible that we did not extract all relevant articles in the existing literature. However, to avoid this, we conducted a systematic electronic search using a comprehensive list of MeSH terms, as well as similar keywords, with consultation from an experienced health science librarian. Additionally, we hand searched our reference collections, Second, the trauma informed interventions included in this review were implemented to predominantly address trauma related to sexual or physical abuse among women. Thus, our findings may not be applicable to trauma related to other types of incidence such as chronic adversity (e.g., racism or discrimination). Likewise, there were insufficient studies addressing a wider range of trauma impacts such as emotion regulation, dissociation, revictimization, non-suicidal self-injury or suicidal attempts, or post-traumatic growth. Future research is warranted to address these broader impacts of trauma. We included only articles written in English; therefore, we limited the generalizability of the findings concerning studies published in non-English languages. Finally, we used arbitrary cutoff scores to categorize studies as low, medium, and high quality (quality ratings of 0-4, 5-8, and 9+ for RCTs and 0-3, 4-6, 7+ for quasi-experimental studies, respectively). Using this approach, each quality-rating item was equally weighted. However, certain factors (e.g., randomization method) may contribute to the study quality more so than others.

Conclusions

Our review of 33 articles shows that there is inconsistent evidence to support trauma informed interventions as an effective intervention approach for psychological outcomes (e.g., PTSD, depression, and anxiety). With growing evidence in health disparities, adopting trauma informed approaches is a growing trend. Our findings suggest the need for more rigorous and continued evaluations of the trauma informed intervention approach and for a wide range of trauma types and populations.

Supporting information

S1 Checklist.

https://doi.org/10.1371/journal.pone.0252747.s001

(DOCX)

S1 Appendix. Search strategies.

https://doi.org/10.1371/journal.pone.0252747.s002

(DOCX)

Acknowledgments

We would like to express our appreciation to a medical librarian, Stella Seal for her assistance with article search. Both Kristen Trimble and Sotera Chow were students in the Masters Entry into Nursing program and Hailey Miller and Manka Nkimbeng were pre-doctoral fellows at The Johns Hopkins University when this work was initiated.

Citation: Han H-R, Miller HN, Nkimbeng M, Budhathoki C, Mikhael T, Rivers E, et al. (2021) Trauma informed interventions: A systematic review. PLoS ONE 16(6): e0252747. https://doi.org/10.1371/journal.pone.0252747

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