Table 3 Summary of study characteristic of included trials, including details of peer worker/s

Depression & Anxiety

Ellis et al. (2011)

Australia

39;

77%

female, 23% male

19.67 (1.66); range 18–25

University Students experiencing low-to-moderate depression & anxiety

3 × 1-h sessions over 3 weeks working through the content of the MoodGarden website:

a. Tools for self-management

b. Bulletins on lifestyle management

c. Discussions on effective treatments

d. Messageboard for peer-based support

e. Blogs and Charts

1. MoodGym

Five modules of online CBT:

a. Introduction to CBT

b. Reducing dysfunctional thinking

c. Overcoming negative feelings

d. Identifying stress and relaxation

e. Problem-solving strategies and enhancing relationships

Control: No intervention

Lived experience with a mood disorder

Not reported

Conley et al. (2020)

USA

118;

82.2% female,

17.8% male

20.8 (4.99); range

18 or older

University Students who identify experiencing a mental health illness/ challenge

4 × 2–3-h sessions

a. Consider the pros and cons of disclosing

b. There are different ways to disclose

c. Telling your story

d. Booster Session: Check-in about whether participants have chosen to disclose

Control: Waitlist control

University Student with lived experience of a mental health illness or challenge

Peer facilitators completed two days of training in the HOP-C manual

Mulfinger et al. (2018)

Germany

98;

69% female, non-binary not reported

15.75 (1.15); range 13–18

Inpatients and outpatients with Anxiety and/or Depression

3 × 2-h weekly sessions over 3 weeks of Honest, Open, Proud (HOP):

Themes:

a. Challenging beliefs or self-stigma

b. Pros & cons of disclosure

c. The right person

d. Telling one’s story

e. Role of solidarity and peer support

Workbooks contained vignettes, first-person accounts, worksheets, tables and role-plays

1 young expert and 1 young peer worker

Control: TAU

Young adult peer with lived experience of mental illness

Peer facilitators were trained by researchers and conducted a practice session

First Episode Psychosis

Alvarez-Jimenez et al. (2021)

Australia

170;

47.1% female, 52.9% male

20.91 (2.88); range 16–27

Young people in recovery of First Episode Psychosis, exiting early intervention service

Mean number of individual posts and/or comments = 21.49 (SD = 41.71) over 18 months (Mean = 8.15 (SD = 5.65)) of Online Social Network:

a. Icebreakers

b. user-generated threads

c. content related to mental health

d. content of general interest

Vocational training:

a. Ask the expert

b. individualized online vocational support

Online Therapy w/ health professional:

a. Online pathways – distinct themes on recovery

b. Online Steps—interactive therapy modules

Control: TAU

Peer workers had lived experience of mental illness

Not reported

Prevention of Eating Disorders

Becker et al. (2010)

USA

102;

100%

female

18.73 (0.72); range 18–21

University students (Freshman or Sophomore)

2 × 2-h sessions over

2 weeks of Cognitive Dissonance:

a. Group discussions on the thin ideal

b. Group brainstorming on cost of the thin ideal

c. Homework body appreciation

d. Role-plays on resisting the thin ideal

e. Shared lived experiences from peer-leaders and peers in the sessions

1.Media Advocacy:

a. Watch videos

b. Group discussions of the thin ideal

c. Group brainstorming on cost of the thin ideal

d. Food and exercise diaries

Peer-leaders with past participation in the program and a member or the sorority

4.5 h experiential training sessions. Peer-leaders trained in teams (3 – 4 peer-leaders at a time)

Ciao et al. (2021)

USA

Trial 1

N = 98;

female 80%

male 14%

non-binary 6%

Trial 2 N = 141;

80% female

15% male

5% non-binary

Trial 1 20.39 (4.12); range 18–50

Trial 2

19.66 (2.53);

Range 18–36

University students interested

in a body acceptance program

2 × 2-h group sessions over 2 weeks of the ‘EVERYbody Project’ involving 4–9 participants

a. Group discussions

b. Role-play

c. Group activities

Trial 1: 1 × Expert-leader & 2 x peer-leaders

Trial 2: 3–4 × peer-leaders

Trial 1: Control: No intervention

Trial 2:

Video intervention

a. Watch videos

b. Reflective writing

Peer-leaders with past participation in the female program

Training followed protocol used in the peer-led ‘Body Project’

Trial 1

2 days of training (16 h)

Trial 2

2 days of training (16 h)

with discussion on group facilitation skills and role plays on difficult diverse situations

Kilpela et al. (2016)

USA

180;

62% female, 38% male

19.9 (1.2); range 18–23

University students

2 × 2-h sessions over 2 weeks of ‘Body Project’

a. Group discussions on the thin ideal contrasting healthy ideals, the origin of the thin ideal, past pressures

b. Group brainstorming on cost of the thin ideal and combating the thin ideal

c. Homework: body appreciation, writing to a young person, challenging own behaviour

d. Role-plays on resisting the thin ideal

e. Shared lived experiences from peer leaders and peers in the sessions

Control: Waitlist

Peer-leaders with past participation in the program

Trainer to Trainer method: Experienced peer leaders in the program trained new peer leaders over two days

Resendel et al. (2021)

Brazil

74;

100%

female

20.5 (2.02); range 18–30

University students

4 × 60-min sessions over 4 weeks of ‘Body Project’ led by two peer leaders

a. Group discussions on the thin ideal, body appreciation/concerns

b. Group brainstorming on the cost of the thin ideal

c. Homework sessions on body appreciation

d. Role-plays on resisting the thin ideal

e. Engaged in further body activism

Control: No intervention

Have experience in Intuitive Eating and past body image concerns and currently a university student

References the Body Project website: Therefore, training on the concept and rationale of the body project, in group discussions and role plays, using the manual for guidance. Possibly some practice runs with feedback from supervisors, but unclear from publication

Prevention in Substance Use

German et al. (2012)

Thailand

983;

27.3% female

72.7% male

Median 19 (IQR = 18–20); range 18–25

Used meth-amphetamine

& engaged

in sex at

least 3 times

in the last 3 months

7 × 1.5–2.5 h group session twice weekly over 1 month of ‘Peer Education’, in groups of 8–12 participants:

a. Drug use on individuals

b. Drug use and social influences

c. Drug use and sex

d. Drug use and risk behaviours

e. Family and community

f. Community project

g. Review and graduation

2 boosters (3 & 6-month mark)

7 × 1.5–2.5 h group session twice weekly over 1 month of ‘Life Skills’, in groups of 8–12 participants:

a. Understanding life

b. Decision making skills and old friends/new friends

c. Danger of drug use

d. Sexually infectious diseases

e. How important is stress?

f. Emotion management and life goals

g. Envelope of goodness and graduation

Network groups for participants in both Peer Education and Life Skills received no intervention

Early 20 s, participated in an earlier study as part of the ethnography team

Researchers trained peer facilitators in a 1 week long intensive training session on building a prosocial role and to increase positive communication and interactions with peers