Peer Recovery Support Services and Recovery Coaching for Substance Use Disorder: A Systematic Review

Abstract

Purpose of Review

In this article, we systematically review the research on peer recovery support services (PRSS) for substance use disorder (SUD).

Recent Findings

We update our 2019 review on PRSS for SUD, with a focus on quantitative, multi-group studies (K = 28; N = 12,601). We searched four databases (December 2024), identifying 17 new studies reviewed here in addition to 11 studies included in our previous review. Though challenges with synthesis of this diverse literature remain, evidence has coalesced to indicate the capacity of PRSS to improve SUD treatment engagement and retention, with some preliminary but inconclusive evidence suggesting PRSS may also support better substance use outcomes.

Summary

PRSS can play an important role in the SUD care continuum, particularly in helping individuals initiate and stay engaged with treatment. More work is needed, however, to determine when, where, and over what duration PRSS are most impactful, as well as for whom, and under what conditions PRSS are most beneficial.

Introduction

The past decade has seen the rapid uptake and study of peer recovery support services (PRSS) across the continuum of substance use disorder (SUD) care, with the recent Global Position Paper on Recovery recommending, “Recovery representation in the design, delivery, and evaluation of all addiction-related polices and service practices…” [1]. We have previously described PRSS as peer-driven mentoring, education, and support ministrations delivered by individuals who, as a result of their own experience with SUD and SUD recovery are experientially qualified to support peers with SUD and commonly co-occurring mental disorders [2]. In addition to their lived experience, most PRSS also undergo varying degrees of professionally led PRSS-specific training that provide role and boundary definitions, and advice intended to enhance quality of care. PRSS are also notable for their emphasis on long-term engagement with recovery support services (RSS) through mobilization of personal, familial, and community help, without allegiance to specific treatment modalities or recovery pathways [3, 4]. Although PRSS owe their origin to non-professional, unpaid, mutual-help models of peer support (e.g., Alcoholics Anonymous), they are considered distinct given their more explicit training, and professional deployment in clinical and public health settings.

In a previous systematic review of the quantitative literature on PRSS for SUD, we highlighted the potential benefit of peer supports in a range of SUD treatment settings [2]. Ultimately, we concluded that although PRSS appear to support individuals’ SUD recovery efforts in a wide range of settings, more work was needed to establish the efficacy of this class of support services, and to clarify the role of PRSS providers across SUD treatment settings.

While our previous 2019 review included all PRSS related studies, including those with less rigorous single-group and cross-sectional designs, the significant growth of this literature now affords a review focused on studies with greater methodological rigor that can best inform theory and practice. In this updated systematic review, we have included all multi-group studies to date (i.e., randomized controlled trials, muti-group prospective and retrospective studies), including those described in our initial review. We summarize clinical findings by key outcomes: 1) Linkage to treatment, treatment engagement, treatment readmission, and 2) substance use.

Method

Search

We conducted a systematic search of the literature through PubMed, EMBASE, CINAHL, and PsycInfo (as of December 23, 2024, with no date restrictions), using the search terms “recovery coaching”, “peer recovery support”, “peer-based recovery support services”, and “individual peer support” in combination with substance use terms (see specific syntax in Appendix A). We operationally defined PRSS as services or ministrations delivered by individuals with lived experience of SUD and SUD recovery providing structured RSS, with the goal of supporting service recipients’ recovery from SUD and co-occurring disorders. Articles had to contain at least one substance use or other SUD recovery-relevant outcome. Studies of any SUD and of all ages were included. Due to resource limitations, reports published in languages other than English were not identified.

Data Extraction

The search identified 360 references across four publicly available databases. We included randomized controlled trials (RCTs), and multi-group prospective and retrospective studies of PRSS related to SUD. Thirty-seven additional references were later identified through reference harvesting of relevant review articles and also screened for eligibility. Articles were screened and assessed for inclusion by three reviewers (authors JBO, SSG, MRK) using the Covidence platform, with the PRISMA flow chart shown in Fig. 1. Covidence identified and removed 175 duplicate records. One additional record was identified as a duplicate during review, resulting in 221 records screened for eligibility on title/abstract. After a review of title/abstracts, an additional 182 publications not meeting inclusion criteria were removed (e.g., book chapters and conference abstracts; studies that did not report quantitative outcomes), leaving 39 publications for full text assessment. A full text review removed another 22 articles, including 7 review articles that were reference harvested for potentially relevant citations before exclusion. Seventeen articles remained for data extraction, to which we added 11 articles published before June 2019 included in our previous review that were not identified in the present search, leaving 28 publications included in this updated review.

Fig. 1.

Our search identified 360 references across four publicly available databases (i.e., PubMed, EMBASE, CINAHL, and PsycInfo). We included randomized controlled trials (RCTs), and multi-group prospective and retrospective studies of peer recovery support services (PRSS) related to substance use disorder (SUD). Thirty-seven additional references were later identified through reference harvesting of relevant review articles and also screened for eligibility. Articles were screened and assessed for inclusion by three reviewers (authors JBO, SSG, MRK) using the Covidence platform. Covidence identified and removed 175 duplicate records. One additional record was identified as a duplicate during review, resulting in 221 records screened for eligibility on title/abstract. After a review of title/abstracts, an additional 182 publications not meeting inclusion criteria were removed, leaving 39 publications for full text assessment. A full text review removed another 22 articles, including 7 review articles that were reference harvested for potentially relevant citations before exclusion. Seventeen articles remained for data extraction, to which we added 11 articles published before June 2019 included in our previous review that were not identified in the present search, leaving 28 publications included in this updated review. PRISMA flow diagram created with PRISMA2020 [5]

From these articles, we identified and note in Table 1: 1) the study design, 2) the nature of the intervention/s, 3) the intervention’s length, 4) the population studied, 5) the sample size, 6) sample sex, race/ethnicity, and age characteristics, 7) the length of the study’s observation/follow-up period, 8) the study’s retention rate, 9) the primary substance/s taken, and 10) the main study outcomes.

Table 1.

Reviewed peer recovery support services papers showing study description, demographics, retention, and primary outcomes

				Sample
Article	Study design	Intervention(s)	Intervention length	Sample description	Size (N)	Sex	Race/ethnicity	Mean Age (SD)	Observation period	Retention rate	Primary substance	Substance use and related outcomes
Beaudoin et el., 2022 [6]	Randomized controlled trial	Exp: Emergency department behavioral intervention delivered by a peer recovery specialist with 90 days follow-up support Con: Emergency department behavioral intervention delivered by licensed clinical social worker	90 days	Adults with OUD	N = 648	F = 32%, M = 68%	White 67%, Black 6%, Mixed, Other 10%, biracial, or multiracial 9%, American Indian or Alaska Native 3%, Native Hawaiian or Other Pacific Islander 0.5%, Asian 0.5%	36.9 (10.8)	18 months	N/A	Opioids	A substantial proportion of participants engaged in SUD treatment within 30 days of their index emergency department visit, however, groups were not significantly different in rates of treatment engagement
Belanger et al., 2024 [7]	Multi-group retrospective	Exp: Residents receiving an intensive recovery support intervention Con: Residents not receiving intensive recovery support intervention	30 days	Individuals entering certified Level II and III SUD recovery residences	N = 175	F = 36%, M = 64%	White 71%, other races not reported	36.3 (SD not reported)	6 months	N/A	Multi-substance	Residents receiving intensive recovery support intervention had greater retention rates, reduced likelihood of disengagement, and more growth in recovery capital after living in SUD recovery housing for 6–9 months
Belenko et al., 2021 [8]	Randomized controlled trial	Exp: PRSS + services as usual Con: Services as usual	1–25 phone or in-person contacts	Adults in a drug court program	N = 76	F = 20%, M = 80%	Black non-Hispanic 53%, White non-Hispanic 42%, Hispanic 32%	27.5 (SD not provided	9 months	93%	Multi-substance	Participants receiving PRSS had less rearrests and better drug court engagement relative to controls. No group differences were observed for substance use recurrence or treatment engagement
Bernstein et al., 2005 [9]	Randomized controlled trial	Exp: A single, structured encounter targeting cessation of drug use, conducted by peer educators in the context of a routine medical visit Con: Written advice only	Single session (range 10–45 min)	Out of treatment adults with past 90-day cocaine and/or heroin use attending hospital walk-in clinic	N = 1,175	F = 29%, M = 71%	Black non-Hispanic 62%, White non-Hispanic 14%, Hispanic 23%, Other < 1%	38.0 (8.3)	3 and 6 months	66%	Multi-substance	Compared to controls, at 6-month follow-up, participants receiving a brief peer-support intervention were more likely to be abstinent from cocaine, and trended toward greater heroin, and both cocaine and heroin abstinence (p = 0.05). A trend was also observed in bioassay measured cocaine use, but not heroin use. No group differences were noted in medically managed withdrawal or treatment admissions among those who were abstinent. Those receiving the peer-support intervention demonstrated a trend toward greater reductions in addiction and medical severity
Blondell et al., 2008 [10]	Multi-group prospective	Exp: A single, 30–60-min session in which peers in SUD recovery shared their personal experience with patients to provide emotional support, enhance motivation to maintain abstinence, and encourage the patient to attend inpatient treatment and/or mutual-help groups after medically managed withdrawal discharge Con: No peer intervention	Single session	Patients, hospitalized for alcohol and other drug medically managed withdrawal	N = 119	F = 38%, M = 62%	White 83%, Black 12%, Hispanic 4%, Other < 1%	40.0 (13.0)	1 week	83%	Multi-substance	Participants who received a single, 30–60-min peer counseling session were more likely to report that they had attended mutual-help group meetings during the first week following medically managed withdrawal discharge. Trends were also observed in terms of those receiving peer counseling being more likely to remain abstinent from all substances, and also initiate professional aftercare treatment
Boisvert et al., 2008 [11]	Multi-group prospective	Exp: Peer Support Community Program: In a long-term supportive housing community, select individuals are taught to help govern the community and provide ongoing psychosocial support to fellow residents Con: A sample of residents living in the same long-term supportive housing community the year prior to instigation of the Peer Support Community Program	Open ended	Adults living in permanent supportive housing following inpatient SUD treatment	N = 18	Participants’ sex not reported	Not reported	Not reported	1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 months	12.5%	Multi-substance	Pre- to post-intervention, participants in the Peer Support Community Program reported more emotional, informational, tangible and affectionate support. Participants in the Peer Support Community Program also had lower relapse rates over the study period compared to a sample of residents living in the permanent supportive housing setting the year prior to instigation of the peer-support program
Byrne et al., 2020 [12]	Randomized controlled trial	Exp: Physician-initiated recovery coaching intervention + treatment as usual Con: Treatment as usual only	6 months	Individuals with SUD recruited during hospitalization for SUD complications	N = 98	F = 41%, M = 59%	Caucasian 80%, African American 16%, Hispanic 2%, Other 2%	42.2 (10.7)	6 months	71%	Multi-substance	Compared with treatment as usual alone, recovery coaching was associated with greater SUD treatment engagement over the 90-day study period, and at 6-month follow-up. No between group differences were observed in substance use frequency, or self-reported physical or mental health
Chambers et al., 2024 [13]	Randomized controlled trial	Exp: Behavioral intervention from PRSS Con: Behavioral intervention from licensed clinical social worker	90 days	Emergency department patients experiencing opioid overdose, complications of opioid use disorder, or a recent history of opioid overdose	N = 648	F = 32%, M = 68%	White 69%, Other 10, mixed, biracial or multi-racial 9%, Black, African, Haitian or Cape Verdean 6%, unknown 3%, Hispanic 17%	36.9 (10.8)	18 months	100%	Opioids	Between-group differences in opioid overdose were not statically significantly different over the 18-month monitoring period
Cupp et al., 2022 [14]	Randomized controlled trial	Exp: Inpatient peer recovery coach linkage and follow-up contact for 6 months Con: Usual care only (providing contact information for SUD resources and peer-recovery coaches)	6 months	Inpatient adults with SUD	N = 193	F = 40%, M = 60%	Caucasian 80%, African American 16%, Hispanic 3%, Other 2%	41.7 (10.3)	6 months	25%	Multi-substance	Participants receiving linkage to recovery coaching had a decrease in mental/behavioral emergency department visits from pre- to post-intervention, but not mental/behavioral inpatient encounters or medical emergency or inpatient encounters. There was no significant difference in 30-day acute care readmissions
Deering et al., 2011 [15]	Multi-group prospective	Exp: The Mobile Access Project Van: A peer-based mobile service providing a safe place for female sex-workers to rest and eat, and for staff to provide peer-support, condoms and clean syringes, while also acting as a point of contact for referrals to health services Con: A comparable sample of female sex-workers who did not utilize the mobile outreach program	Up to 18 months	Female sex-workers who use alcohol and other drugs	N = 242	F = 100%	Caucasian 51%, Aboriginal ancestry 43%, Other 7%	36.0 (median; interquartile range, 26.0–41.0)	18 months	Not reported	Multi-substance	Women were more likely to utilize the Mobile Access Project Van if they were at higher risk (i.e., seeing < 10 clients per week, and/or working in isolated settings, injecting cocaine or injecting/smoking methamphetamine in past 6 months), and were also more likely to access the intervention’s drop-in center. Past 6-month use of the peer-led outreach program was also associated with a four-fold increase in the likelihood of participants utilizing inpatient SUD treatment including detox and residential SUD treatment
Hutchison et al., 2023 [16]	Multi-group retrospective	Exp: Peer support services delivered in community outpatient SUD treatment clinics Con: Matched controls receiving outpatient SUD services without peer support	90 days	Medicaid-enrolled adults 18–64	N = 1,047	F = 41%, M = 59%	European American 82%, Other 18%, 3% Hispanic	Not reported	90 days	N/A	Multi-substance	Those receiving peer support had lower acute care utilization during intervention but were equivocal on other measures of outpatient care utilization to controls. Over 90-day follow-up, those receiving peer support showed an increase in inpatient treatment utilization while controls showed a decrease
James et al., 2014 [17]	Multi-group prospective	Exp: Parents participating in the Families FIRST program + PRSS Con: Parents participating in the Families FIRST program only	60 days	Parents and caregivers referred by child protective services to a substance use outpatient treatment program	N = 1,362	F = 76%, M = 24%	Caucasian/White 81%, Hispanic/Latino 30%, Black/African American 9%	28.6 (27.5)	36 months	32%	Multi-substance	PRSS was associated with faster outreach, and shorter latency to initial clinical assessment (d = 0.16), and higher rates of any treatment service initiation compared to no peer contact. Those receiving PRSS were less likely to complete treatment, however, among those completing treatment, the average length of treatment was significantly greater for the PRSS +TAU group than controls (d = 0.35). Participants receiving PRSS who discontinued treatment remained in treatment longer than controls who
Klein et al., 1998 [18]	Multi-group retrospective	Exp: Individuals participating in the Friends Connection program. A 6-month peer-led social support program including intensive case management Con: Individuals receiving community care as usual	6 months	Adults identified by the City of Philadelphia that have a history of frequent, long-term, psychiatric hospitalizations. 100% had current AUD or other SUD	N = 61	F = 26%, M = 74%	African American 76%, Caucasian 19%, Hispanic 5%	40.0 (SD not reported)	Variable (up to 2.5 years)	N/A	Multi-substance	Individuals participating in the program had fewer crisis events and hospitalizations over follow-up, with increased social functioning and quality of life relative to controls
Mills Huffnagle et al., 2022 [19]	Multi-group retrospective	Exp: Individuals with opioid use disorder receiving buprenorphine and peer recovery support services Con: Individuals with opioid use disorder receiving only buprenorphine	Variable (average of 14 PRSS appointments attended)	Adults with opioid use disorder in outpatient care	N = 277	F = 42%, M = 58%	Caucasian 87%, African American 12%, Asian < 1%, Hispanic/Latine 9%	37.2 (11.5)	30 days	Not reported	Opioids	Patients receiving peer recovery support services attended more opioid use disorder medical appointments vs. those not receiving peer recovery support services
Min et al., 2007 [20]	Multi-group retrospective	Exp: Individuals enrolled in the Friends Connection Program: A community-based program in which participants are paired with a peer who has successfully achieved alcohol and other drug abstinence and is successfully coping with their mental health issues Con: A comparable community sample of individuals who did not participate in the Friends Connection Program	Variable (average 2.25 years)	Adults identified by the City of Philadelphia that have a history of frequent, long-term, psychiatric hospitalizations. 100% had current AUD or other SUD	N = 484	F = 35%, M = 65%	White 30%, Black 64%	37.7 (8.7)	3 years	N/A	Multi-substance	Compared to a demographically and diagnostically concordant comparison group, participants in the Friends Connection Program had longer periods of living in the community without rehospitalization, and a lower overall number of rehospitalizations over a 3-year monitoring period
O’Connell et al., 2020 [21]	Randomized controlled trial	Exp: Physician-initiated recovery coaching intervention + treatment as usual Con: Treatment as usual only	3 months	Individuals with SUD recruited during hospitalization for SUD complications	N = 137	F = 34%, M = 66%	African American 58%, White 20%, Other 12%, Hispanic 13%	37.9 (10.3)	9 months	47%	Multi-substance	Compared with treatment as usual alone, recovery coaching was associated with higher levels of relatedness, self-criticism, and outpatient service use at 3-, but not 9-month assessment. Recovery coaching was also associated with lower alcohol use at 9-month follow-up
Ray et al., 2021 [22]	Randomized controlled trial	Exp: Peer recovery coaching offering guidance, support, and coordination of treatment services, as well as $700 in vouchers to cover the cost of the additional recovery support services Con: Treatment as usual only	12 months	Individuals recently released from prison and enrolled in Public Advocates in Community Re-Entry (PACE), a non-profit organization providing community-based services to previously incarcerated people	N = 100	F = 42%, M = 58%	African-American 36%, White 60%, Multi-racial 4%, Hispanic 3%	38.5 (10.4)	12 months	33%	Multi-substance	Study attrition was high, however those who received peer recovery coach support had better SUD recovery outcomes, including improved self-reported mental and physical health and reductions in substance use. The treatment group also improved in terms of self-efficacy and treatment motivation
Rowe et al., 2007 [23]	Randomized controlled trial	Exp: A community-oriented group intervention with citizenship training and peer support combined with standard clinical treatment, including jail diversion services Con: Standard clinical treatment with jail diversion services only	Variable (mean 10.6 sessions)	Adult outpatients with severe mental illness who had criminal charges within the two years prior to study enrolment, 31% with alcohol use disorder, 42% with other SUD	N = 114	F = 32%, M = 68%	African-American 58%, Caucasian 31%, Native American 3%, Other 8%, Not to identify 1%, Hispanic 15%	39.8 (8.8)	6 and 12 months	61%	Multi-substance	Four months of ‘Citizenship Training’ geared toward social participation and community integration + peer mentorship, and standard clinical treatment including jail diversion services, produced reduced alcohol use over 12-month follow-up, while those receiving standard clinical treatment with jail diversion services alone demonstrated increased drinking over the same period. Both groups demonstrated significantly less non-alcohol drug use and fewer criminal justice charges over the 12-month follow-upperiod
Samuels et al., 2018 [24]	Multi-group retrospective	Group 1: ‘Lifespan Opioid Overdose Prevention’ (LOOP) program: The program provides opioid overdose patients presenting to two hospital emergency departments take-home naloxone, patient education on overdose rescue, and consultation with a community-based peer recovery coach for addiction treatment navigation Group 2: Take-home naloxone with print and video patient education materials about naloxone assembly and use, in addition to usual care consisting of medical stabilization and provision of a list of substance use treatment programs in printed discharge instructions Group 3: Usual care only	At least 90 days	Adults presenting to two hospital emergency departments with opioid overdose	N = 151	F = 33%, M = 68%	White 80%, Black 9%, Asian 1%, Other 10%	30.6 (median; interquartile range 25.1–45.5)	12 months	N/A	Opioids	At 12-month follow-up via medical chart review, groups were not significantly different in terms of proportion of participants initiating medication for opioid use disorder, number of times returning to the same emergency department for overdose, number of deaths, and median time to death
Sanders et al., 1998 [25]	Multi-group cross-sectional	Exp: Peer-led counseling providing comprehensive case management including counseling, support groups, and assistance with housing, transportation, parenting, nutrition and child welfare Con: Counseling from traditionally trained addiction counselors	Variable (mean 11 months)	Pregnant and postpartum women in recovery from crack cocaine addiction	N = 56	F = 100%	African American 66%, Hispanic 27%, Other 8%	31.5 (SD not reported)	N/A	N/A	Crack cocaine	Clients receiving ongoing counseling from a peer-counselor, compared to clients receiving counseling from traditionally trained addiction counselors were more likely to describe their counselors as empathic, to identify them as the most helpful aspect of the program, to utilize other clinic resources, and to more strongly recommend their program
Schutt et al., 2021 [26]	Randomized controlled trial	Exp: PRSS + Veteran’s Administration Supportive Housing Con: Veteran’s Administration Supportive Housing only	9 months	Military veterans who receiving Veteran’s Administration Supportive Housing accommodations identified by case managers or medical records as having a history of alcohol or other drug misuse and of a cooccurring mental illness	N = 166	F = 7%, M = 93%	Minority race 45%	52.8 (9.0)	9 months	Not reported	Multi-substance	Military veterans receiving PRSS utilized significantly more mental health services relative to controls
Smelson et al., 2013 [27]	Multi-group prospective	Exp: ‘Maintaining Independence and Sobriety through Systems Integration, Outreach, and Networking’ (MISSION) program, involving temporary housing, integrated mental health and SUD treatment, case management, and vocational and peer support Con:’s Administration TAU including temporary housing, medical treatment, consultation with a psychiatrist, group therapy, and vocational training	12 months	Military veterans with SUD co-occurring mental disorders who are unemployed and have experienced homelessness	N = 333	(F = 4%, M = 96%)	African American 62%, White 27%, Other 11%	46.5 (8.4)	6 and 12 months	70.6%	Multi-substance	In comparison to TAU, those receiving MISSION had greater outpatient session attendance within the 30 days before the 12-month follow up (d = 1.25), and a greater decline in the number of psychiatric hospitalization nights (d = –0.26). Both groups improved on measures of substance use and associated problems at 12 months, with those in MISSION less likely to drink to intoxication (OR = 0.29) and experience serious tension or anxiety (OR = 0.53)
Tracy et al., 2011 [28]	Randomized controlled trial	Exp: 1) Mentorship for Addictions Problems to Enhance Engagement to Treatment (MAP-Engage): A peer-driven intervention with open-ended individual peer contact and peer-led groups. Peers escort patients to first outpatient program 2) Dual Recovery Treatment + MAP-Engage: Dual Recovery Treatment is an intervention involving 8 weeks of clinician-delivered individual and group relapse prevention therapy Con: Treatment as usual only	8 weeks	Adult inpatients at Veteran’s Administration with high hospitalization recidivism and current and/or past diagnosis of SUD, and two or more past-year hospitalizations. 88% had current alcohol or other SUD in addition to psychiatric comorbidity	N = 96	F = 3%, M = 97%	African American or Black 57%, White 25%, Hispanic 13%, Native Hawaiian or Pacific Islander 1%, Other 4%	56.0 (8.0)	12 months	100%	Multi-substance	Compared with treatment as usual alone, MAP-Engage, and MAP-Engage + Dual Recovery Treatment were both associated with greater post-discharge, outpatient substance use treatment attendance, general medical, and mental health services appointment adherence, and greater utilization of inpatient substance use treatment services
Upadhyaya et al., 2021 [29]	Multi-group retrospective	Exp: Care through Engaging Patients in Care Coordination (EPICC), a peer recovery specialist-run treatment referral program Con: Usual care only	Single session with option of ad libitum follow-up	Patients with opioid use disorder admitted to hospital with injection drug use related infections	N = 334	F = 48%, M = 52%	African American 48%	39.3 (SD not reported)	90 days	N/A	Opioids	The all-cause 90-day readmission rate was significantly lower among patients referred to the EPICC PRSSS program relative to controls
Wakeman et al., 2019 [30]	Multi-group retrospective	Exp: Individuals receiving treatment at a primary care medical clinic that had implemented a multi-modal strategy that included forming interdisciplinary teams of local SUD recovery champions, access to SUD pharmacotherapy, counseling, and recovery coaching Con: Individuals receiving treatment at standard primary care medical clinics that could refer patients to an SUD treatment clinic offering pharmacotherapy and behavioral interventions	Variable (mean 0.35 recovery coach interactions)	Propensity score matched sample of adult, primary care patients with an SUD diagnosis matched on baseline treatment utilization	N = 2,706	F = 39%, M = 61%	Non-Hispanic white 83%	49.0 (15.0)	9 months	Not reported	Multi-substance	During the 9-month follow-up period, the experimental group had fewer inpatient days and emergency department visits, more primary care visits and buprenorphine and naltrexone prescribing
Watson et al., 2021 [31]	Multi-group retrospective	Exp: Emergency department patients receiving Project POINT, an emergency department-based intervention aimed at providing opioid overdose survivors with naloxone and recovery supports and connecting them to evidence-based medications for opioid use disorder Con: Emergency department patients not receiving Project POINT	Single session with variable after-support	Opioid poisoning survivors	N = 1,462	F = 44%, M = 56%	White 90%, Black 4%, Hispanic < 1%, Other 4%, Unknown 2%	37.5 (0.3)	N/A	N/A	Opioids	Patients receiving Project POINT intervention had a significant increase in medications for opioid use disorder prescriptions dispensed, non-opioid use disorder medication prescriptions dispensed, and naloxone access. There were no between group differences in subsequent drug poisoning-related hospital admissions
Watson et al., 2024 [32]	Randomized controlled trial	Exp: Emergency department patients receiving Project POINT, an emergency department-based intervention aimed at providing opioid overdose survivors with naloxone and recovery supports and connecting them to evidence-based medications for opioid use disorder Con: Emergency department patients not receiving Project POINT	Single session with variable after-support	Emergency department patients with opioid use related presenting problems	N = 243	F = 40%, M = 60%	White 88%, African American 12%	36.1 (10.9)	3, 6, and 12 months	83%	Opioids	No significant between group differences were observed between patients receiving the POINT intervention versus controls
Winhusen et al., 2020 [33]	Randomized controlled trial	Exp: Peer-recovery support services + personally tailored opioid overdose education and naloxone Con: Personally tailored opioid overdose education and naloxone only	20-min telephone intervention	Adults, primarily recruited from a syringe service program, with an opioid-positive urine drug screen + reporting treatment for an opioid overdose in the past 6 months	N = 80	F = 45%, M = 55%	African American 6%, Caucasian 80%, Other/Mixed 8%, Hispanic 3%	39.2 (11.4)	12 months	55%	Opioids	Participants receiving peer-recovery support services were less likely to have experienced an opioid overdose through 12-month follow-up. No between group differences were observed for opioid use through 12-month follow-up as measured by either opioid-positive urine drug tests or self-reported days of past month opioid use

PRSS peer recovery support services, RCT randomized controlled trial, TAU treatment as usual, SUD substance use disorder, SD standard deviation, Exp experimental group, Con control group, M male, F Female, AA Alcoholics Anonymous, N/A not applicable

Quality Assessment

We assessed risk of bias using the Quality Assessment Tool for Quantitative Studies by the Effective Public Health Practice Project [34]. Three bachelors-level trained reviewers (JBO, SSG, MRK) assessed each paper in duplicate, and reached consensus on component ratings before a global assessment was determined (i.e., strong, moderate, or weak).

Results

Results Overview

Our review of publications since the first empirical studies of PRSS in 1998, identified 13 RCTs, and 15 multi-group prospective or retrospective studies. This review includes 28 publications from 27 original, multi-group studies that altogether included 12,601 participants (females, 39%; males, 61%) Study observation periods ranged from 1 week to 3 years following PRSS intervention.

Study Quality

The 28 studies reviewed had variable quality (see Figs. 2 and 3). Approximately a third of the studies were rated as strong with low risk of bias (k = 11). Nine studies were rated moderate because of selection bias (k = 3), lack of reporting on withdrawals and dropouts (k = 3), the way potential confounders were addressed (k = 2), and use of non-validated/non-reliable measures (k = 1). Eight studies were rated weak with a high risk of bias due to selection bias (k = 7), the way potential confounders were addressed (k = 5), how withdrawals/dropouts were handled (k = 4), weak study design (k = 1), unblinded outcome assessors (k = 1), and the use of non-validated/non-reliable measures (k = 1).

Fig. 2.

Risk of bias for each individual study (k = 28) displayed with the Risk-of-bias VISualization (ROBVIS) tool [35]

Fig. 3.

Risk of bias summary across studies (k = 28) displayed with the Risk-of-bias VISualization (ROBVIS) tool [35]

Linkage to Treatment, Treatment Engagement, and Treatment Readmission Outcomes

Design Types and Rigor

PRSS are commonly employed in a range of medical, clinical, and community settings to help patients connect to, and remain in treatment. This section includes a total of 20 studies, of which 8 were RCTs, and 12 were multi-group prospective or retrospective. Sample sizes ranged from 61 to 2,950 and with follow-ups periods ranging from 1 week to 3 years.

Linkage to Treatment, Treatment Engagement, and Treatment Readmission Findings

Randomized Controlled Trials (RCTs)

In an RCT with military veterans receiving PRSS or treatment as usual (TAU) only, Tracy et al. [28] found that participants receiving PRSS were more likely to attend medical, mental health, and SUD treatment appointments (d = 0.41), and had more substance use related hospitalizations at 1-year follow-up (d = 0.44). Schutt and colleagues [26] also explored the utility PRSS for military veterans, integrating PRSS into the Veteran’s Administration Supportive Housing program. Participants receiving weekly PRSS had greater mental health service utilization during the 9-month treatment period. Byrne and colleagues’ [12] found that inpatient linkage to recovery coaching services for individuals hospitalized for medical issues related to SUD was associated with greater engagement in RSS at 30-day follow-up (84% vs. 34% for controls); at 6-month follow-up, 80% of participants who received recovery coaching were still engaged with RSS compared to only 24% of those in the control group (d = 15.77), though these differences did not translate into reduced substance use. In an RCT testing peer recovery coaching’s capacity to decrease acute care utilization, Cupp and colleagues [14] found that linking inpatients to peer coaches who supported them for 6 months post-discharge was associated with a significant decrease in mental and behavioral emergency department visits (OR = − 2.62).

Some null RCT findings have also been reported in this domain. Winhusen et al. [33] conducted an RCT evaluating a single 20-min telephone-delivered PRSS intervention for increasing medication for opioid use disorder (MOUD) enrollment and decreasing overdose risk in individuals primarily recruited from a syringe service program [33]. They found that although participants receiving PRSS were significantly less likely to report an overdose in the following year, rates for initiating MOUD were not significantly better. In a follow-up RCT extending the work of Watson et al. [31], the researchers found no effect of their emergency department PRSS intervention on re-presentation to the emergency department, MOUD linkage, inpatient admission, or overdose mortality [32]. And in an RCT testing the utility of PRSS added to drug court services as usual, versus services as usual only, Belenko et al. [8] found no effect on treatment engagement over a 9-month monitoring period, though participants receiving PRSS were less likely to reoffend. Additionally, while Beaudoin and colleagues found that around 30% of people receiving a referral to SUD treatment from an emergency department intervention delivered by either a peer recovery specialist or clinical social worker ended up engaging with treatment, engagement rates didn’t differ significantly by group [6].

Multi‑group Prospective and Retrospective Designs

In a multi-group retrospective study of PRSS for individuals with SUD and co-occurring mental disorders, Klein and colleagues [18] found that relative to individuals receiving usual community-based care, program participants had fewer crisis events (d = –0.97) and hospitalizations (d = –1.07). The same program was investigated by Min et al. [20], who found that program participants had longer periods of living in the community without rehospitalization, and a lower overall number of rehospitalizations over a 3-year monitoring period. Then, in a multi-group cross-sectional study of a peer-led mobile outreach program for street-based female sex workers, Deering and colleagues [15] found that past 6-month use of the peer-led outreach program was associated with a four-fold increase in the likelihood of participants utilizing inpatient SUD treatment, including medically managed withdrawal and residential SUD care. Working with military veterans with SUD and co-occurring mental disorders who were experiencing homelessness, Smelson and colleagues [27] assessed a novel peer-led program providing case management, temporary housing, integrated mental health and SUD treatment, and vocational support. Veterans receiving this intervention had greater outpatient session attendance within the 30 days before the 12-month follow up (d = 1.25), and a greater decline in the number of psychiatric hospitalization nights (d = − 0.26). More recently, in a retrospective study of a peer recovery specialist-run treatment referral program, Upadhyaya et al. [29] found that engagement with PRSS by individuals with opioid use disorder admitted to hospital with injection drug use related infections was associated with 56% lower odds of all-cause readmission within the 90 days following engagement care contact.

Trends and mixed findings have also been reported. Blondell et al. [10] found that 100% of medically managed withdrawal facility patients receiving a brief peer visit and consultation initiated professional aftercare treatment, versus 82% for treatment as usual controls (p = 0.06). James and colleagues [17] found that parents involved in child protective services who also received PRSS engaged in treatment services at a higher rate and more rapidly despite fewer outreach attempts, and remained engaged in treatment longer, compared to controls, however, controls had higher rates of treatment completion. In a retrospective cohort study of patients receiving care in primary care medical settings with and without integrated addiction treatment including pharmacotherapy and recovery coaching, Wakeman and colleagues [30] found that over their 15-month observation period, individuals receiving PRSS had more primary care visits, fewer inpatient days, and fewer emergency department visits. However, effect sizes were small, and the mean number of hospitalizations was similar between groups. In a multi-group retrospective study of people with opioid use disorder receiving or not receiving PRSS in an outpatient opioid treatment program, Mills Huffnagle and colleagues [19] observed that individuals receiving PRSS attended more medical appointments, though they did not have significantly different time in treatment versus controls. They did, however, note that length of time in treatment was a stronger positive predictor of number of medical appointments attended for non-PRSS patients relative to PRSS patients, suggesting PRSS may help individuals with less time in treatment engage with medical care. In a multi-group retrospective study testing a peer recovery coach driven emergency department-based intervention designed to provide opioid overdose survivors with MOUD and recovery supports, Watson et al. [31] reported that the intervention was associated with greater opioid use disorder and mental health medication prescription. There was, however, no significant effect related to subsequent overdose-related hospital admissions. Most recently, Hutchison and colleagues [16] found Medicaid-enrolled adults with SUD receiving peer support had lower acute care utilization during intervention but were generally equivocal on other measures of outpatient care utilization relative to controls. Over 90-day follow-up, those receiving peer support showed an increase in inpatient treatment utilization, versus controls who showed a decrease.

Null findings have also been reported. In a multi-group retrospective study, Samuels et al. [24] reviewed electronic medical records to explore if individuals receiving emergency department treatment for opioid poisoning benefit from PRSS + take home naloxone relative to take home naloxone only, or usual care consisting of medical stabilization and a list of SUD treatment programs at discharge. Groups were not different at 12-month follow-up in terms of initiating medication for opioid use disorder.

Summary of Linkage to Treatment, Treatment Engagement, and Treatment Readmission Findings

Twenty of the 28 reviewed publications reported on a linkage to treatment, treatment engagement, and treatment readmission related study outcome, 8 of which were RCTs. Of the 20 multi-group studies including at least one of these outcomes, 9 reported positive findings, including 4 RCTs, with promising results and/or identified sub-groups of participants most likely to respond well to PRSS. Five studies reported mixed results or trends, and 4 reported no advantage of PRSS relative to control conditions. Studies speak to the potential of PRSS provided in inpatient medical (3 studies), the Veteran’s Administration (3 studies), and community (5 studies) settings to increase or help maintain patients’ engagement with formal SUD treatment, but evidence to date for the capacity for PRSS to support treatment engagement in emergency departments is relatively weak (4 studies).

Substance Use Outcomes

Design Rigor

In addition to supporting linkage to treatment and treatment engagement, PRSS have the potential to affect substance use outcomes. This section includes a total of 12 studies, of which 8 were RCTs, and 4 were multi-group prospective or retrospective. Sample sizes ranged from 18 to 1,175 and with follow-up periods ranging from 1 week to 18 months.

Substance Use Findings

Randomized Controlled Trials (RCTs)

In an early PRSS RCT, Rowe et al. [23] found that four months of a peer mentorship program designed to support social and community integration in addition to standard clinical treatment that included jail diversion services, was associated with reductions in alcohol use over 12-month follow-up, while controls’ drinking increased. More recently, O’Connell and colleagues [21] found that skills training with a peer-led social engagement program for individuals recruited while receiving inpatient medical care was associated with reduced past- 30-day alcohol use at 9-month follow-up versus skills training only (d = 0.52).

Several RCTs have produced mixed findings. Bernstein and colleagues [9] found that participants receiving a structured encounter targeting cessation of drug use conducted by peer educators in the context of a routine medical visit were more likely to report being abstinent from cocaine 6 months post-intervention compared to controls receiving written advice only (d = 0.24). These results were however partially negated by urine toxicology testing, which did not fully support self-report outcomes. The experimental group also showed a non-significant trend toward greater opioid abstinence (40.2%) versus controls (30.6%). Winhusen and colleagues [33] found that a 20-min, telephone delivered PRSS intervention designed to increase MOUD engagement and reduce drug poisonings in people primarily recruited from a syringe service program reduced the likelihood of drug poisoning over 12-month follow-up, however, it did not significantly reduce opioid use.

Some trends have also been reported. Ray and colleagues [22] found that previously incarcerated individuals with SUD receiving 12 months of peer recovery coaching and community support saw a 14% reduction in alcohol and other drug use from baseline to 6-month assessment, while those receiving community support alone, saw a 15% increase. This study, however, had high participant attrition, with only 33% of participants completing 12-month assessment.

Negative findings have also been reported. In an RCT testing the utility of PRSS in addition to drug court services, versus services as usual only, groups were not significantly different on the percentage of positive or missed drug screens over a 9-month monitoring period [8]. Further, using follow-up data from Beaudoin and colleagues’ study [6], Chambers and colleagues [13] found that participants presenting to an emergency department with opioid related problems and randomized to receive PRSS were not significantly less likely to experience a subsequent opioid poisoning event over the18-month monitoring period relative to those randomized to receive support from a licensed clinical social worker. And Byrne and colleagues [12] found that inpatient linkage to recovery coaching services for individuals hospitalized for medical issues related to SUD was not associated with better post-discharge substance use outcomes, although PRSS was associated with better treatment retention.

Multi‑group Prospective and Retrospective Designs

Blondell et al. [10] found that individuals in inpatient medically managed withdrawal care receiving a single, 30–60 min peer mentoring session trended toward greater abstinence from all substances 7–10 days following discharge versus those that did not (84% vs. 59%, p = 0.06). Around the same time, Boisvert and colleagues found that participants in the Peer Support Community Program, a long-term, peer-run supportive housing community for adults living in permanent supportive housing following inpatient SUD treatment had lower substance use rates relative to controls, while also reporting more emotional, informational, tangible and affectionate support.

Some notable mixed findings have also been reported. Smelson et al. [27] tested PRSS for military veteran’s with SUD and cooccurring mental disorders, finding improved treatment engagement and reduced hospital readmission rates, with those receiving the PRSS intervention less likely to drink to intoxication (OR = 0.29) and experience serious tension or anxiety (OR = 0.53). However, PRSS did not outperform TAU in terms of substance use and associated problems at 12-month follow-up.

Negative findings have also been reported. In their study exploring an emergency department PRSS intervention that included take home naloxone, Samuels et al. [24] found no significant differences between patients receiving PRSS + take home naloxone, relative to controls in terms of number of times returning to the same emergency department with subsequent opioid poisoning, number of deaths, or median time to death.

Summary of Substance Use Findings

Twelve of the 28 reviewed publications reported on a substance use related study outcome, 8 of which were RCTs. Of the 12 multi-group studies exploring substance use outcomes, 4 produced positive findings, and 6 produced mixed findings or trends, with 8 of these studies being RCTs. In addition, 4 studies produced negative findings. Studies suggest PRSS may be most impactful on substance use outcomes when initiated in medical (5 studies) and community settings (4 studies), with one study also showing benefit in a drug court setting.

Discussion

Since our last review of the PRSS literature [2], the number of publications on this topic has more than tripled, reflecting the rapidly growing interest in this class of services and the wide range of settings PRSS are being utilized in. While this growing literature will continue to produce insights, presently, synthesis of findings remains challenging given the diverse range of PRSS interventions described with markedly differing levels of intervention intensity. PRSS services are often combined with formal interventions like psychotherapy and pharmacotherapy which adds additional complexity. Despite this, a sufficient body of results from rigorous multi-group studies signals several important findings.

Studies Examining Treatment Linkage and Engagement by PRSS Suggest Benefit

Taken together, the weight of evidence indicates a benefit of PRSS on treatment linkage and engagement across a range of inpatient and outpatient settings. This aligns with theoretical models of PRSS that posit that peers are uniquely positioned to establish credibility, and build rapport and trust with people with SUD, which is likely to increase individuals’ willingness to accept treatment recommendations and stay engaged with treatment when faced with challenges. Peers’ lived experience navigating treatment systems, often with first-hand knowledge of local treatment and recovery resources, mean they are also well positioned to help individuals navigate complicated and sometimes fraught treatment landscapes in ways other providers cannot.

Evidence for a Benefit of PRSS on Substance Use Outcomes is Less Compelling

Evidence to date is weaker for PRSS on substance use outcomes, with findings highlighting the need for more work to explore what kind of dose and under what conditions PRSS might influence substance use outcomes. Additionally, it will be important for future studies to explore any mechanisms through which benefits are conferred. While it is possible PRSS could directly influence substance use reduction or cessation through the emotional and behavioral support and pro-recovery modelling they provide, it is also possible improvements in substance use are secondary benefits of PRSS effects on other factors like treatment linkage and engagement.

PRSS Show Benefit Across a Range of Settings but may be more Potent in Some

PRSS specialists supported individuals with SUD across the continuum of care in the studies reviewed here. PRSS interventions have produced positive results both in terms of treatment engagement and retention, and substance use outcomes across a wide variety of settings, including inpatient medical units, the United States Veteran’s Administration, and recovery residences/support housing. The one setting where results have generally been less promising is emergency departments. This may be in part a result of the inherent challenges in supporting people with SUD presenting to emergency departments. PRSS-based interventions may not be sufficient to surmount these challenges. At the same time, any successes in connecting individuals to formal treatment from emergency departments could have significant positive public health implications and cost savings. Furthermore, emergency departments are often experienced as hostile and stigmatizing places by people with SUD, and PRSS may be valuable from a patient comfort perspective.

PRSS Effects do not Appear to Vary by Primary Drug

Most studies included in this review recruited samples with a range of primary substances and/or poly-substance use, yet a subset (k = 8) focused specifically on opioid use. No prima facie evidence of superiority of PRSS for one primary substance over another was found. At the same time, findings highlight the potential for PRSS specialists to support people with opioid use disorder in special ways, including helping individuals initiate MOUD. Additionally, given the unique stigma experienced by people with opioid use disorder, PRSS may be especially important for engaging and helping to retain this population in care.

PRSS Appear to Work as Stand‑alone Interventions or as a Complement to Existing Interventions

The studies reviewed here highlight the range of ways PRSS specialists provide services across settings, sometimes working as stand-alone interventionists, but more commonly working in a multidisciplinary treatment team or augmenting a clinical treatment. On balance, research to date suggests PRSS specialists have the potential to improve outcomes whether implemented as stand-alone interventions or as a complement to existing interventions/treatments. There may, however, be things PRSS specialists can do better stand-alone (e.g., linking patients to treatment) versus in tandem with other providers (e.g., reducing substance use lapses).

PRSS may Help Reduce Stigma in Clinical and Recovery Support Services Settings

Some evidence suggests PRSS may also have the potential to reduce stigma in clinical settings and the community [36–38]. This is not surprising given PRSS specialists are an embodiment of the idea that recovery is possible, challenging negative assumptions about people with addiction. Through their work in professional environments and the community, PRSS specialists also challenge antiquated moral models of addiction that proffer that people with addiction are inherently bad people.

PRSS Research has Improved over the past Six Years, but more Research is Needed to Clarify the Nature, Extent, and Duration of PRSS Impact

Many of the methodological limitations of the literature identified in 2019 remain, including challenges with distinguishing PRSS effects from co-delivered SUD treatments, heterogeneous populations, highly varying PRSS intervention durations and intensities, and varying roles and qualifications of peer workers. Some of these limitations are perhaps unavoidable given the diverse range of peer services offered in the field and the polythetic nature of SUD and its comorbidities. At the same time, many of these challenges can be overcome by targeted research.

In terms of bias risk, the fact the majority of articles in this review were of strong or moderate overall quality highlights the positive trend toward greater rigor in this growing literature. At the same time, the fact a significant subset of studies were rated as weak, draws attention to the need for more high-quality studies of PRSS.

Limitations, and Future Directions

Some limitations should be noted. 1) It is difficult to parse out the relative benefits of PRSS and concurrent treatments. Additional careful and scientifically rigorous evaluations of PRSS will help tease out these relative effects. 2) Presently, there is no agreed upon framework for categorizing PRSS interventions (e.g., talk-interventions versus assertive linkage). Future work is needed to develop such a framework – perhaps in line with the National Institutes of Health’s Science of Behavior Change initiative [39]. Such a framework would aid systematic examination of disparate PRSS interventions and support valid conclusions despite heterogeneity. 3) The studies reviewed here delivered PRSS at highly variable doses and durations. More work is needed to explore how PRSS interventions at differing delivery intensities and durations may influence relevant outcomes. 4) Many studies reviewed here utilized non-randomized designs vulnerable to sampling bias. More RCTs on PRSS are needed. 5) Most of the RCTs reviewed here did not use intent-to-treat design. It is possible that omitting treatment non-completers from analyses who may have dropped out because of a failure of care (i.e., attrition bias) produced an artificial false-positive benefit favoring the PRSS conditions. 6) Most studies focused on individuals with severe SUD and comorbidities, so it cannot be known how the findings reviewed here generalize to individuals with less severe SUD. 7) We considered including other SUD related outcomes in this review, including change motivation, positive and negative affect, criminal justice involvement, and recovery capital; however, to date there are insufficient rigorous studies speaking to these outcomes to warrant review. 8) Little is known about the relationship between peer worker job satisfaction, job tenure, and patient outcomes, and though preliminary findings suggest PRSS are associated with cost savings to health systems [40], future studies should address these knowledge gaps. 9) While the PRSS literature has grown substantially since our last review, the heterogeneity in samples, forms of measurement, and outcomes preclude meta-analysis at this time.

There are also limitations associated with this review. The protocol was not pre-registered, and from a global PRSS science perspective, there is potential for reporting bias given the focus on peer-reviewed and English language studies. Additionally, though papers were screened and assessed for bias in duplicate, due to resource constraints, study outcomes were not.

Conclusions

Taken together, the literature to date suggests PRSS are likely to improve treatment engagement and retention when added to existing continuums of care or included in existing interventions/treatments, though more work is needed to determine PRSS effects on substance use, and when, where, and over what duration PRSS are most impactful. More work is also needed to determine for whom, and under what conditions PRSS are most beneficial. Work informing how patient/PRSS matching in terms of demographics, primary substance, and chosen recovery pathway(s) affects outcomes will also be beneficial. In keeping with prior mutual-help program research [e.g., 41, 42], PRSS are likely to amplify and extend the benefits of more expensive clinical services in cost-effective ways, but little work has been reported on this, and cost-effectiveness analyses are needed [40]. In summary, evidence to date suggests PRSS can support SUD recovery, especially through helping individuals connect to and engage with treatment. Based on the corpus of research, treatment organizations and agencies may benefit from integrating PRSS into their models of SUD care.

Data Availability

No datasets were generated or analysed during the current study.

Supplementary Material

The online version contains supplementary material available at https://doi.org/10.1007/s40429-025-00645-8.