Implementation Factors Influencing Peer-Delivered Behavioral Evidence-Based Interventions for Substance Use Disorders: A Scoping Review

Abstract

Peer recovery specialists (PRS) are increasingly recognized as key members of the substance use disorder (SUD) treatment workforce. Recent efforts have focused on expanding PRS roles to include the delivery of behavioral evidence-based interventions (EBIs), such as motivational interviewing, cognitive-behavioral therapy techniques, and brief interventions. This scoping review aims to identify the determinants that influence the implementation of PRS-delivered behavioral EBIs and the strategies used to optimize their delivery within diverse SUD treatment contexts. A systematic search was conducted in APA PsycINFO, Web of Science, Scopus, PubMed, and Google Scholar, following PRISMA-ScR guidelines. Studies were included if they examined PRS delivering behavioral EBIs for SUD and reported on at least one implementation outcome as defined by Proctor et al. (2011). Data extraction and thematic synthesis were conducted using a hybrid deductive-inductive coding framework. Twelve studies met inclusion criteria. The most commonly studied interventions included behavioral activation, motivational interviewing, and Screening, Brief Intervention, and Referral to Treatment (SBIRT). PRS-delivered behavioral EBIs demonstrated high acceptability, appropriateness, and feasibility, with strong participant engagement and satisfaction. Facilitators of implementation included the integration of PRS within existing service structures, the adaptability of interventions, and the unique relatability of PRS. Barriers included PRS role ambiguity, gaps in training, and systemic challenges such as lack of funding and limited access to adjunctive support services. Implementation outcomes such as adoption, sustainability, and cost were infrequently assessed, highlighting gaps in the current literature. The findings suggest that PRS-delivered behavioral EBIs hold promise in expanding access to evidence-based care for individuals with SUD. However, structured training, supervision, and organizational support are critical for successful implementation. Future research should prioritize evaluating long-term sustainability, supervision, and strategies to enhance the integration of PRS within healthcare systems. Incorporating methods to address systemic barriers faced by service recipients will be essential for maximizing the impact of PRS-delivered interventions in SUD treatment.

Substance use and substance use disorder (SUD) represent a significant and growing health burden worldwide. Over three million deaths annually are attributed to alcohol and drug use, making substance use one of the most critical public health challenges globally (World Health Organization, 2024). The impact of psychoactive drug use on the global disease burden surpasses any other risk factor for individuals aged 10–74 years (World Health Organization, 2024). Beyond the human toll, substance use imposes some of the highest costs on healthcare systems, with substantial economic consequences stemming from high rates of in-patient hospitalization, emergency department visits, and the consequences of physical health disorders exacerbated by substance use (Gryczynski et al., 2016). Despite these widespread impacts, access to treatment for SUD remains limited. It is estimated that only 9% of the 64 million individuals worldwide with drug use disorders receive treatment (United Nations Office on Drugs and Crime, 2024), and even fewer receive care that meets minimally adequate or evidence-based standards. Globally, just 7.1% of individuals with past-year SUD receive minimally adequate treatment, with stark disparities across income levels (Degenhardt et al., 2017). To address this gap, health systems around the world have increasingly prioritized strategies to expand access to clinically effective and cost-efficient care, while reducing the associated burden on healthcare resources (Magidson et al., 2021; Substance Abuse and Mental Health Services Administration & Office of the Surgeon General, 2016).

Peer recovery support services have emerged as a promising approach to help address the SUD treatment gap. Peer recovery specialists (PRS) – trained professionals who share lived or living experiences, notably SUD and recovery, with those they serve – are increasingly prominent team members employed to deliver vital services in the SUD treatment landscape (Center for Substance Abuse Treatment, 2009). Since their emergence in the 1990s, the peer workforce has grown steadily in both size and scope. Today, PRS provide support in a variety of settings, ranging from community organizations to clinical environments such as emergency departments and criminal justice programs (Eddie et al., 2019; Stack et al., 2022). Their roles have traditionally included emotional (e.g., sharing recovery stories, providing crisis support), informational (e.g., referrals and guidance to external resources), affiliational (e.g., connecting clients to community networks), and instrumental (e.g., assistance with housing and employment) components (Hagaman et al., 2023; Reif et al., 2014; Substance Abuse and Mental Health Services Administration, 2023; White, 2006). This range of services can complement the work of clinicians or serve as a standalone resource for individuals in recovery (Reif et al., 2014). As a non-traditional workforce, their benefits are numerous for reducing costs and enhancing treatment delivery (Magidson et al., 2021). Clients often report valuing the authenticity and empathy that PRS bring to their roles, which helps build trust and reduce resistance to interventions (Kleinman et al., 2021). The lived experience of PRS fosters a unique bond with clients, akin to the “wounded healer” model popularized in mutual aid groups (Francia et al., 2023; Scannell, 2021; White, 2006, 2009). However, the rapid expansion of the peer workforce has also highlighted challenges. Issues such as burnout, vicarious trauma, and high turnover rates are well-documented among PRS, often stemming from unclear role definitions and inadequate supervision (Bell et al., 2024). Without consistent professional recognition afforded to clinicians, PRS face threats of exploitation and are positioned as stopgaps for systemic failures in behavioral health care (Guy et al., In press). These challenges underscore the need for more formalized roles and responsibilities for PRS, which could enhance their professional status and clarify their position within treatment systems.

One avenue for addressing treatment gaps and expanding the role of PRS is through the delivery of evidence-based interventions (EBIs). Traditionally, EBIs have been administered by clinicians such as psychologists, counselors, and physicians. However, task-sharing models, or the redistribution of specific health-related tasks from highly specialized professionals to lay providers with appropriate training and supervision, have gained increasing attention as a strategy to enhance accessibility and efficiency in care delivery (World Health Organization et al., 2008). While non-specialist providers can successfully implement EBIs, maintaining fidelity requires robust training, structured supervision, and ongoing support (Bond et al., 2022; Sperber, 2020). Evidence from low- and middle-income countries (LMICs), however, has demonstrated the effectiveness of task-sharing behavioral EBIs with lay health workers, highlighting scalable training models that could inform task-sharing approaches in SUD treatment (Magidson et al., 2019).

In recent years, there has been growing interest in training PRS to deliver behavioral EBIs, providing a clearer and more structured scope for their roles. Behavioral EBIs are considered the foundation of SUD treatment and use psychological, social, and behavioral strategies to treat or manage substance use issues (Glasner & Drazdowski, 2019; Jhanjee, 2014; McGovern & Carroll, 2003). Examples of common behavioral EBIs for SUD include motivational interviewing, cognitive-behavioral therapy techniques including behavioral activation and problem-solving therapy, contingency management, and relapse prevention (Glasner & Drazdowski, 2019; Jhanjee, 2014). U.S. state certification programs increasingly mandate training in interventions such as motivational interviewing and cognitive-behavioral therapy to compliment the emotional, affiliational, informational, and instrumental components of peer support (SAMHSA, 2020). Recent clinical trials have demonstrated that peer-delivered EBIs yield positive and clinically significant outcomes, including reduced substance use, improved SUD treatment retention, enhanced mental health, and high levels of client satisfaction (Felton et al., 2023a; Jaguga et al., 2023a; Magidson et al., 2022). Beyond addressing workforce shortages, integrating PRS into EBI delivery has the potential to enhance reimbursement opportunities and reduce workforce challenges by supporting clear definitions of their roles within treatment systems.

To date, studies have largely focused on the effectiveness of services delivered by PRS, with limited work evaluating their implementation (Eddie et al., 2019; Reif et al., 2014; Stack et al., 2022). However, as the use of PRS in delivering these interventions grows, understanding the facilitators and barriers (i.e., determinants) of their successful implementation becomes increasingly critical. To address this, implementation science offers a valuable lens to examine the factors influencing the successful implementation of peer-delivered behavioral EBIs and their effects on key outcomes such as acceptability, feasibility, adoption, cost, and sustainability in real-world settings (Proctor et al., 2011, 2023). The overall objectives of this scoping review are to describe the nature and extent of the literature on (a) the determinants that shape the implementation of peer-delivered behavioral EBIs (i.e., motivational, cognitive-behavioral, and brief interventions) and (b) the strategies used to optimize their delivery within diverse substance use treatment contexts.

Methods

Study Design

We conducted a scoping review comprising empirical studies that describe peer-delivered behavioral EBIs for SUD. The review design was generated according to guidelines provided by Arksey and O’Malley (2005), Westphaln and colleagues (2021), and Mak and Thomas (2022). Results are reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR; See Supplemental Table 1 for a reporting checklist). The review was registered on October 31 st, 2024, in the Center for Open Science’s Open Science Framework repository, submitted during the full-text screening stage (https://osf.io/5ek7h).

Eligibility Criteria

We included studies that discussed PRS where the term “peer” encompassed individuals in SUD recovery, regardless of state or organizational certification, as well as people who currently use drugs that provide peer recovery support services (Center for Substance Abuse Treatment, 2009). Studies also were required to describe behavioral evidence-based interventions (EBIs) delivered by PRS, which were derived by using lists of behavioral EBIs for SUD described by McGovern and Carroll (2003), Glasner and Drazdowski (2019), and Jhanjee (2014). Behavioral EBIs included in the review were classified into three broad categories: motivational interventions, cognitive-behavioral interventions, and brief interventions. Motivational interventions, such as motivational interviewing (MI) and motivational enhancement therapy (MET), are collaborative, goal-oriented approaches designed to enhance an individual’s motivation to change by exploring and resolving ambivalence (Substance Abuse and Mental Health Services Administration, 2019). Cognitive-behavioral interventions, including Cognitive-Behavioral Therapy (CBT) and Seeking Safety, are grounded in principles of cognitive psychology and social learning theory. These approaches focus on developing new cognitive and coping skills to manage substance use behaviors, addressing maladaptive thought patterns, and improving emotional regulation (Nakao et al., 2021). Finally, brief interventions, such as Screening, Brief Intervention, and Referral to Treatment (SBIRT), are structured, time-limited approaches designed for use in non-specialized settings, including primary care, emergency departments, and community health clinics. These interventions typically involve screening, assessment, feedback, personalized advice, and follow-up sessions aimed at reducing substance use and facilitating referrals to specialized care when necessary (Mattoo et al., 2018).

Additionally, studies were required to discuss implementation characteristics of EBIs, verified by discussion of at least one of the following Proctor’s implementation outcomes: acceptability, adoption, appropriateness, cost, feasibility, fidelity, penetration, or sustainability (Proctor et al., 2011). The review was limited to studies published between January 1, 1999, and September 1, 2024, aligning with the emergence of formal peer certification (Chapman et al., 2018). We excluded research not published in English and studies that focused on peer sponsorship roles within mutual aid organizations (e.g., Narcotics/Alcoholics Anonymous), as these roles emphasize mutual, bidirectional support rather than the structured, one-directional service delivery model of PRS (White, 2006). Furthermore, we omitted studies related to peer support in areas unrelated to behavioral EBI delivery for SUD, such as services exclusively related to mental health, physical health support, harm reduction, or housing linkage. There were no exclusion criteria based on participant age, geographic location, or service setting. Studies involving youth, global populations, and diverse contexts were included. Only empirical articles reporting original results were included; reviews, protocols, and grey literature were excluded. The inclusion and exclusion criteria are summarized in Table 1.

Table 1.

Screening inclusionary and exclusionary criteria

Inclusion	Exclusion
Discusses peer recovery support services	Not published in English
PRS discussed are in formal employed or volunteer positions	PRS discussed are in “sponsorship” positions within mutual aid organization or people with lived experience working in a professional position (e.g., administrator, counselor, social worker, therapist)
Discusses behavioral evidence-based intervention (EBI) delivered by PRS (motivational, cognitive-behavioral, brief)	Protocol articles, reviews, and grey literature
Describes at least one implementation outcome of behavioral EBI (acceptability, adoption, appropriateness, cost, feasibility, fidelity, penetration, or sustainability) Published between 1/1/1999 to 9/1/2024

Review eligibility and exclusionary criteria.

Search Strategies

We developed search strategies that combined Medical Subject Heading (MeSH) and free-text terms related to PRS (e.g., “peer,” “people with lived experience”) and evidence-based interventions (e.g., “evidence-based treatment,” “evidence-based practice”). The search strings were generated with the University of Missouri’s Search Strategy Builder Tool (University of Missouri, 2025), and piloted by an author with database experience (AUTHOR INTIAL) to ensure accuracy. Our search targeted key databases, including APA PsycINFO^® (EBSCO), Web of Science^™ (Clarivate), Scopus (Elsevier), PubMed^®, and Google Scholar. The final review and extraction of citations were conducted on September 1 st, 2024. Results were exported to the bibliographic manager Zotero, and duplicates were removed using Rayyan (Ouzzani et al., 2016). A full list of search strings by database is included in Supplemental Table 2.

Study Selection

A total of 9,357 articles were identified through our initial literature searches. After removing duplicates and articles that immediately disqualified identified using automation tools (e.g., published before 1999, not published in English), 5,685 articles remained. Titles and abstracts of these remaining articles were screened by two reviewers (AUTHOR INTIAL). Primary reasons for exclusion at the title and abstract screening stage included no discussion of PRS roles (e.g., EBIs delivered by nurses or other clinical staff) and a lack of implementation outcomes (e.g., articles that focused solely on treatment effectiveness). Articles that met the inclusion criteria underwent a second, full-text screening stage by three reviewers (AUTHOR INTIAL). To reduce potential bias, reviewers [AUTHOR INTIAL] reviewed articles where [AUTHOR INTIAL] served as an author. Any disagreements regarding eligibility were resolved by the remaining authors. A total of 12 articles were selected for inclusion. The screening and selection process is illustrated in Fig. 1, which was generated using the PRISMA online application (Haddaway et al., 2022).

Fig. 1.

PRISMA Study Selection Flow Diagram

Data Extraction

Three authors (AUTHOR INTIAL) extracted data from the selected articles using the qualitative analysis software ATLAS.ti (ATLAS.ti Scientific Software Development GmbH, 2025). All members of this coding team had expertise on PRS services with prior publications examining PRS roles and implementation. The first and third authors previously led systematic reviews focused on non-traditional providers that involved qualitative coding and analyses, providing guidance on article screening and coding throughout the process (Anvari et al., 2023a; Bell et al., 2025). We applied a hybrid-deductive approach to code both a priori specified implementation outcomes and determinants to these outcomes, and generated new codes where necessary (Fereday & Muir-Cochrane, 2006). The extracted information included bibliographic details such as publication type and year, the country or location of the study, the authors’ research objectives, and sample size. Sample characteristics were also recorded, including PRS definition and role type, as well as characteristics of the target population and sample. We also captured information on study methodology and the context and setting in which the EBIs were delivered, such as rehabilitation centers, recovery community organizations, or other settings. The specific EBIs delivered by PRS were noted, and our primary implementation outcomes, as described by Proctor et al. (2011), were coded, along with the described determinants of these outcomes. To ensure reliability and consistency, coders piloted two articles to establish Cohen’s Kappa statistic above 0.6 before independently coding the remaining articles. Any discrepancies in the coding were discussed among the authors to ensure that the final codes were aligned with the study’s objectives.

Data Synthesis

To guide and structure the results, determinants of implementation outcomes were classified based on their facilitating or inhibiting relationships to the identified outcomes. Authors conducted a thematic analysis procedure by grouping segments from the coded data under the general categories of the implementation outcomes, allowing the establishment of subthemes (Mak & Thomas, 2022). Subthemes were developed for each implementation outcome based solely on the articles coded with that specific outcome (e.g., subthemes for acceptability were drawn only from articles coded as describing acceptability).Subthemes were created if discussed in at least 2 of the eligible articles. These subthemes were continuously reviewed for their validity and appropriateness, with irrelevant subthemes excluded. During the discussion phase, new subthemes were suggested and validated for inclusion in the final synthesis, ensuring that all relevant factors and relationships were captured. Table 2 includes an overview of the included studies.

Table 2.

Overview of included studies

Authors/Year	EBI(s)	Intervention target population(s)	Publication type	Study Design	Sample Size(s)	Context/Setting	Outcomes Discussed
Anvari et al., 2022 a	BA	People living with HIV and/or SUD	Quantitative	Fidelity monitoring of two intervention trial	PRSs: 2 Patients: 25	HIV treatment center, Khayelisha, South Africa Community resource center, Baltimore, MD, USA	Fidelity
Anvari et al., 2023a,bb	BA	Patients receiving methadone treatment who either newly initiated treatment or exhibited adherence challenges	Descriptive (case series)	Type 1 hybrid effectiveness-implementation open-label pilot	PRSs: 1 Patients: 3	Community-based opioid treatment center, Baltimore, MD, USA	Acceptability, Fidelity
Bogan et al., 2020	SBIRT, MI	Emergency department patients with SUD	Descriptive (pilot implementation program development)	Pilot implementation program following Chamberlain’s Stages of Implementation	PRSs: Not specified (“over 200 ED nurses and providers” Patients: 6523	Three emergency departments, South Carolina, USA	Acceptability, Adoption, Appropriateness, Feasibility, Fidelity, Penetration, Sustainability
Crisanti et al., 2016	Seeking Safety (SS) – CBT for trauma & SUD	People with SUD and trauma and/or PTSD	Quantitative	Post-training evaluation of a brief SS training	PRSs: 16 Behavioral health providers: 21	USA, otherwise unspecified	Fidelity
Felton et al., 2023a, d	BA	People with moderate or severe SUD	Mixed-methods	Open-label “proof-of-concept” feasibility and preliminary effectiveness trial	PRSs: 1 Patients: 8	Community resource center, Baltimore, MD, USA	Acceptability, Appropriateness, Feasibility, Fidelity
Hansen et al., 2022	SBIRT, MI	People with SUD	Quantitative	PRS training and observational patient outcome monitoring	PRSs: 155 Patients: 180	Three recovery community organizations, Houston, Texas, USA	Acceptability, Adoption, Appropriateness
Jaguga et al., 2023c	Screening and brief intervention (SBI), MI	Kenyan youth aged 15–24	Mixed-methods	Open-label pilot	PRSs: 2 Patients: 100	Youth clinic, western Kenya	Acceptability, Adoption, Appropriateness, Feasibility, Fidelity, Sustainability
Jaguga et al., 2023c	SBI, MI	Kenyan youth aged 15–24	Descriptive (pilot implementation program development)	Intervention adaptation following ADAPT-ITT framework	Clinic staff: unspecified PRSs: 3 Youth stakeholders: 12 Expert stakeholders: 3	Youth clinic, western Kenya	Acceptability, Appropriateness, Feasibility
Kleinman et al., 2023 b	BA	Patients receiving methadone treatment who either newly initiated treatment or exhibited adherence challenges	Qualitative	Intervention adaptation feedback solicitation following ADAPT-ITT framework	Program staff, providers, and local PRSs: 12 Patients: 20	Community-based opioid treatment center, Baltimore, MD, USA	Acceptability, Appropriateness, Feasibility
Magidson et al., 2021a, ba	BA	People living with HIV and SUD	Quantitative	Type 1 hybrid effectiveness-implementation trial	PRSs: 1 Patients: 61	HIV treatment center, Khayelisha, South Africa	Acceptability, Appropriateness, Feasibility, Fidelity
Magidson et al., 2022 b	BA	Patients receiving methadone treatment who either newly initiated treatment or exhibited adherence challenges	Quantitative	Type 1 hybrid effectiveness-implementation open-label pilot	PRSs: 1 Patients: 37	Community-based opioid treatment center, Baltimore, MD, USA	Acceptability, Appropriateness, Feasibility, Fidelity, Sustainability
Satinsky et al., 2020 d	BA	People with moderate or severe SUD	Qualitative	Intervention adaptation feedback solicitation following ADAPT-ITT framework	Community PRSs: 6 Center staff: 5 Center clients: 30	Community resource center, Baltimore, MD, USA	Acceptability, Appropriateness, Feasibility

^aFidelity findings in Anvari et al. (2022) are from the Felton et al., 2023a, b; Magidson et al. (2021a, b) trials.

^bAnvari et al. (2023a, b; case series), Kleinman et al. (2023; intervention adaptation) and Magidson et al. (2022; implementation-effectiveness outcomes) are the same intervention trial.

^cJaguga et al. (2023; implementation outcomes) and Jaguga, Ott Jaguga et al. (2023a, b; intervention adaptation) are the same intervention trial.

^dFelton et al. (2023a, b; preliminary implementation and effectiveness outcomes) and Satinsky et al. (2020; intervention adaptation) are the same intervention trial.

Results

Study Descriptions

The included studies (N = 12) varied in their methodological approaches, with quantitative studies comprising 41.7% (5/12), mixed-methods or descriptive designs accounting for 41.7% (5/12), and qualitative studies making up the remaining 16.6% (2/12). Sample sizes for PRS ranged from 1 to 155, while non-PRS participants (e.g., patients/service recipients, healthcare providers, or stakeholders) ranged from 3 to 6,523. The studies were conducted in diverse settings, including community-based opioid treatment centers, HIV treatment centers, recovery community organizations, emergency departments, youth clinics, and general community resource centers, in both US and non-US (i.e., Kenya, South Africa) contexts.

Cognitive-behavioral interventions were included in 58.3% (7/12) of studies, making it the most frequently studied category of peer-delivered EBIs. The most commonly examined cognitive-behavioral intervention was Behavioral Activation (BA), a structured therapy that encourages engagement in meaningful activities to improve mood by addressing avoidance behaviors (Kanter et al., 2010). BA has been adapted for peer delivery to support individuals in reducing substance use by increasing engagement in substance-free rewarding behaviors (Anvari, Kleinman et al., 2023). Additionally, Seeking Safety (SS), a cognitive-behavioral therapy designed for individuals with co-occurring trauma and substance use disorders, was evaluated in 8% (1/12) of studies (Najavits, 2002). Motivational interventions were examined in 33% (4/12) of studies, with Motivational Interviewing (MI) as the primary approach. MI is a collaborative, goal-oriented intervention that enhances motivation for behavior change by exploring and resolving ambivalence through structured counseling (Hettema et al., 2005; Substance Abuse and Mental Health Services Administration, 2019). Brief interventions appeared in 25% (3/12) of studies, with Screening, Brief Intervention, and Referral to Treatment (SBIRT) as the primary intervention. SBIRT is a structured, time-limited approach commonly implemented in non-specialized settings such as primary care, emergency departments, and community health clinics (Mattoo et al., 2018). It focuses on identifying individuals at risk, providing targeted interventions, and facilitating referrals to appropriate treatment services (Agerwala & McCance-Katz, 2012).

The following results describe the implementation outcomes (Acceptability, Appropriateness, Feasibility, Fidelity, Adoption, Penetration, Sustainability) of these peer-delivered interventions and their facilitating or inhibiting determinants. As cost was not described in the eligible articles, it is not included as a theme in our results.

Acceptability

Acceptability, or the extent to which stakeholders perceive an intervention as agreeable, palatable, or satisfactory, was discussed in ten articles (Anvari, Kleinman et al., 2023; Bogan et al., 2020; Felton et al., 2023; Hansen et al., 2022; Jaguga et al., 2023; Jaguga, Ott, Jaguga et al., 2023a, b; Kleinman et al., 2023; Magidson et al., 2021a, b, 2022; Satinsky et al., 2020). Quantitative findings demonstrated high acceptability of PRS-delivered behavioral EBIs, with strong participant engagement (e.g., 86.5–100% intervention initiation, evidence of repeated attendance), and moderate to high participant brief ratings of acceptability and satisfaction (Hansen et al., 2022; Jaguga et al., 2023a; Magidson et al., 2021a, b, 2022). Measures of acceptability included Likert scale ratings of training satisfaction (Hansen et al., 2022), a priori-defined participation thresholds (e.g., session attendance), and a validated implementation outcome instrument (i.e., published by the Applied Mental Health Research Group; Magidson et al., 2021a, b, 2022). PRS themselves also reported high satisfaction with EBI delivery and intervention training (Hansen et al., 2022; Jaguga et al., 2023a). Beyond these quantitative findings, the qualitative analysis identified two facilitators of acceptability: Preference for Peer Delivery and Tailored Intervention Delivery, and one barrier: Preparedness and Skill of PRS.

Preference for Peer Delivery

A preference among participants and stakeholders for interventions led by individuals with lived experience was discussed as a facilitator to acceptability in five articles (Anvari, Kleinman et al., 2023; Felton et al., 2023; Jaguga et al., 2023; Kleinman et al., 2023; Satinsky et al., 2020). Participants frequently emphasized the value of working with PRS, highlighting the comfort and trust fostered by shared lived experiences (Anvari, Kleinman et al., 2023; Kleinman et al., 2023; Satinsky et al., 2020). Many clients reported that PRS’ personal recovery journeys made them more approachable, relatable, and effective at engagement during intervention delivery, serving as role models who inspired motivation for recovery (Felton et al., 2023b; Kleinman et al., 2023; Satinsky et al., 2020). In a trial of a brief MI intervention for youth, participants expressed greater trust and openness with PRS due to their shared background and age (Jaguga et al., 2023). Additionally, when working in collaboration with other providers, PRS were viewed as integral to the success of participant engagement, with one staff participant sharing they believed patient attendance would be nonexistent without the presence of PRS (Kleinman et al., 2023).

Tailored Intervention Delivery

Tailored intervention delivery, or the importance of adaptability to align interventions with participant needs and qualities of PRS, was discussed as a facilitator to acceptability in three articles (Anvari, Kleinman et al., 2023; Jaguga et al., 2023; Kleinman et al., 2023). Timing was identified as a critical factor, with PRS and participants noting that introducing a PRS intervention too early or too forcefully could feel overwhelming, whereas strategic timing (e.g., during medications for opioid use disorder [MOUD] dose stabilization) could enhance intervention effectiveness (Kleinman et al., 2023). Participants also stressed the need for flexibility in the structure of interventions delivered by PRS, such as adjusting session duration based on individual needs and meeting in alternative locations like outdoor spaces or community sites - reflecting the often informal and emotional quality of peer relationships (vs. what is typical in clinical relationships) (Kleinman et al., 2023). Finally, PRS’ lived experience offered valuable feedback for modifying intervention content to enhance accessibility, such as simplifying language, using colloquial terms for substances, and removing potentially stigmatizing language to improve participant engagement (Jaguga et al., 2023).

Preparedness and Skills of PRS

Preparedness and skill of PRS, or the extent to which PRS are adequately trained and knowledgeable to deliver interventions effectively, was discussed as a barrier to acceptability in two articles (Jaguga et al., 2023a; Kleinman et al., 2023). While PRS were generally valued for their lived experience and approachability, some participants expressed concerns about their intervention preparedness and population-specific knowledge. Youth participants in one study reported feeling uncomfortable with certain PRS, citing reasons such as lack of familiarity, perceived judgmental attitudes, or stern demeanor. Other youths in the study felt that PRS were ill-prepared to deliver the intervention, indicating that gaps in expertise and training could hinder effectiveness (Jaguga et al., 2023). Similarly, concerns were raised about the clinical scope of PRS roles, with some staff in a study of peer-delivered BA describing concerns regarding whether PRS had the necessary skills to work with individuals experiencing severe mental health conditions (Kleinman et al., 2023), with one staff member emphasizing that these cases require formal clinical expertise beyond PRS training (Kleinman et al., 2023).

Appropriateness

Appropriateness, defined as the perceived fit, relevance, or compatibility of an intervention within a given setting or for a particular population, was discussed in ten articles (Anvari, Kleinman et al., 2023; Bogan et al., 2020; Felton et al., 2023; Hansen et al., 2022; Jaguga et al., 2023; Jaguga, Ott, Jaguga et al., 2023a, b; Kleinman et al., 2023; Magidson et al., 2021a, b, 2022; Satinsky et al., 2020). In the two studies that assessed appropriateness quantitatively, the construct referred specifically to the appropriateness of PRS-delivered behavioral EBIs within clinical settings. In Magidson et al. (2021a, b), patients receiving services in an HIV care setting in South Africa rated appropriateness using a validated four-point scale developed by Haroz et al. (2019), with 0 = “not at all” and 3 = “a lot.” In Jaguga et al. (2023), peer providers and clinic leaders in a youth clinic in Kenya rated appropriateness using the same measure. When collected, appropriateness was highly rated using this brief measure (Jaguga et al., 2023a; Magidson et al., 2021a, b). Beyond these quantitative findings, the qualitative analysis identified three facilitators of appropiateness: Integration with Existing System, Adaptation Based on Stakeholder Feedback, and Role Specific Fit for PRS, as well as one barrier: Lack of Adjunctive Support for Patients.

Integration with Existing System

Integration with existing systems, or the extent to which peer-delivered EBIs align with and complement the structure and goals of the implementing setting, was identified as a key facilitator of appropriateness in two articles (Bogan et al., 2020; Jaguga et al., 2023a). Findings highlight that embedding PRS-delivered interventions within existing workflows and aligning them with institutional priorities enhances their appropriateness and likelihood of adoption. In emergency department (ED) settings, PRS patient navigators were embedded within clinical workflows, working directly with staff and patients to deliver SBIRT services (Bogan et al., 2020). Their integration allowed them to access electronic health records, observe screening responses, and coordinate with ED staff to prioritize patient interventions, ensuring seamless alignment with existing procedures (Bogan et al., 2020). Similarly, in a primary care setting, clinic leaders and PRS at a youth clinic reported that the screening and brief intervention program fit well within existing clinic processes and did not conflict with other services (Jaguga et al., 2023). Clinic leaders further emphasized that the intervention was compatible with the clinic’s overall mission and goals, specifically in addressing the unmet need for substance use services among youth (Jaguga et al., 2023).

Adaptation Based on Stakeholder Feedback

Adaptation based on stakeholder feedback, or the process of continuously refining interventions based on input from key stakeholders, was identified as a facilitator of appropriateness in three articles (Bogan et al., 2020; Jaguga et al., 2023b; Magidson et al., 2022). PRS and other stakeholders played an active role in modifying intervention content to ensure its relevance and fit within the delivery context. For example, during training sessions for a brief youth MI intervention, PRS and facilitators regularly reviewed intervention materials, identified issues with understandability, and built consensus on necessary adjustments to enhance clarity and accessibility (Jaguga et al., 2023). Similarly, in the development of a PRS-delivered BA intervention, feedback was gathered from multiple stakeholder groups, including PRS, treatment program staff, and patients to refine the intervention by integrating problem-solving strategies to improve medication adherence (Magidson et al., 2022). Furthermore, PRS directly involved in intervention delivery provided input on adapting manuals and handouts to improve usability and effectiveness (Magidson et al., 2022). In an ED setting, ongoing feedback was systematically collected from participating EDs and outpatient treatment programs on a monthly basis, allowing for iterative adjustments to improve service delivery and effectiveness (Bogan et al., 2020).

Role-Specific Fit for PRS

Role-specific fit, or the alignment of an intervention with the skills, strengths, and expectations of PRS, was identified as a facilitator of appropriateness in five articles (Anvari, Kleinman et al., 2023; Felton et al., 2023; Jaguga et al., 2023; Kleinman et al., 2023; Satinsky et al., 2020). Findings highlight that PRS-delivered behavioral EBIs are more appropriate when they build on peer strengths, maintain clear boundaries, and align with their intended role. Participants emphasized that PRS were particularly effective when interventions leveraged their lived experience, relatability, and ability to build trust with clients, rather than requiring them to take on roles beyond their scope, such as conducting formal clinical assessments or diagnosing mental health conditions (Felton et al., 2023b; Satinsky et al., 2020). Concerns were raised that expecting PRS to manage complex psychiatric symptoms or provide clinical interventions without appropriate training could exceed their intended role and undermine their effectiveness in providing peer-based support. The relatability of PRS was discussed as especially critical in formal treatment settings, where PRS were able to reach clients in ways that traditional counselors could not. The PRS role could help extend interventions beyond the boundaries of a formal clinical role, for example, by accompanying participants to do meaningful activities in the community during a BA intervention (Kleinman et al., 2023). Additionally, in another study of PRS-delivered BA, the structured nature of the intervention was perceived as appropriate for PRS, as it provided a clear framework that aligned with their role while still allowing flexibility in delivery (Anvari, Kleinman et al., 2023).

Lack of Adjunctive Support for Patients

A lack of adjunctive support, or the absence of additional resources and services needed to complement PRS-delivered interventions, was identified as a barrier to appropriateness in two articles (Kleinman et al., 2023; Satinsky et al., 2020). Structural and psychosocial instability, including homelessness, financial insecurity, and lack of access to essential services, were repeatedly cited as barriers to client engagement (Kleinman et al., 2023; Satinsky et al., 2020). Both staff and clients emphasized that addressing basic needs such as housing, food, and clothing was necessary before individuals could meaningfully participate in behavioral interventions, as many clients were overwhelmed by daily survival concerns (Satinsky et al., 2020). Additionally, participants noted that for individuals with severe substance use, particularly opioid use disorder, a BA intervention alone would be insufficient unless paired with MOUD and other treatment supports (Satinsky et al., 2020). Given these challenges, PRS suggested integrating case management and linkage to care services alongside PRS-delivered interventions to improve appropriateness and effectiveness (Satinsky et al., 2020).

Feasibility

Feasibility, or the extent to which the intervention was practically implemented as intended (i.e., actual fit, utility) was discussed in eight articles (Bogan et al., 2020; Felton et al., 2023b; Jaguga et al., 2023a; Jaguga, Ott, Jaguga et al., 2023a, b; Kleinman et al., 2023; Magidson et al., 2021a, b, 2022; Satinsky et al., 2020). Articles varied in their approaches to this implementation outcome, with three focusing on feasibility from the perspective of intervention providers (Bogan et al., 2020; Jaguga et al., 2023a; Jaguga, Ott, Jaguga et al., 2023a, b) and five from the perspective of intervention recipients (Felton et al., 2023b; Kleinman et al., 2023; Magidson et al., 2021a, b, 2022; Satinsky et al., 2020). In the four articles that reported quantitative evidence of feasibility, one reported as uptake rates (Felton et al., 2023) and two as both uptake rates and brief scale ratings from intervention recipients (Magidson et al., 2021a, b, 2022), all of which were high; the third article, reporting feasibility scale ratings from leadership, suggested lower perceived feasibility (Jaguga et al., 2023). Qualitative findings reported in articles indicated one facilitator of feasibility, namely Client-centered Service Delivery, as well as one barrier, Competing Client Priorities. The theme of Agency-level Factors was discussed as both a facilitator and a barrier. Notably, feasibility determinants varied by perspective: recipient-focused studies emphasized service delivery factors, while provider-focused studies highlighted organizational-level influences.

Client-centered Service Delivery

Client-centered service delivery – the extent to which EBI delivery was implemented accounting for clients’ unique needs and circumstances, with the aim of enhancing feasibility – was discussed as a facilitator to feasibility in three articles (Felton et al., 2023b; Kleinman et al., 2023; Satinsky et al., 2020). Specifically, feasibility was facilitated by integrating novel EBIs into existing services to minimize participant feelings of being overwhelmed or frustrated by the expectation of more appointments and obligations (Felton et al., 2023b; Satinsky et al., 2020). Articles also discussed that participation was more feasible if engagement with PRS created opportunities for benefits above and beyond the EBI itself, including incentives for participation (Kleinman et al., 2023) and linkages to housing or MOUD (Satinsky et al., 2020). Lastly, all three articles emphasized the importance of flexibility as enhancing feasibility, including conducting sessions at different times and locations or varying session lengths as needed. These types of accommodations allowed clients to participate in services even with unpredictable or busy schedules.

Lack of Adjunctive Support for Patients

Lack of adjunctive support was again discussed in context of feasibility, featured as a barrier in three articles (Felton et al., 2023b; Kleinman et al., 2023; Satinsky et al., 2020). Although client-centered service delivery obviated many barriers to participation, many challenges remained salient. For example, clients participating in PRS-delivered EBI services lacked access to basic needs (e.g., food, housing) that took higher priority than keeping intervention appointments (Satinsky et al., 2020). PRS and other program staff also discussed barriers for clients who were still actively engaged in heavy substance use, in which case cycles of withdrawal and intoxication or activities to obtain drugs could make focus on continued engagement with services less feasible (Satinsky et al., 2020). Beyond complications presented by substance use, time commitments of participating in the study may seem not feasible for clients who have other obligations to treatment services (e.g., intensive outpatient programming) or employment (Felton et al., 2023b; Kleinman et al., 2023).

Agency-level Factors

Agency-level factors – features of the larger organizational context which facilitated or hindered feasibility – were discussed as a facilitator or barrier in three articles (Bogan et al., 2020; Jaguga, Kwobah, Jaguga et al., 2023a, b; Jaguga, Ott, Jaguga et al., 2023a, b). Some facilitating factors related to agency resources, such as adequate staffing and space (Jaguga, Kwobah, Jaguga et al., 2023a, b); others related to communication, including initial planning meetings and close working relationships between PRS and other agency staff (Bogan et al., 2020). Thoughtful selection of an EBI given agencies’ existing services and workflow was also described as a facilitator, in that EBIs which could be easily learned by PRS and integrated into existing agency processes were more feasible (Bogan et al., 2020; Jaguga, Kwobah, Jaguga et al., 2023a, b; Jaguga, Ott, Jaguga et al., 2023a, b). However, one article also discussed agency-level factors as a barrier to feasibility, specifically related to lack of funding for ongoing PRS training and client transportation, as well as potential of leadership perceiving the EBI as lower-priority compared to other client needs (Jaguga, Kwobah, Jaguga et al., 2023a, b).

Fidelity

Fidelity, or the degree to which the intervention was delivered as planned (including adherence to protocols), was discussed in seven articles (Anvari et al., 2022; Anvari, Kleinman et al., 2023; Bogan et al., 2020; Felton et al., 2023; Jaguga et al., 2023; Magidson et al., 2021a, b, 2022). Generally, articles did not discuss barriers and facilitators to fidelity (e.g., using qualitative interviews), but there was a degree of variability in terms of how the outcome of fidelity was measured. As such, findings are presented below as approaches to fidelity measurement, namely: Fidelity through Supervision, Fidelity Measured by External Raters, and PRS-rated Fidelity.

Fidelity Through Supervision

Five articles (Anvari et al., 2022; Anvari, Kleinman et al., 2023; Bogan et al., 2020; Felton et al., 2023; Magidson et al., 2022) discussed regular supervision as a method for ensuring ongoing fidelity, typically including review and discussion of difficult cases. When specified, supervision occurred on a weekly basis and was conducted by a clinical psychologist (Anvari et al., 2022; Anvari, Kleinman et al., 2023; Magidson et al., 2022) or an experienced clinician (Bogan et al., 2020), often the same staff who conducted PRS’ initial EBI training.

Fidelity Measured by External Raters

Six of the seven articles described fidelity as coded by an independent rater viewing or listening to recorded sessions, typically using a checklist of intervention components (Anvari et al., 2022; Anvari, Kleinman et al., 2023; Felton et al., 2023; Jaguga et al., 2023; Magidson et al., 2021a, b, 2022). One article stated that ratings were provided for all sessions (Jaguga et al., 2023), though more commonly articles reported rating of a subset of recorded sessions, usually 20% (Anvari, Kleinman et al., 2023; Magidson et al., 2021a, b, 2022). Three trials (Anvari et al., 2022; Felton et al., 2023b; Magidson et al., 2021a, b), incorporated items from the Enhancing Assessment of Common Therapeutic Factors (ENACT; Kohrt et al., 2015) scale to evaluate PRS-specific competencies, such as effective use of self-disclosure and avoidance of stigmatizing language.

Peer-rated Fidelity

Three articles described processes for PRS to self-rate fidelity following each intervention session using a checklist approach (Anvari et al., 2022; Magidson et al., 2021a, b, 2022), in addition to fidelity assessments conducted by external raters. In all three articles, PRS rated fidelity more highly on average than external raters, suggesting the importance of gathering information about fidelity using multiple sources.

Adoption and Penetration

Adoption (the degree to which the intervention was taken up or implemented by the target audience; i.e., uptake, utilization) and Penetration (the integration of the intervention within the service setting or system; i.e., reach, spread) were discussed in only two articles (Bogan et al., 2020; Jaguga et al., 2023a). Adoption and penetration were the least frequently examined implementation outcomes, suggesting a broader lack of consideration for the long-term maintenance, scale-up, and integration of PRS-delivered EBIs beyond initial funding and research trials. Adoption was quantitatively assessed in one study (Jaguga et al., 2023), in which both PRS and organizational leadership rated the uptake of the intervention; while both groups gave high ratings, leadership rated adoption more highly than PRS. Penetration was described qualitatively in Bogan et al. (2020), where integration and ongoing maintenance of intervention processes (e.g., adding screening to triage; establishing partnerships between clinical staff and PRS to facilitate referrals) reflected deeper incorporation of the intervention within the service setting. The article highlighted close communication, engagement across multiple departments, and explicit commitment from senior leadership as facilitators of both adoption and penetration.

Sustainability

Sustainability, or the extent to which an intervention is maintained or institutionalized within a setting after initial implementation, was discussed in three articles (Bogan et al., 2020; Jaguga et al., 2023b; Magidson et al., 2022). While it was one of the least frequently examined implementation outcomes in the included studies, this likely reflects the early stage of research on PRS-delivered EBIs rather than a lack of focus on sustainability. Many of the identified studies were pilot or feasibility trials, forming the foundation for larger ongoing or planned trials aimed at evaluating longer-term integration and scalability. However, three facilitators of sustainability were identified: Champion Support, Integration with Existing System, and Supervision to Support Peer Self-Care.

Champion Support

Gaining support from leadership and clinical staff was identified as facilitator of sustainability in two articles (Bogan et al., 2020; Jaguga et al., 2023a). Findings highlight that securing leadership support and using data-driven advocacy are useful strategies for sustaining PRS-delivered EBIs. During a brief youth MI intervention, clinic leaders identified internal champions—including nurses, psychologists, and nutritionists—who could advocate for program continuation, secure funding, and establish external partnerships to strengthen sustainability (Jaguga et al., 2023). In an ED setting, providing frequent feedback to ED staff regarding the program’s positive outcomes was instrumental in dissolving stigma and reinforcing the importance of addiction treatment (Bogan et al., 2023). Feedback included data on patient initiation rates, treatment retention, and reduced ED visits, as well as de-identified thank-you letters from patients and families (Bogan et al., 2023). These efforts not only increased staff buy-in but also strengthened institutional commitment, ensuring that the PRS-delivered intervention was recognized as valuable.

Integration with Existing System

As was discussed in the context of appropriateness, embedding PRS and their interventions within the existing infrastructure of the implementation setting was identified as a facilitator of sustainability in two articles (Jaguga et al., 2023a, b; Bogan et al., 2023). During a brief youth MI intervention, the intervention was fully integrated into routine clinical procedures, allowing participants to be assigned to available PRS as part of standard care rather than a separate, temporary initiative (Jaguga et al., 2023a, b). Clinic leaders further reported that PRS were fully stationed at the clinic and would continue delivering the intervention beyond the study period, ensuring ongoing implementation and reducing their reliance on short-term research funding (Jaguga et al., 2023a, b). Similarly, in ED settings, screening tools utilized in the intervention were embedded into triage assessments and integrated into electronic health records (Bogan et al., 2023).

Supervision To Support Peer Self-Care

Supervision that emphasized self-care and wellness was identified as a facilitator of sustainability in two articles (Bogan et al., 2020; Magidson et al., 2022). In one study, weekly supervision sessions began with a self-care check-in, allowing PRS to discuss personal barriers to wellness, maintaining recovery supports, and ensuring appropriate role boundaries (Magidson et al., 2022). Similarly, in an ED setting, supervisors not only monitored intervention fidelity but also helped reinforce recovery specific self-care for PRS (Bogan et al., 2020).

Discussion

Across twelve studies, evidence highlighted that the delivery of behavioral EBIs for SUD by PRS was found to be highly acceptable, appropriate, and feasible, with strong participation and high satisfaction reported by both service recipients and PRS. Facilitators of the implementation tended to those aspects of EBIs which were modifiable, including allowing flexibility in structure and incorporating PRS and other stakeholder input into adaptation. Barriers, however, reflected systematic challenges, including a lack of institutional support for PRS interventions (i.e., funding, support from other staff), and the inability of PRS to meet the resource-related needs of service recipients. Implementation outcomes that were infrequently described included considerations of sustainability, cost, broader adoption, penetration,, and specific supervision strategies to support PRS in maintaining fidelity and role adherence. Given the need to expand the workforce capable of delivering EBIs, and the need to clarify and solidify PRS roles, results are promising but reveal important areas of direction for the ongoing implementation and scaling of PRS delivery.

The role of PRS in delivering behavioral EBIs aligns with broader task-sharing that leverage non-traditional providers in behavioral health settings. Similar to PRS, non-traditional providers including community health workers (CHWs), nurses, case managers, and social workers, have been effectively trained to deliver mental health and substance use interventions, demonstrating comparable outcomes to professionally delivered treatments (Pérez & Martinez, 2008; Singla et al., 2017). These findings parallel those of a systematic review on the implementation of task-shared cognitive-behavioral therapy in LMICs which identified similar facilitators and barriers to implementation (Verhey et al., 2020). Specifically, structural barriers tied to low socioeconomic status—such as poverty, unemployment, unstable housing, and low literacy—were found to hinder client participation. Additionally, the review emphasized that high-quality training, supervision, and integration within implementing entities were critical for increasing provider confidence and competence, reinforcing the importance of these factors in PRS-led interventions. These parallels suggest that lessons from global task-sharing initiatives may inform strategies for optimizing PRS-delivered EBIs, particularly in addressing structural barriers and strengthening workforce development.

A key theme in the literature on task-sharing models is the importance of comprehensive training, supervision, and ongoing support for non-traditional providers. Findings from this review highlight that PRS training quality and preparedness were critical to acceptability, as gaps in training led to concerns about PRS competency (Jaguga et al., 2023a; Kleinman et al., 2023). These concerns mirror challenges observed in other non-traditional provider models. In their recommendations for the training of non-traditional providers, Codd and Ludgate (2017) emphasize that training must go beyond didactic instruction and incorporate role-play practice, case supervision, and booster training to reinforce skills. The need for hands-on skill-building is reinforced by studies like Ramos et al. (2018), who found that roleplaying and simulation exercises were essential to CHWs’ ability to implement SBIRT effectively. Similarly, Wennerstrom et al. (2015) found that CHWs delivering behavioral interventions valued interactive training methods and regular skill reinforcement, suggesting that training and supervision should integrate opportunities for practice, feedback, and ongoing mentorship. However, while these approaches strengthen PRS competency and intervention fidelity, they are also resource-intensive, requiring agencies to allocate time and licensed staff for training and supervision (Bond et al., 2022; Sperber, 2020). This presents a paradox: PRS are increasingly utilized to fill workforce shortages, yet their successful integration depends on infrastructure that is often stretched thin. To maximize the scalability of PRS-led EBIs, future research should explore efficient training and supervision models that balance rigor with feasibility, such as blended learning approaches, peer-led supervision models, or scalable competency-based training frameworks.

Another key finding in this review was that PRS-delivered interventions were more successful when integrated into existing service workflows (Bogan et al., 2020; Jaguga et al., 2023a). This aligns with research on other task-sharing of mental health interventions, which suggests that embedding non-traditional providers within established care systems improves intervention feasibility and sustainability (Fortuna et al., 2018). For example, a review of 37 studies on task-sharing mental health interventions found efforts to integrate within the implementing organization increased provider confidence and competence (Le et al., 2022). Failing to fully consider integration, especially in pre-implementation stages, can lead to PRS-delivered EBIs failing due to a lack of staff buy-in. One major barrier is that staff and leadership in implementing organizations may not fully understand non-traditional provider roles, leading to skepticism about their scope of practice or reluctance to incorporate them into care teams (Bell et al., 2025; Payne et al., 2017). This can be exacerbated when organizational leadership does not provide clear guidance on how non-traditional providers should be integrated or how their contributions align with broader institutional goals. These barriers mirror the challenges noted in the present review, where PRS-delivered interventions faced obstacles when PRS were not fully integrated into the care team or lacked institutional support (Kleinman et al., 2023; Satinsky et al., 2020). By contrast, examples of successful integration strategies are described by Wennerstrom et al. (2015), which included creating clear job descriptions for their CHWs, holding regular team meetings, and providing structured mentorship and feedback. These strategies parallel recommendations for PRS workforce development, where structured support and role definition are key to enhancing sustainability (Bell et al., 2024; Guy et al., 2025).

However, a broader challenge in task-sharing models is the expectation that non-traditional providers are expected to fill systemic gaps without being given adequate resources or institutional support. This issue has been aptly described by Guy et al. (2025) as the “fallacy of the idealized system,” – or the expectation that issues with housing, employment, and physical health will be neatly solved by growing a workforce that is woefully underequipped to address these issues. Findings from this review mirror these concerns, as PRS often lacked resources to adequately support clients dealing with homelessness, financial insecurity, and other unmet social needs (Kleinman et al., 2023; Satinsky et al., 2020). While supervision and self-care strategies can help mitigate stress, long-term sustainability requires investment in systemic solutions that support both PRS and the populations they serve. Problems at the magnitude of homelessness are unlikely to be solved in the short term, but PRS can be immediately supported by including adjunctive components in interventions that would allow them to refer individuals to higher levels of support. For example, a PRS delivering MI who notices that an individual at a methadone clinic experiencing homelessness should be able to connect that individual with housing support. Not only would this change likely increase the effectiveness of behavioral EBIs, but it would also reduce frustration from PRS that feel their purpose can never be fully realized without addressing resource issues or that they are alone in supporting individuals in the context of systemic failures (Guy et al., 2024).

The expansion of PRS into the delivery of behavioral evidence-based EBIs raises other important ethical considerations, particularly when peer roles begin to overlap with clinical responsibilities. While many states incorporate elements of interventions like MI and SBIRT into peer training (e.g., Florida, Illinois, Indiana, Maine, Massachusetts, and Ohio), concerns remain about the potential for ‘role drift’ into clinical functions (Bell et al., 2024; SAMHSA, 2020). The National Association of Peer Supporters (N.A.P.S.; recently dissolved) has explicitly warned against the co-optation of peer roles within traditional treatment settings, emphasizing that peers should not be expected to endorse or enforce specific clinical treatments (N.A.P.S., 2019). The risk is that, over time, PRS may adopt the language, responsibilities, and worldview of clinical staff, gradually shifting away from the foundational principles of peer support, such as mutuality and shared lived experience. The integration of EBIs into peer-delivered services presents a broader philosophical debate regarding the role of peer support in behavioral health. If peers are positioned as cost-effective substitutes for clinicians rather than as unique providers of recovery support, there is a danger that the core ethos of peer work (centered on lived experience, mutual empowerment, and non-hierarchical relationships) could be diminished (SAMHSA, 2023; White, 2005). Future research should further explore how to balance the integration of EBIs into peer work while safeguarding the integrity of peer roles, ensuring that peers remain empowered within treatment systems rather than assimilated into clinical models.

Limitations within the literature suggest specific avenues for future research. While our review attempted to capture a range of implementation outcomes as described by Proctor et al. (2011), certain outcomes such as cost, adoption, penetration, and sustainability were not described or were underrepresented in the included studies, limiting conclusions on long-term scalability. Given the emerging evidence that PRS-delivered EBIs can be implemented with high feasibility, acceptability, and appropriateness, future research should prioritize the examination of these later-stage implementation outcomes. Despite limited availability of validated measures for outcomes like adoption, penetration, and sustainability (evidenced in a recent review of implementation outcome measures, Mettert et al., 2020), progress may be made by co-designing long-term implementation strategies with community partners and conducting more rigorous evaluation of these strategies. Studies should consider incorporating validated tools, such as the Program Sustainability Assessment Tool (PSAT), and related planning frameworks to evaluate and strengthen the sustained integration of PRS-delivered EBIs into service settings (Hall et al., 2021; Luke et al., 2014; Moreland-Russell et al., 2024). Future studies also should incorporate economic evaluations to assess the relative costs and benefits of PRS-led interventions compared to traditional service delivery models. Ongoing trials are beginning to address this gap, including two active peer-delivered behavioral activation trials that incorporate cost-effectiveness analyses (NCT05973838, NCT05933226, NCT06501781). Another major limitation is discrepancies in how implementation outcomes were measured across studies. Some studies relied on brief self-report scales rather than in-depth assessments, limiting the ability to capture variability in stakeholder experiences. While some articles employed validated instruments, others relied on single-item or brief, unvalidated measures of acceptability, feasibility, and appropriateness, which may not fully capture the complexity of these implementation constructs (Cuvillier et al., 2021; Wensing, 2021). A recent review has identified validated scales to assess these outcomes, including in substance use disorder contexts (see, Mettert et al., 2020), and resources such as the Implementation Outcome Repository (maintained by implementation research centers at King’s College London and University of East Anglia) provide detailed listings of available measures, including their psychometric properties, populations, and settings (Centre for Implementation Science at King’s College London et al., 2025). A guide on selecting implementation outcome measures has also been published by Stanford’s Center for Dissemination & Implementation (McGinty et al., 2024). Researchers could consider, as was done in some studies, setting and registering predefined trial benchmarks for implementation outcomes to support consistent interpretation (e.g., defining high fidelity as an average rating of ≥ 80% of content delivered as intended, or high acceptability as ≥ 75% of participants completing all intervention sessions.)Future research should also incorporate mixed methods approaches and longitudinal measurements to provide more robust assessments of intervention fidelity and impact over time. Finally, most included studies were conducted in high-resource settings, with limited representation of PRS-delivered EBIs from LMICs. Given that task-sharing models, including PRS-led interventions, have been widely implemented in LMICs to address workforce shortages in behavioral health, it is critical to expand implementation research in these settings (Satinsky et al., 2021). Implementation challenges in LMICs—such as limited infrastructure, variable regulatory environments, and cultural differences in PRS support models—may differ significantly from those in high-income countries. Future studies should prioritize research in diverse global contexts to ensure that PRS-led interventions are adaptable and scalable across health systems.

The shifting of behavioral EBI delivery from clinical staff to PRS reflects a broader movement in healthcare to expand access and bridge critical gaps in treatment (Grant et al., 2018). PRS bring a unique advantage. Their lived experience with SUD fosters trust, engagement, and relatability that traditional providers may struggle to achieve. This review, grounded in an implementation science framework, highlights both the promise and the challenges of PRS-led interventions. While PRS-delivered EBIs were found to be highly acceptable, feasible, and appropriate, their success hinges on structured training, institutional integration, and sustained support. Results underscore the need for research that examines long-term sustainability, cost-effectiveness, and system-wide strategies to optimize PRS integration.

Supplementary Material

Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/s10488-025-01470-x.