Experiential peer support and desistance from crime: a systematic realist literature review

Figures & data

Figure 1. Initial Programme Theory.

Figure 2. Flowchart of Literature Selection Process.

Table 1. In- and Exclusion Criteria.

Inclusion criteria	Exclusion criteria
Published between 1990 and April 2020 in English-language journals.	Published before 1990 and/or in non-English-language journals.
Intervention is experiential peer support or experiential peer support is the central element of the intervention.	Other intervention that does not include experiential peer support.
Intervention focused on achieving desistance(-supportive outcomes).	Intervention focused on improving participants’ physical health.
Asymmetry in the relationship between provider and recipient.	Mutual help groups or interventions in prison where provider is still incarcerated.
The support is at least partly provided one-on-one.	Group interventions.
All or a majority of EPs and clients have a background in criminal behaviour and/or a criminal justice history.	Minority of EPs and/or of clients have a background in criminal behaviour and/or a criminal justice history.

Table 2. Characteristics Included Studies.

Author (year)	Location	Quantitative/ qualitative	Design	Study population	Role of EP and type of intervention	Setting	Training for EPs	Rigour and relevance assessment	Potential limitations for this review
Adams and Lincoln (2020)	United States	Mixed-methods → qualitative part	Survey, interviews with EPs, interviews with stakeholders	EPs; survey (n = 25) and interviews (n = 16, mean age 49)	Forensic peer specialist	Several organisations (unknown)	Yes	Rigour = moderate Relevance = moderate	Internal validity: limited information on data collection and recording and data analysis. Reliability: findings not always supported by data.
Barrenger et al. (2017)	United States	Qualitative	Phenomenological life history interviewing	EPs (peer specialists, n = 15, 85%−87% male)	8 peer specialist/advocate/ counsellor, 2 peer respite workers; 2 health care navigators or coaches; 2 service coordinators; 1 case manager.	Several organisations (unknown)	Yes	Rigour = moderate Relevance = low	Internal validity: limited information on data collection and recording. Not 1 specific intervention being studied. Not all recipients have criminal background.
Barrenger et al. (2019)								Rigour = high Relevance = low
Buck (2014)	United Kingdom	Qualitative	Semi-structured interviews and observations	EPs (peer mentors, n = 18), mentees (n = 20), mentoring coordinators (n = 4) and probation staff (n = 2).	Several peer mentoring settings: probation-based project, care leavers’ service, women’s employment project, young women’s service. Group and individual interventions.	Several mentoring settings	Yes		External validity: possible sampling bias. Reliability: analysis by single researcher. Internal validity: limited information on data collection. Not all providers and recipients have a criminal justice background. In one of the projects the relationship does not seem asymmetrical.
Buck (2017)
Buck (2018)
Buck (2019a)
Buck (2019b)
Cos et al. (2020)	United States	Quantitative	One-group pretest-posttest design (baseline – 6 months)	Clients (n = 305; mean age 47.3; 71.7% male, 28.2% female, 0.1% transgender)	Peer recovery specialists providing services to individuals with substance use disorder.	Health Centre	Yes	Rigour = moderate Relevance = moderate	Internal validity: intervention was not only EPS. No control group, no adjustment for confounders. Not all providers have criminal background.
Creaney (2018)	United Kingdom	Qualitative	Semi-structured interviews	Children (n = 20) and professionals (n = 20)	Peer mentoring: study about potential of peer mentoring in youth justice system	N/A	N/A	Rigour = moderate Relevance = moderate	Not 1 specific intervention being studied. Study about the potential of experiential peer support in the youth justice system. Internal validity: limited information on data collection and recording and data analysis. Reliability: analysis by single researcher.
Harrod (2019)	United States	Qualitative	Semi-structured interviews (for clients: initial and follow-up interview)	EPs (n = 14) and clients (n = 9)	Peer mentors for transitional job employees	Social enterprise	Yes	Rigour = moderate Relevance = high	External validity: limited information on participant selection. Internal validity: limited information on data analysis; intervention was not only EPS. Reliability: analysis by single researcher. Limited description of intervention and EPs.
Hodgson et al. (2019)	United Kingdom	Qualitative	Participatory research & semi-structured interviews	EPs (n = 2, 25–30 years) & staff members (n = 4)	Peer mentoring for 16- to 25-year-olds involved in serious offending behaviours. Individual intervention.	Community project	Yes	Rigour = high Relevance = moderate	Transferability: small sample. Conflict of interest: one researcher worked at the project. Limited description of intervention and EPs. Focus on mechanisms and outcomes for EPs, not clients.
Jardine and Whyte (2013)	United Kingdom (Scotland)		Social return on investment study	N/A	Life Coaches offering support to short-term prisoners and after release.	Prison and community.	Unknown	N/A	Limited description of intervention.
Kavanagh and Borrill (2013)	United Kingdom	Qualitative	Semi-structured interviews	EPs (n = 8, mean age 36)	Mentoring for offenders in prison and/or after release. Individual intervention.	Projects that mentors offenders in prison and/or after release	Yes	Rigour = moderate Relevance = high	Transferability: small sample. Internal validity: limited information on data collection and analysis. Focus on mechanisms and outcomes for EPs, not clients.
Lopez-Humphreys and Teater (2019)	United States	Qualitative	Focus groups	EPs (n = 11, 9 male, 45% older than 45)			Yes	Rigour = moderate Relevance = moderate	Not 1 specific intervention being studied, study is about training for peer mentors.
Marlow et al. (2015)	United States	Mixed-methods → qualitative part	Single group pretest-posttest design & semi-structured interviews	Clients (n = 13, mean age 41, men).	Peer mentoring for parolees released from prison within last 30 days. Individual intervention.	Community-based	Yes	Rigour = moderate Relevance = high	Internal validity: limited information on data collection and analysis. Conflict of interest: one researcher knew three participants before their entry into the programme.
Matthews et al. (2019)	United States	Qualitative	Participant observation, interviews, focus groups	Staff (n = 10, 5 female, majority 30–65 years); observations n = 12 clients (students); interviews n = 18 (8 recent graduates, 10 former graduates)	Peer support to assist formerly incarcerated individuals reentering the community.	Job training programme	Unknown	Rigour = high Relevance = low	Internal validity: intervention was not only EPS. Limited description of EPs. Not all providers and recipients have criminal background.
Nixon (2020)	United Kingdom	Qualitative	Interviews	EPs (n = 19) and staff (n = 3)	Probation peer mentors, criminal justice drugs team mentors and health trainers. Individual intervention.	Community-based	Yes	Rigour = moderate Relevance = moderate	Internal validity: limited information on data collection and analysis. Reliability: analysis by single researcher. Limited description of intervention and EPs. Focus on mechanisms and outcomes for EPs, not clients.
Nyamathi et al. (2016)	United States	Quantitative	Randomised controlled trial. 3 conditions: - Intensive peer coaching and nursing case management - Intensive peer coaching Usual care (minimal peer coaching and nurse involvement)	Clients (n = 453 at 6-month follow-up, n = 529 at 12-month follow-up, men) Based on RCT (n = 600)	Peer coaching aimed at hepatitis A and B vaccine series completion for homeless men recently released on parole. Individual intervention.	Residential drug treatment facility	Yes	Rigour = moderate Relevance = high	Internal validity: intervention was not only EPS. Limited description of EPs.
Nyamathi et al. (2016)				Clients (n = 501 at 6-month follow-up, n = 529 at 12-month follow-up, men) Based on RCT (n = 600)
Portillo et al. (2017)	United States	Qualitative	Multiple method: - Review of available case files of each client - Observation and interviews with staff members Focus groups with current and former clients	Clients (case files n = 69, 61 male, 6 female, 2 unspecified; focus groups n = 15, 13 male, 2 female, aged 20-60) & staff members (2 EPs and 4 non-EPs; 2 male, 4 female)	Services provided by i.a. peer navigators for people with mental illness or emotional impairment, who are/were incarcerated and are within 90 days of discharge. Individual intervention.	Community project working with clients who are or were incarcerated.	Unknown	Rigour = moderate Relevance = high	Internal validity: intervention was not only EPS; limited information on data analysis. Limited description of EPs.
Reingle Gonzalez et al. (2019)	United States	Qualitative	Interviews (3 months into the programme and 6 months later)	EPs (peer reentry specialists, n = 7, 6 female) and clients (n = 3, 2 male)	Peer reentry specialists providing services to individuals with mental health problems.	Jail and upon release	Yes	Rigour = high Relevance = high	External validity: limited information on participant selection.
Sells et al. (2020)	United States	Quantitative	Pilot randomised controlled trial. 2 conditions: - Standard services - Standard services + peer mentoring	Clients (male, mean age 42.55, control group (n = 18), peer mentoring group (n = 39))	Peer mentoring for men released from incarceration with high risk for criminal re-offense.	Various programmes	Yes	Rigour = moderate Relevance = high	External validity: limited information on participant selection, limited sample size Internal validity: intervention was not only EPS.
Thomas et al. (2019)	United States	Qualitative	Interviews, chart review	Clients (n = 13; ages 26-61, women)	Community health workers providing support to female re-entering clinic patients (from jail and prison).	Primary care clinic	Yes	Rigour = high Relevance = high	Internal validity: intervention was not only EPS. Limited description of EPs.
Woodall et al. (2015)	United Kingdom	Qualitative	Discussion groups	Delegates representing a variety of organisations and research team (n = 58).	Formalized peer-based support services for prisoners aimed at improving their health. Group and individual interventions.	Several correctional settings	Unknown		Expert evidence, not substantiated with other data. Main focus on mechanisms and outcomes for EPs.

Table 3. Main Findings with Regard to Mechanisms.

Empathy and acceptance	EPs have a more profound or true understanding of clients’ situations and experiences (Barrenger et al., 2017; Barrenger et al., 2019; Nixon, 2020; Thomas et al., 2019) EPs have a non-judgmental attitude (Barrenger et al., 2017; Barrenger et al., 2019; Buck, 2018; Buck, 2019a; Creaney, 2018; Harrod, 2019; Matthews et al., 2019; Thomas et al., 2019)
Social learning	EPs act as role models (Barrenger et al., 2017; Barrenger et al., 2019; Harrod, 2019; Marlow et al., 2015; Portillo et al., 2017) Personal experiences make EPs more credible (Harrod, 2019; Reingle Gonzalez et al., 2019) Personal experiences make EPs less credible (Buck, 2017) Clients are inspired to become EPs themselves (Buck, 2017; Creaney, 2018; Nixon, 2020)
Social bonding	Trust and confidentiality are important in the EP-client relationship (Barrenger et al., 2017; Harrod, 2019; Kavanagh & Borrill, 2013; Matthews et al., 2019; Thomas et al., 2019) Shared experiences contribute to trusting relationship (Barrenger et al., 2019; Creaney, 2018; Matthews et al., 2019) Shared experiences contribute to easier contact or closer bond between EPs and clients (Barrenger et al., 2017; Barrenger et al., 2019; Buck, 2019a; Creaney, 2018; Harrod, 2019; Kavanagh & Borrill, 2013; Matthews et al., 2019; Portillo et al., 2017; Reingle Gonzalez et00A0;al., 2019)
Social control	Corrections by EPs are more easily accepted (Buck, 2018; Matthews et al., 2019) Importance of nondirective (Barrenger et al., 2019; Buck, 2018) and non-contemptuous approach by EPs (Harrod, 2019)
Narrative and identity formation	Clients can practice their new identities and received praise (Creaney, 2018) EPs can provide reassurance in clients’ identity transition (Buck, 2019a)
Hope and perspective	EPs provide inspiration and hope (Buck, 2014; Marlow et al., 2015; Nixon, 2020; Portillo et al., 2017) EPs demonstrate that change is possible (Barrenger et al., 2019; Buck, 2017; Buck, 2019a; Creaney, 2018; Kavanagh & Borrill, 2013; Matthews et al., 2019)
Translation and connection	EPs act as intermediary between clients and staff (Barrenger et al., 2019; Hodgson et al., 2019) EPs help clients navigating the system and connect them to other services and resources (Barrenger et al., 2017; Harrod, 2019; Marlow et al., 2015; Matthews et al., 2019; Portillo et al., 2017; Reingle Gonzalez et al., 2019; Thomas et al., 2019)
Recovery perspective	EPs understand desistance as a complex, non-linear process (Barrenger et al., 2019; Buck, 2018; Reingle Gonzalez et al., 2019) Importance of agency and empowerment by EPs (Buck, 2017; Buck, 2018; Thomas et al., 2019)

Table 4. Main Findings with Regard to Outcomes.

Act desistance	No decrease in criminal behaviour (Jardine & Whyte, 2013; Nyamathi et al., 2016) Possible decrease in criminal behaviour (Harrod, 2019; Sells et al., 2020)
Positive personal development	Increase in self-esteem and skills (Marlow et al., 2015; Matthews et al., 2019) Attitudinal and behavioural transformations (Thomas et al., 2019)
Improved mental health	No effect on drug use (Nyamathi et al., 2016; Nyamathi et al., 2016) Reduction in substance abuse and depression and anxiety symptoms (Cos et al., 2020)
Positive changes in personal circumstances	Improvement in clients’ stability (school enrolment, employment, housing) (Cos et al., 2020; Kavanagh & Borrill, 2013; Marlow et al., 2015; Matthews et al., 2019; Reingle Gonzalez et al., 2019) No effect on employment status (Nyamathi et al., 2016)
Increased social capital	Difficulties improving clients’ social network (Reingle Gonzalez et al., 2019)

Figure 3. Revised Programme Theory. Note. For mechanisms, outcomes and contextual factors displayed in grey we did not find sufficient evidence. The underlined mechanism of ‘Recovery perspective’ is the result of the inductive coding.

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