The effectiveness, implementation, and experiences of peer support approaches for mental health: a systematic umbrella review
Authors: Cooper Ruth E. , Saunders Katherine R. K. , Greenburgh Anna , Shah Prisha , Appleton Rebecca , Machin Karen , Jeynes Tamar , Barnett Phoebe , Allan Sophie M. , Griffiths Jessica , Stuart Ruth , Mitchell Lizzie , Chipp Beverley , Jeffreys Stephen , Lloyd-Evans Brynmor , Simpson Alan , Johnson Sonia 
Published: February 2024

Abstract
Background
Peer support for mental health is recommended across international policy guidance and provision. Our systematic umbrella review summarises evidence on the effectiveness, implementation, and experiences of paid peer support approaches for mental health.

Methods
We searched MEDLINE, EMBASE, PsycINFO, The Campbell Collaboration, and The Cochrane Database of Systematic Reviews (2012–2022) for reviews of paid peer support interventions for mental health. The AMSTAR2 assessed quality. Results were synthesised narratively, with implementation reported using the CFIR (Consolidated Framework for Implementation Research). The protocol was registered with PROSPERO (registration number: CRD42022362099).

Results
We included 35 reviews (426 primary studies, n = 95–40,927 participants): systematic reviews with (n = 13) or without (n = 13) meta-analysis, or with qualitative synthesis (n = 3), scoping reviews (n = 6). Most reviews were low or critically low (97%) quality, one review was high quality. Effectiveness was investigated in 23 reviews. Results were mixed; there was some evidence from meta-analyses that peer support may improve depression symptoms (particularly perinatal depression), self-efficacy, and recovery. Factors promoting successful implementation, investigated in 9 reviews, included adequate training and supervision, a recovery-oriented workplace, strong leadership, and a supportive and trusting workplace culture with effective collaboration. Barriers included lack of time, resources and funding, and lack of recognised peer support worker (PSW) certification. Experiences of peer support were explored in 11 reviews, with 3 overarching themes: (i) what the PSW role can bring, including recovery and improved wellbeing for service users and PSWs; (ii) confusion over the PSW role, including role ambiguity and unclear boundaries; and (iii) organisational challenges and impact, including low pay, negative non-peer staff attitudes, and lack of support and training.

Conclusions
Peer support may be effective at improving some clinical outcomes, self-efficacy, and recovery. Certain populations, e.g. perinatal populations, may especially benefit from peer support. Potential strategies to successfully implement PSWs include co-production, clearly defined PSW roles, a receptive hierarchical structure and staff, appropriate PSW and staff training with clinical and/or peer supervision alongside safeguarding. Services could benefit from clear, coproduced, setting specific implementation guidelines for PSW. PSW roles tend to be poorly defined and associations between PSW intervention content and impacts need further investigation. Future research should reflect the priorities of providers/service users involved in peer support.