Effects of trauma‐informed approaches in schools: A systematic review

Exposure to different types of trauma have been associated with varying types and complexity of adverse outcomes, including adverse effects on cognitive functioning, attention, memory, academic performance, and school‐related behaviors. Given the growing research on trauma and increased knowledge about the prevalence, consequences and costs associated with trauma, there have been increased efforts at the local, state and federal levels to make systems “trauma‐informed” (Lang, Campbell, & Vanerploeg, 2015). While the intent of creating trauma‐informed approaches in schools is a noble one, relatively little is known about the benefits, costs, and how trauma‐informed approaches are being defined and evaluated (Berliner & Kolko, 2016). Adopting a trauma‐informed approach in a complex system such as a school building or district is a time consuming and potentially costly endeavor and thus it is important to assess the effects of this approach to inform policy and practice. This aim of this review was to assess trauma‐informed approaches in schools on trauma symptoms/mental health, academic performance, behavior, and socioemotional functioning. Trauma‐informed approaches include programs, organizations, or systems that realize the impact of trauma, recognize the symptoms of trauma, respond by integrating knowledge about trauma policies and practices, and seeks to reduce retraumatization. At least two of the three key elements of a trauma‐informed approach must have been present: Workforce development, trauma‐focused services, and organizational environment and practices, which differ from trauma‐specific interventions designed to treat or otherwise address the impact/symptoms of trauma and facilitate healing.


| The review in brief
Despite growing support and increased rate of which traumainformed approaches are being promoted and implemented in schools, evidence to support this approach is lacking.

| What is this review about?
Exposure to different types of trauma have been associated with varying types and complexity of adverse outcomes, including adverse effects on cognitive functioning, attention, memory, academic performance, and school-related behaviors. Given the growing research on trauma and increased knowledge about the prevalence, consequences and costs associated with trauma, there have been increased efforts at the local, state and federal levels to make systems "trauma-informed" (Lang, Campbell, & Vanerploeg, 2015). While the intent of creating trauma-informed approaches in schools is a noble one, relatively little is known about the benefits, costs, and how trauma-informed approaches are being defined and evaluated (Berliner & Kolko, 2016).
Adopting a trauma-informed approach in a complex system such as a school building or district is a time consuming and potentially costly endeavor and thus it is important to assess the effects of this approach to inform policy and practice.
This aim of this review was to assess trauma-informed approaches in schools on trauma symptoms/mental health, academic performance, behavior, and socioemotional functioning.
Trauma-informed approaches include programs, organizations, or systems that realize the impact of trauma, recognize the symptoms of trauma, respond by integrating knowledge about trauma policies and practices, and seeks to reduce retraumatization. At least two of the three key elements of a trauma-informed approach must have been present: Workforce development, trauma-focused services, and organizational environment and practices, which differ from trauma-specific interventions designed to treat or otherwise address the impact/symptoms of trauma and facilitate healing.

What is the aim of this review?
This Campbell systematic review sought to examine the effects trauma-informed schools on trauma symptoms/ mental health, academic performance, behavior, and socioemotional functioning. Although we conducted a comprehensive search to find studies testing traumainformed approaches in schools, no studies met the inclusion criteria.

| What do the findings of this review mean?
Despite widespread support and growing adoption of trauma-informed approaches in schools across the globe, we found no studies to provide good evidence to suggest that this approach is effective in achieving the stated goals. Given the degree to which trauma-informed approaches are being adopted in schools across the US and other countries, it is important that the effects of these programs be assessed.
1.5 | How up-to-date is this review?
The review authors searched for studies June through September, 2017.

| Background
Exposure to different types of trauma have been associated with varying types and complexity of adverse outcomes, including adverse effects on cognitive functioning, attention, memory, academic performance, and school-related behaviors. Given the growing research on trauma and increased knowledge about the prevalence, consequences and costs associated with trauma, there have been increased efforts at the local, state and federal levels to make systems "trauma-informed" (Lang et al., 2015). Indeed, federal legislation has been proposed to advance trauma-informed practice, with approximately 49 bills introduced between 1973 and 2015 that explicitly mentioned trauma-informed practice, with more than half introduced in 2015 alone (Purtle & Lewis, 2017). The promotion and provision of trauma-informed approaches in school settings in particular is growing at a rapid rate across the United States. At least 17 states have implemented trauma-informed approaches at the school, district, and even state-wide levels . This rapid increase in the growth of traumainformed approaches in schools has been fueled by a number of local, state, and federal initiatives and increasing support by education related organizations. While the intent of creating trauma-informed approaches in schools is a noble one, relatively little is known about the benefits, costs, and how trauma-informed approaches are being defined and evaluated (Berliner & Kolko, 2016). Adopting a trauma-informed approach in a complex system such as a school building or district is a time consuming and potentially costly endeavor, and there is potential for harm; therefore, it is important to assess the effects of this approach to inform policy and practice.

| Objectives
The purpose of this review was to identify, describe and synthesize the evidence of effects of trauma-informed approaches in schools to provide guidance for policymakers and educators and to identify important gaps in the evidence base.

| Search methods
We conducted a search for published and unpublished studies using a comprehensive search that included nine electronic databases and searches of various research registers, gray literature sources, reference lists of prior reviews and relevant studies, and contacts with authors and researchers in the field of trauma and school-based intervention research.

| Selection criteria
Criteria for inclusion in the review included: 1. Must have used a randomized or quasi-experimental study design in which participants who received an intervention were compared with a wait-list, no treatment, treatment-as-usual or an alternative treatment comparison group.
2. Studies must have been conducted in a school setting serving PreK-12 (or equivalent) students.
3. Studies must have assessed effects of a trauma-informed approach, defined as a program, organization, or system that realizes the impact of trauma, recognizes the symptoms of trauma, responds by integrating knowledge about trauma policies and practices, and seeks to reduce retraumatization. At last two of the three key elements of a trauma-informed approach must have been present: Workforce development, trauma-focused services, and organizational environment and practices (Hanson & Lang, 2016). This approach is distinguished from trauma-specific interventions, which are specific interventions designed to treat or otherwise address the impact/symptoms of trauma and facilitate healing.

4.
Studies must have measured a student-level outcome related to trauma symptoms/mental health, academic performance, behavior, or socioemotional functioning. 5. We did not limit studies based on publication status, geographical location or language. We searched for studies that had been published in the last 10 years, as this is a relatively recent movement

| Data collection and analysis
One reviewer searched all sources and uploaded all potentially relevant citations to Covidence, a systematic review software, for further screening by two reviewers. Two reviewers then independently screened each of the full-text reports for eligibility using a screening instrument. Disagreements related to eligibility were discussed and resolved between the two reviewers. Data extraction and analysis was not possible due to no studies having met criteria for inclusion in the review.

| Results
A total of 9,102 references from all searches were imported to Covidence for screening. After removal of 1,929 duplicates, 7,173 titles/abstracts were screened, and 7,106 studies were excluded. The remaining 67 studies were assessed for full-text eligibility by two independent reviewers. All 67 studies were excluded: 49 were neither an randomized controlled trial (RCT) nor quasi-experimental design (QED); 12 did not examine effects of a trauma-informed approach; 5 examined only one aspect of a trauma-informed approach (only workforce OR organizational OR practice changes); one was not a school-based intervention. Some studies may have been excluded for multiple reasons; however, only the first (primary) reason for exclusion was recorded. See Figure 1 for flowchart of the search and selection process. A full list of excluded studies can be found in References to Excluded Studies.
No studies met criteria for inclusion in this review.

| Authors' conclusions
Trauma-informed approaches are being promoted and used across child-serving systems, and the number of states and school districts adopting trauma-informed approaches in schools is growing rapidly . While the premise of a traumainformed schools approach is a noble one, it is unclear as to whether the promise of this framework is actually delivering the types of systemic and programmatic changes intended, and if those changes are resulting in the outcomes the proponents of a trauma-informed approach in schools hoped for. The purpose of this systematic review was to find, describe, evaluate, and synthesize effects of trauma-informed approaches in schools to inform policy and practice. While there are a number of publications that describe trauma-informed approaches, advocate for the need for trauma-informed approaches, and discuss the potential benefits of adopting such an approach in schools, we found no rigorous evaluations through our extensive search process.
From this review, it seems like the most prudent action for school leaders, policymakers, and school mental health professionals to do would be to proceed with caution in their embrace of a trauma-informed approach as an overarching framework and begin evaluating these programs. We simply do not have the evidence (yet) to know if this approach works, and indeed, we also do not know if implementing trauma-informed approaches in schools could have unintended negative consequences for traumatized youth and school communities. We also do not have evidence of other potential costs in implementing this approach in schools, whether they be financial, academic, or other opportunity costs, and whether benefits outweigh the costs of implementing and maintaining this approach in schools.
That said, calling for caution in adopting a trauma-informed approach in schools does not preclude schools from continuing to implement evidence-informed programs that target trauma symptoms in youth, or that they should simply wait for the research to provide unequivocal answers. We do encourage healthy skepticism and evaluation by the schools who are adopting a trauma-informed approach and clear descriptions of what schools are doing. Currently, despite several theoretical and guidance documents, it is not clear exactly what schools are doing when they say they are using a trauma-informed approach. Not only do we need more research on the effects, but descriptive and qualitative research on what is actually being implemented would be a welcome addition to the empirical literature in this area. We suspect that schools may be calling what they are doing a trauma-informed approach, but what is actually being done from school to school or district to district may vary quite widely in the practice and implementation of this approach. Clearly, rigorous research is needed in assessing the effects of using a trauma-informed approach in schools and we encourage rigorously designed studies in this area. Evaluating complex interventions such as this is not easy and requires resources.
Drawing from research on multi-tiered approaches in schools could help inform research approaches to assess the effects (and costs) of trauma-informed approaches in schools.

| The problem, condition, or issue
Childhood trauma has been receiving increased attention and it is increasingly being recognized as a significant public health concern (Lang et al., 2015). Trauma exposure involves "actual or threatened death, serious injury, or sexual violence" that is either directly experienced or witnessed, learning that any traumatic experiences have happened to a loved one, or having repeated exposure to details of traumatic events (American Psychiatric Association, 2013, p. 271).
Prevalence estimates of trauma experienced in childhood or adolescence vary by type of traumatic event (e.g., physical abuse, neglect, sexual abuse, witnessing violence, natural disasters) and how and when the traumatic experience is measured, but can range between 4% and 71% (Finkelhor, Turner, Shattuck, & Hamby, 2015;McLaughlin et al., 2013;Saunders & Adams, 2014). Prevalence and also vary by sociopolitical context as some countries are affected by war and have much higher levels of trauma (Bosqui, Marshoud, & Shannon, 2017).
Exposure to traumatic events can disrupt brain development and can have immediate and lifelong adverse effects on social, emotional, and physical wellbeing, including deficits in executive functioning, developmental delays, behavioral health problems, difficulty regulating emotions and behavior, academic performance and IQ, school behavior problems, delinquency, substance abuse, and mental health and psychiatric disorders (Anda et al., 2006;Delaney-Black et al., 2002;DePrince, Weinzierl, & Combs, 2009;Flannery, Wester, & Singer, 2004;Lang et al., 2015;Lansford et al., 2002). In a systematic review specifically examining school-related outcomes of traumatic event exposure, Perfect, Turley, Carlson, Yohannan, and Gilles (2016) identified 44 studies that examined cognitive functioning, 34 that examined academic functioning, and 24 that examined socialemotional-behavioral functioning. Their findings suggest that youth who have experienced trauma are at significant risk for impairments across various cognitive functions, including IQ, memory, attention and language/verbal ability; poorer academic performance and school-related behaviors such as discipline, dropout and attendance; and higher rates of behavioral problems and internalizing symptoms. MAYNARD ET AL.

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Exposure to different types of trauma have been associated with varying types and complexity of adverse outcomes. Kira, Lewandowski, Somers, Yoon, and Chiodo (2012) study of African American and Iraqi refugee youth found that different types of trauma differentially impact different components of cognitive functioning, including perceptual reasoning, working memory, processing speed and verbal comprehension. In another study examining effects of different types of trauma, exposure to violence was found to be associated with depression, separation anxiety, and conduct problems, whereas exposure to noninterpersonal traumatic events was associated with phobic anxiety (Briggs-Gowan et al., 2010).
Moreover, there is some evidence that the effects of trauma are cumulative, thus youth who experience a greater number of traumatic events are more at risk for adverse outcomes and more complex symptoms through adulthood (Chartier, Walker, & Naimark, 2010;Cloitre et al., 2009;Hodges et al., 2013). Duke, Pettingell, McMorris, and Borowsky (2010) analyzed data from respondents to the 2007 Minnesota Student Survey (n = 136,549), and identified "a significant positive relationship between each adverse event and delinquent behaviors for girls and boys," (p. e782). The effects of cumulative trauma also go beyond frequency, as the type, severity, and duration of trauma has been shown to be important (e.g., childhood sexual abuse has been found to have a stronger association with negative adult outcomes than other forms of abuse and neglect; Bebbington et al., 2004;Bosqui et al., 2014). While exposure to traumatic or potentially traumatic experiences are associated with a range of short and long-term outcomes, there are multiple pathways through which trauma can impact various domains across the life course. Moreover, not all youth will experience the same traumatic events in the same way and not all youth will develop symptoms following a traumatic experience (Layne et al., 2009).
Given the growing research on trauma and increased knowledge about the prevalence, consequences and costs associated with trauma, there have been increased efforts at the local, state, and federal levels to make systems "trauma-informed" (Lang et al., 2015). In an effort to examine the extent to which federal legislation has been proposed to advance trauma-informed practice, Purtle and Lewis (2017)  Globally, there is understanding of the impact of trauma on children and the consequences for the school environment. For example, multiple systems in Australia (child welfare, disability support, human services, mental health, legal context) have identified the need for using a trauma-informed lens in practice. The Queensland, Australia educational system was particularly interested in ensuring that the educational and mental health needs were met for children living in out-of-home care and children with complex trauma histories and therefore looked to a trauma-informed framework as a possible intervention to meet these needs. Prompted by limited success in meeting the challenges schools in Australia face with students with serious behavior concerns, the Queensland University of Technology and the Department of Education in Queensland conducted a study to explore the understanding and need for trauma-aware schooling and identified the need for comprehensive training and support for school personnel (Howard, 2018).
In the United Kingdom, to improve the connection between mental health services and the education system, the Department for Education and National Health Service have conducted multiple surveys and pilot projects in attempts to provide greater school-wide approaches to promote mental health and wellbeing for children.
They have identified trauma, attachment, and post-traumatic stress as key areas where schools need guidance (Department of Health & Department for Education, 2017). In response to the publication of the Department of Education and National Health Service, organizations such as the Center for Mental Health responded, urging the Government to put forth the adequate resources to implement whole school approaches and not only invest in trauma-focused interventions, but to also address the underlying causes that contribute to children's mental health (Hughes, n.d.).
In areas of the world where there is conflict, emergency, and crisis, both children and adults see schools as places of refuge, learning, and paths to better futures. International organizations such as Save the Children have identified education as priority for children and they urge both national governments and humanitarian actors to ensure that children have access to schooling and to ensure schools are providing the appropriate mental health support (Save the Children, 2015). The United Nations Girls' Education Initiative in the East Asia Pacific Region, which aims to ensure that both boys and girls receive primary and secondary education, have identified the need for additional support services for those who have experienced trauma (Clark & Sawyer, 2014). With limited resources and surrounding conflict, the knowledge of what environment would best support children's learning may be understood, but the lack of resources may prevent schools from implementing trauma-informed approaches.

| The intervention
Trauma-informed approaches are being promoted and used across child-serving systems and constitute a relatively new approach to trauma care for children and youth being served within the child welfare, juvenile justice, mental health, and education systems. While trauma-specific interventions, such as Trauma-Focused Cognitive Behavioral Therapy, are well known and widely used to treat traumarelated symptoms and disorders in both adults and children, traumainformed approaches to care are distinct from trauma-specific interventions. However, what is essential to a "trauma-informed approach" has not always been clearly operationalized, and the approach and variations of the approach have been referred to in varying ways, for example, "trauma-informed care," "trauma-sensitive," "trauma-informed system" (Hanson & Lang, 2016). To date, there is no consensus on the use of these terms, which makes efforts to both implement and study trauma-informed approaches to care challenging.
While there is much confusion, overlap and misuse of the various terminologies in this rather nascent area of practice and research, we are drawing from SAMHSA and the NCTSN to define traumainformed approaches for the purpose of this review. Substance Abuse and Mental Health Services Administration (2014) defines trauma-informed approaches (which the agency uses interchangeably with "trauma-informed care") as incorporating "key trauma principles into the organizational culture" of the program, agency, or system (p. 9). A trauma-informed approach is thus more akin to a multi-tiered framework such as School-Wide Positive Behavioral Supports (Chafouleas, Johnson, Overstreet, & Santos, 2016), and is based on incorporating four key assumptions and six key principles, generalizable to any setting, that are infused across all levels of an organization rather than implementing a prescribed set of practices The National Child Traumatic Stress Network (n.d.b) adapts the model outlined by SAMHSA to a context specific to youth and families, and describes their model as a "trauma-informed child-and family-service system," in which: all parties involved recognize and respond to the impact of traumatic stress on those who have contact with the system, including children, caregivers, and service providers. Programs and agencies within such a system infuse and sustain trauma awareness, knowledge, and skills into their organizational cultures, practices, and policies. They act in collaboration with all those who are involved with the child, using the best available science, to facilitate and support the recovery and resiliency of the child and family.
In essence, a trauma-informed approach is not a standalone intervention that can be delivered in isolation, but rather a framework to guide systems. A trauma-informed approach can include trauma-specific interventions, but trauma-specific interventions alone are not seen as sufficient for achieving optimal outcomes or to influence service systems (Substance Abuse and Mental Health Services Administration, 2014). Hanson and Lang (2016) identify three core domains essential to trauma-informed care that they Examples of trauma-informed approaches implemented in schools HEARTS is a whole-school program developed by the University of California, San Francisco to promote school success for students who have been impacted by trauma . This whole-school approach used the response to intervention three-tier framework of universal, selected and targeted interventions and included supports at the system, adult (teacher/ staff) and student levels at each tier. Activities involved changes in school policies and school-wide practices; training, PD, and consultation for all school staff around trauma-sensitive practices and stress, burnout and secondary trauma; and use of evidence-informed universal, secondary and targeted trauma-informed interventions.
TRUST in Schools: Trauma, Understanding & Sensitive Teaching is an example of a trauma-informed school approach being piloted in Australia (Harris, n.d.). This program focuses on recognizing the impact of trauma on children across the whole school, a school executive that promotes trauma-sensitive policies and procedures in the school, supporting school staff in implementing sensitive practices and engaging families, carers, and school communities in understanding the need for a trauma-sensitive whole school approach.
Trauma-informed approaches are also used at the preschool level. A multiorganization collaboration implemented a traumainformed approach in head start programs in the Appalachian region of the US . This comprehensive, three-tier model involved the use of trained consultants in the classroom to provide three tiers of services.
The first tier was universal consultation, intended to build teacher capacity to deliver an evidence-based social-emotional

| How the intervention might work
One out of every four children attending school has been exposed to a traumatic event, which can impact school performance, impair learning, and cause physical and emotional distress (NCTSN, 2008).
Moreover, the majority of youth who have experienced trauma do not receive services, and those who are exposed to a potentially traumatic event do not necessarily need an intervention (Layne et al., 2009). Due to the relatively high rates of youth exposed to traumatic events and the negative impacts of those traumatic experiences on academic achievement and life course outcomes, schools represent a natural system in which to help prevent and reduce the adverse effects of trauma and more effectively engage students in the learning process . Trauma-informed schools adopt the trauma-informed approach to "create educational environments that are response to the needs of trauma-exposed youth through the implementation of effective practices and system-change strategies" (Overstreet & Chafouleas, 2016, p. 1). A trauma-informed approach in schools is designed to create a systematic model for schools to decrease the impact of trauma on students (Wiest-Stevenson, & Lee, 2016) and more appropriately address academic, behavioral and socioemotional problems by recognizing and responding to student behavior from a trauma-informed perspective. This is done through a multilevel approach intended to improve the school environment through implementing trauma-informed policies and procedures; increase the ability of school staff to recognize and more effectively respond to students through PD; and prevent, mitigate and reduce trauma-associated symptoms through evidence-informed practices, leading to improved student academic, behavioral, and socioemotional outcomes.
As described above, a trauma-informed approach involves strategies implemented at various levels in the school and includes workforce/PD, organizational change, and practice change using evidence-informed practices (Hanson & Lang, 2016).

| Workforce/PD
The workforce and PD component is intended to increase staff knowledge about the prevalence and effects of trauma and associated cognitive, behavioral, and socioemotional effects of trauma. In addition, PD is intended to increase staff's ability to recognize signs and symptoms of trauma and improve skills in appropriately responding to students exhibiting trauma symptoms so that staff can more effectively address student behavior and make appropriate referrals for more targeted services. For example, typical strategies school staff use when addressing disruptive behavior that focus on consequences for misbehavior can exacerbate problems with trauma victims and miss an opportunity to more effectively intervene. By being trained to use a trauma-informed lens, school staff can proactively prevent and deescalate problematic behaviors that would typically disrupt the classroom and student learning, improving the learning environment for the entire class, and positively impact students' behavior, socioemotional and academic outcomes (Lang et al., 2015). In addition, workforce development initiatives may also promote the recognition of and skills to cope with secondary stress and prevent burnout, which may occur in providers serving traumatized populations.

| Organizational environment and practices
Schools may implement any of the following policies and procedures to realize organizational changes that maximize learning and reduce incidences of both traumatization and retraumatization. Changes may include: Modifying disciplinary practices, which contextualize the notion of "accountability" within an understanding of common reactions to trauma, minimize disruption in education, and model respectful relationships; establishing protocols for communication among caregivers, the school, and community agencies; modifications to the school's physical environment to promote safety; and, fostering partnerships with and linkages to community health and mental health resources (Cole et al., 2009).

| Why it is important to do the review
Although one could argue about the necessity or value of schools adopting a trauma-informed approach, trauma-informed approaches are being promoted and used across child-serving systems, and the number of states and school districts adopting trauma-informed approaches in schools is growing rapidly . While the intent of creating trauma-informed approaches in schools is a noble one, there is relatively little known about the benefits, costs, and how trauma-informed approaches are being defined and evaluated (Berliner & Kolko, 2016). Indeed, it is unclear whether schools adopting a trauma-informed approach (i.e., being a "trauma-informed school") are effective in reducing trauma symptoms or affecting behavioral or academic outcomes, as the proponents of the movement propose. Adopting a trauma-informed approach in a complex system such as a school building or district is a time consuming and potentially costly endeavor and thus it is important to assess the effects of this approach to inform policy and practice. Also, from our cursory review of the literature, the description of the trauma-informed approaches being implemented in schools vary in terms of the types of strategies used in each of the three areas and the relative emphasis on the three areas (policy/ procedures, PD, and practices), thus it is important to conduct a systematic inventory and description of the trauma-informed approaches implemented in schools to more fully understand how this approach is being utilized in schools, and whether variations in the components impact outcomes.
To date, we have not located any systematic reviews specifically examining effects of trauma-informed approaches in schools. We have identified reviews that have examined trauma-specific interventions for adolescents (e.g., Black, Woodworth, Tremblay, & Carpenter, 2012;Cary & McMillen, 2012) and those that examine school-based interventions for specific trauma-related disorders, such as PTSD (e.g., Rolfsnes & Idsoe, 2011); however, these reviews are examining effects of trauma-specific interventions rather than trauma-informed approaches. By virtue of these studies' primary research questions and inclusion criteria, the scope of these reviews were not designed to examine effects of a trauma-informed approach in schools.

| OBJECTIVES
This purpose of this review was to identify, describe and synthesize the evidence of effects of trauma-informed approaches in schools to provide guidance for policymakers and educators and to identify important gaps in the evidence base.
Specifically, the research questions guiding this review include: 1. What evidence is available to examine the effectiveness of trauma-informed practices in schools?
2. What are the study, intervention, and participant characteristics of studies that have rigorously evaluated the effects of traumainformed schools?
3. What are the components of trauma-informed approaches being used in schools?

4.
What are the effects of trauma-informed schools on trauma symptoms, socioemotional outcomes, behavior, and academic outcomes?

5.
Are there certain components of trauma-informed approaches that are more effective than others?
6. What adverse outcomes are reported by authors?

| Criteria for considering studies for this review
A protocol for this review was published in the Campbell Collaboration Library (Maynard, Farina, & Dell, 2017).

| Types of studies
To be included in this review, studies must have used one of the following research designs: RCT or QED with a treatment and comparison group using a wait list control, no treatment, treatmentas-usual and alternative treatment control group; therefore, single group pre-post test studies will be excluded. We excluded studies in which the comparison group received an intervention that would meet criteria as a trauma-informed approach (defined below), but included studies in which comparison groups received an alternative treatment that did not meet that criteria (e.g., a comparison group receiving a standalone trauma intervention would be included). The type of comparison group used in each study was coded. Given the nascent nature of research in this area, we anticipate lower-quality quasi-experimental and experimental studies. Although higher quality designs provide higher quality evidence, we were interested in capturing the research that currently exists and describing the quality of that research to inform research development in this area. Therefore, we did not require that studies provide pretest data or make statistical adjustments; however, we planned to code study design and analysis elements and use these variables in sensitivity and moderator analyses if there were a sufficient number of studies.

| Types of participants
We included studies that examined effects of the intervention in a school setting serving students in preschool through 12th grades (or equivalent grade levels in other countries).

| Types of interventions
Substance Abuse and Mental Health Services Administration (2014) defines a trauma-informed approach as a program, organization, or system that realizes the impact of trauma, recognizes the symptoms of trauma, responds by integrating knowledge about trauma policies and practices, and seeks to reduce retraumatization. Three key elements of a trauma-informed approach include workforce development, trauma-focused services, and organizational environment and practices (Hanson & Lang, 2016). SAMHSA distinguishes between a trauma-informed approach from trauma-specific interventions, the latter which are specific interventions designed to treat or otherwise address the impact/symptoms of trauma and facilitate healing. We intended to examine the effects of trauma-informed approaches implemented in school settings, often referred to as trauma-informed schools.
We anticipated that there would be wide variation in the implementation of the trauma-informed approach used in schools and variability in the principles and practices adopted by schools. We believe that identifying and describing this variation will be a significant contribution to the literature as currently "traumainformed schools" is often discussed as if everyone agrees on what this means or that any effort to become a "trauma-informed school" will be equally meaningful and effective.
Therefore, we wanted to be able to discern between studies examining trauma-specific interventions and those that were attempting a more comprehensive trauma-informed approach while not being overly limiting. Thus, for the purposes of this review, the intervention was considered a trauma-informed school approach if at least two of the following three components were present: 1. Workforce/PD-components of the program are designed to increase knowledge and awareness of school staff on the impact, signs and symptoms of trauma, including secondary traumatization. PD did not necessarily have to be provided to all school staff in a school, but there must be some staff development component as part of the program.

Organizational change-may include school-wide policies and
procedures and/or strategies or practices intended to create a trauma-informed environment integrating the key principles of the trauma-informed approach.
3. Practice change and use of evidence-informed trauma practicesthe program must implement changes in practice behaviors across the school, including trauma-specific screening, prevention and/or intervention services.
We planned to code each of the components and describe whether studies included all three components, and if not, which components were included.

| Types of outcome measures
Primary Outcomes. Studies must have measured at least one of the following student-level outcomes: • Trauma symptoms/mental health outcomes (e.g., anxiety, depression, post-traumatic stress disorder) • Academic performance (e.g., standardized achievement tests, measures of content mastery, reading, grades) • Behavior (e.g., disciplinary referrals, aggression and other externalizing behaviors, time on task, compliance, attendance) • Socioemotional (e.g., stress, engagement, social skills, self-esteem, emotion regulation, grit) Measurement of above outcomes may have been conducted using standardized or unstandardized instruments using self-, parent-, or teacher-reported or researcher administered measures.
To be included in the meta-analysis, primary study authors must have reported enough information to calculate an effect size. If sufficient information to calculate an effect size was not provided, we planned to make every effort to contact primary study authors and request the necessary information.

Secondary outcomes
We anticipated study authors may measure additional outcomes at different levels (individual, classroom, school) and planned to report teacher outcomes and outcomes related to implementation (e.g., satisfaction, fidelity) if reported. We were also interested in reporting of adverse outcomes. For all outcomes that do not fit into one of the primary outcome categories as noted above, we planned to code the outcomes and categorize them post hoc for descriptive purposes. If there were a sufficient number of studies reporting the same outcomes, we planned to extract effect size data and conduct a meta-analysis.

| Duration of follow-up
We planned to include measurement points at posttest and all followup time points and synthesize outcomes across studies that reported similar follow-up time points (i.e., up to 3 months, 3-6 months, 6-12 months, >12 months) if there were more than two studies that report sufficient data.

| Types of settings
We included studies of interventions conducted in a preschool through 12th grade (or equivalent) school setting.

| Other criteria
We did not limit studies based on publication status, geographical location, or language. We searched for studies that had been published in the last 10 years, as this is a relatively recent movement.

| Search terms and keywords
We used combinations of terms related to the intervention, population, study design, and setting to search the electronic databases. Database-specific strategies were explored for each database, including the use of truncation and database-specific limiters and thesauri were consulted to employ more precise search strategies within each database. Below are examples of the types of terms we used. See Table 1 in Tables and Figures for  Academic Search Complete KW ("trauma-informed" OR "trauma-sensitive" OR "trauma services" OR trauma OR PTSD OR "post-traumatic stress disorder") AND ("elementary school" OR "primary school" OR "high school" OR "secondary school" OR "middle school" OR kindergarten OR "pre-kindergarten" OR child* OR youth OR adolescent OR school) AND (evaluation OR intervention OR treatment OR outcome OR program OR trial OR experiment OR "control group" OR "controlled trial" OR "quasi-experiment" OR random*) June 13, 2017 Database of Research on International Education ("trauma-informed" OR "trauma-sensitive" OR "trauma services" OR trauma OR PTSD OR "post-traumatic stress disorder") AND ("elementary school" OR "primary school" OR "high school" OR "secondary school" OR "middle school" OR kindergarten OR "pre-kindergarten" OR child* OR youth OR adolescent OR school) AND (evaluation OR intervention OR treatment OR outcome OR program OR trial OR experiment OR "control group" OR "controlled trial" OR "quasi-experiment" OR random*) June 13, 2017 Education Source KW ("trauma-informed" OR "trauma-sensitive" OR "trauma services" OR trauma OR PTSD OR "post-traumatic stress disorder") AND ("elementary school" OR "primary school" OR "high school" OR "secondary school" OR "middle school" OR kindergarten OR "pre-kindergarten" OR child* OR youth OR adolescent OR school) AND (evaluation OR intervention OR treatment OR outcome OR program OR trial OR experiment OR "control group" OR "controlled trial" OR "quasi-experiment" OR random*) June 13, 2017 ERIC SU ("trauma-informed" OR "trauma-sensitive" OR "trauma services" OR trauma OR PTSD OR "post-traumatic stress disorder") AND ("elementary school" OR "primary school" OR "high school" OR "secondary school" OR "middle school" OR kindergarten OR "pre-kindergarten" OR child* OR youth OR adolescent OR school) AND (evaluation OR intervention OR treatment OR outcome OR program OR trial OR experiment OR "control group" OR "controlled trial" OR "quasi-experiment" OR random*) June 13, 2017 MEDLINE ((trauma-informed or trauma-sensitive or trauma services or trauma or PTSD or post-traumatic stress disorder) and (elementary school or primary school or high school or secondary school or middle school or kindergarten or pre-kindergarten or child* or youth or adolescent or school) and (evaluation or intervention or treatment or outcome or program or trial or experiment or control group or controlled trial or quasi-experiment or random*)).hw.
June 13, 2017 ProQuest Dissertations and Theses diskw(("trauma-informed" OR "trauma-sensitive" OR "trauma services" OR trauma OR pood OR "post-traumatic stress disorder") AND ("elementary school" OR "primary school" OR "high school" OR "secondary school" OR "middle school" OR kindergarten OR "pre-kindergarten" OR child* OR youth OR adolescent OR school) AND (evaluation OR intervention OR treatment OR outcome OR program OR trial OR experiment OR "control group" OR "controlled trial" OR "quasi-experiment" OR random*)) June 14, 2017 PsycINFO ((trauma-informed or trauma-sensitive or trauma services or trauma or PTSD or posttraumatic stress disorder) and (elementary school or primary school or high school or secondary school or middle school or kindergarten or pre-kindergarten or child* or youth or adolescent or school) and (evaluation or intervention or treatment or outcome or program or trial or experiment or control group or controlled trial or quasi-experiment or random*)).sh June 14, 2017 Social Science Citation Index ("trauma-informed" OR "trauma-sensitive" OR "trauma services" OR trauma OR PTSD OR "post-traumatic stress disorder") AND ("elementary school" OR "primary school" OR "high school" OR "secondary school" OR "middle school" OR kindergarten OR "pre-kindergarten" OR child* OR youth OR adolescent OR school) AND (evaluation OR intervention OR treatment OR outcome OR program OR trial OR experiment OR "control group" OR "controlled trial" OR "quasi-experiment" OR random*) June 14, 2017 CINAHL SU ("trauma-informed" OR "trauma-sensitive" OR "trauma services" OR trauma OR PTSD OR "post-traumatic stress disorder") AND ("elementary school" OR "primary school" OR "high school" OR "secondary school" OR "middle school" OR kindergarten OR "pre-kindergarten" OR child* OR youth OR adolescent OR school) AND (evaluation OR intervention OR treatment OR outcome OR program OR trial OR experiment OR "control group" OR "controlled trial" OR "quasi-experiment" OR random*) June 14, 2017 2) Targeted population: "elementary school" OR "primary school" OR "high school" OR "secondary school" OR "middle school" OR

| Reference lists and contact with authors
The reference lists from prior reviews and studies retrieved for fulltext screening were reviewed for potential studies. We had planned to conduct forward citation searches for all included studies; however, no studies met inclusion criteria. We also emailed (or attempted to email) first/corresponding authors of all full-text reports screened for inclusion. Covidence identified disagreements which the two reviewers then resolved through discussion and consensus.

| Data extraction and management
No studies met inclusion criteria, thus data was not extracted from studies.

| Assessment of risk of bias in included studies
No studies met inclusion criteria, thus risk of bias was not assessed.

| Measures of treatment effect
No studies met inclusion criteria, thus no effect sizes were calculated. No studies met criteria for inclusion in this review.

| Risk of bias in included studies
No studies met inclusion criteria, thus no studies were assessed for risk of bias.

| Synthesis of results
No studies met inclusion criteria for this review, thus no synthesis was conducted. 7 | DISCUSSION

| Summary of main results
Trauma-informed approaches are being promoted and used across child-serving systems, and the number of states and school districts adopting trauma-informed approaches in schools in the US and other countries is growing rapidly

| AUTHORS' CONCLUSIONS
This empty review comes at an admittedly early stage in American schools' embrace of the trauma-informed approach. Many innovations in education start with a great deal of excitement and moral fervor that is often not matched by rigorous evaluation of the interventions or curriculum being implemented (Walker, 2004).
The trauma-informed approach appears to be no exception; despite the increasing adoption of trauma-informed approaches in schools, we found no rigorous evaluations of trauma-informed approaches in schools that might indicate whether or how this approach works to address the various impacts of trauma on young people, families, and educators. This review also could not provide any strong evidence to date of what the school-level impacts are (if any) of implementing this approach, such as improved academic and behavioral outcomes and reduced teacher burnout, raising concern about the possibility that the trauma-informed "movement" might collapse or fizzle without any solid evidence to support its goals, as so many other wellintentioned school mental health interventions have in the past (Kelly, Raines, Stone & Frey, 2010).
While we have noted in our review that there are individual programs with evidence to support their effectiveness as schoolbased interventions for students dealing with trauma, there appears to be an implication that those programs alone "count" as evidence that using a trauma-informed approach itself works in K-12 education. We have observed this in our own home areas, and in several of the excluded studies that claimed to be using an evidenceinformed approach, but were evaluating a specific program, like CBITS, SPARCS, and Bounce Back. These targeted prevention or intervention programs may be effective in reducing trauma symptoms, but do not constitute a trauma-informed approach as defined by SAMHSA. It is important that a clear definition of what constitutes a trauma-informed approach in schools be established and that schools, and evaluators, be clear in discerning between whether they are truly implementing a trauma-informed approach, or implementing an evidence-informed intervention to prevent or treat trauma. This review also points to the persistent problem of scale and diffusion of innovative practices in education and sheds some possible light on how this is playing out with the trauma-informed approach movement. It is unfortunately not uncommon for education innovations to be embraced and adopted on a relatively large scale prior to rigorous evidence demonstrating positive effects. Indeed, this is what happened with PBIS/RTI/MTSS. The public health prevention framework that first emerged in the early 1990s was codified into federal law in the late 1990s and early 2000s, and then over time slowly developed a strong evidence base to support their effectiveness in addressing academic, behavioral, and emotional problems for youth in K-12 schools (Bradshaw, Koth, Thornton, & Leaf, 2009;Bradshaw, Koth, Bevans, Ialongo, & Leaf, 2008;Horner & Sugai, 2015). Today it is estimated that the three-tier frameworks of PBIS/RTI/MTSS have been implemented in over 19,000 American schools, making them one of the most scaled-up educational interventions in American schools (Barrett, Eber, & Weist, 2013).
The trauma-informed approach may very well follow this same trajectory, but we encourage greater attention to promoting rigorous evaluation of trauma-informed approaches in schools sooner rather than later.
In considering the issue of scaling up an innovative strategy like the trauma-informed approach, we can draw from Clark & Dede's scaling framework for educational innovations (2009). However, of the five components of Clark & Dede's scaling framework for educational innovations, which includes depth/effectiveness of the innovation followed by the innovation's sustainability, spread, adoption, and evolution/further adaptation, the only one that appears to be active with the trauma-informed approach is the "spread" of the trauma-informed framework; however, loosely it appears to be presently defined. In just a short period of time, the trauma-informed approach has already begun to "spread" into American K-12 education at a rapid clip. This rapid spread has the potential to quickly become another example of an education trend that falters without evidence to sustain them (Baker, 2007;Dearing et al., 2015). This empty review demonstrates that the other components of Clark & Dede's scaling framework, largely effectiveness of the innovation, are absent from current literature on traumainformed approaches in schools.

| Implications for practice and policy
From this review, it seems like the most prudent thing for school leaders, policymakers, and school mental health professionals to do would be proceed with caution in their embrace of a traumainformed approach as an overarching framework and conduct rigorous evaluation of this approach. We simply do not have the evidence (yet) to know if this works, and indeed, we do not know if using a trauma-informed approach could actually have unintended negative consequences for traumatized youth and school communities. We also do not have evidence of other potential costs in implementing this approach in schools, whether they be financial, academic, or other opportunity costs, and whether benefits outweigh the costs of implementing and maintaining this approach in schools.
That said, calling for caution in adopting TIC in schools does not preclude schools from continuing to implement evidence-informed programs that target trauma symptoms in youth, or that they should simply wait for the research to provide unequivocal answers. The benefit of the trauma-informed approach being made freely available by SAMHSA and other policymakers is that these components can form the basis for a school (or school district) to begin to adapt and apply this approach in schools.
An additional potential space for implementing a traumainformed approach could be within the various 3-tier models currently active in schools (often referred to as multi-tiered systems of supports [MTSS]) to give some form and structure to these efforts.
Indeed, recent scholarship has argued for the trauma-informed approach to be embedded within MTSS to take advantage of the primary prevention focus inherent in MTSS Tier 1 and Tier 2 efforts, along with the use of data via screening tools to identify students MAYNARD ET AL. | 13 of 18 who are impacted by trauma (Cavanaugh, 2016;Stephan, Suagi, Lever, & Connors, 2015;Zakzeski, Ventresco, & Jaffe, 2017). The process of screening students for trauma is not without its own controversy; however, as parent groups and school stakeholders sometimes oppose the idea of screening youth in schools for issues that they believe are the domain of parents and mental health systems to handle (Dowdy, Ritchey, & Kamphaus, 2010

| Roles and responsibilities
Please give brief description of content and methodological expertize within the review team. The recommended optimal review team composition includes at least one person on the review team who has content expertize, at least one person who has methodological expertize and at least one person who has statistical expertize. It is also recommended to have one person with information retrieval expertize.
Who is responsible for the below areas? Please list their names: • Content: All authors were responsible for the substantive content related to trauma-informed schools.
• Systematic review methods: Maynard has significant experience and expertize in systematic review methods. Farina, Dell, and Kelly have had training in and experience conducting systematic reviews.
• Statistical analysis: Maynard has been trained in meta-analytic techniques and has conducted several meta-analyses.

ACKNOWLEDGMENT
We appreciate the feedback from reviewers at the protocol and review stage and the work of the ECG Editorial Team in providing feedback and support in the publication of the protocol and review.

PLANS FOR UPDATING THE REVIEW
Maynard will be responsible for developing a plan for updating the review in approximately 3 years.

SOURCES OF SUPPORT
The review team received funding from the C2 ECG through a minigrant to support the conduct of this review.