Barriers and enablers to implementing capacity-strengthening initiatives for public and patient involvement in mental health research: a scoping review protocol informed by the Consolidated Framework for Implementation Research

Impact of PPI on contributors, research outcomes, and service provision

Evidence of the impact of PPI use in health research seems to be strongest at the project level. Several reviews on health and mental health care show that PPI: improves recruitment and retention (Ennis & Wykes, 2013), enhances design and dissemination (Allen et al., 2020; Blackburn et al., 2018; Mockford et al., 2012), and empowers contributors by building confidence, ownership, and trust (Brett et al., 2014; Richmond et al., 2023). PPI contributors have reported creating positive relationships with healthcare services after traumatic experiences in the mental health system, and developing new collaborative partnerships as a result of their participation in various aspects of the research cycle (Allen et al., 2020).

At the service provision level, some evidence suggests positive outcomes for mental health services. A review of nine studies by Ezaydi et al. (2023) found that co-produced mental health services were associated with increased attendance, treatment completion, fewer hospitalisations, and greater trust in the services. In-depth involvement of service users sometimes led to structural or cultural changes with potential long-term effects. However, such studies remain rare, and most focus on short-term outcomes.

At the policy and systems level, evidence is much weaker. A scoping review of healthcare research by Baumann et al. (2022) found that most studies describing and evaluating PPI assessed the PPI process itself rather than long-term policy impacts. Werner et al. (2025) similarly highlighted the lack of data on systemic impacts of PPI in psychiatric research, attributing this to limited standardisation of PPI impact measures and a lack of studies explicitly designed to evaluate long-term effects.

This gap in evidence may stem from the fundamental issue of low levels of PPI/co-production utilisation in mental health-related research, highlighted by the relatively small number of studies deemed eligible in reviews (e.g. Ezaydi et al., 2023). In a scoping review by Gonzales and Jones (2024), only 2 out of the 23 studies that measured service user perspectives reported service user involvement in the actual study design or implementation. Furthermore, Chinsen et al. (2025)’s systematic review of co-design in mental health interventions with young people found that their involvement was largely marginal.

Challenges in implementing PPI in mental health research

One key challenge for PPI is the demand for narrow forms of evidence focused on standardised evaluation processes that simplify nuanced and heterogeneous experiences (Armstrong & Byrom, 2025) and thus may be inadequate in measuring how each PPI contributor shaped the methods, results, and impact of a study. A lack of fully embedded approaches, together with inadequate use and reporting of evaluation measures, limits PPI’s potential to drive larger-scale changes in health systems and research processes (Baumann et al., 2022; Biddle et al., 2021; Brotherdale et al., 2024; Mockford et al., 2012). Tokenism—superficial involvement that fails to provide decision-making opportunities or address power inequities (Brotherdale et al., 2024; Ocloo & Matthews, 2016; Ocloo et al., 2021; Pinfold et al., 2025; Richmond et al., 2023)—is another common barrier, reinforcing unequal relationships between service users and researchers. Power imbalances impede participation by encouraging an ‘us vs. them’ mentality through labelling (‘PPI members’ vs. ‘researchers’), compartmentalising tasks, creating a false sense of decision-making power, discouraging critique of academic viewpoints, and limiting contact with senior researchers (Allen et al., 2020; Richmond et al., 2023).

There are specific considerations for PPI in mental health research. For example, affective or cognitive effects of psychiatric medications may be brought to the forefront and impact PPI contribution in unforeseen ways. A systematic review linked sedatives such as benzodiazepines to impaired social cognition (Haime et al., 2021); echoing a meta-analysis associating them with deficits in working memory, processing speed, attention, and expressive language (Crowe & Stranks, 2018). Other medications, including certain types of antipsychotics, have also been associated with cognitive impairment (Haddad et al., 2023; Joshi et al., 2021). Such changes may influence contributors’ engagement, relationships, and preferred tasks in research projects. Navigating side effects can also form part of the “expertise” of PPI contributors when generating knowledge about relevant topics, such as the impact of iatrogenic harm (Okkenhaug et al., 2024).

Socio-emotional and cognitive effects arising from mental health difficulties also shape PPI contributors’ experiences. Low self-esteem, common both as a precursor to, and consequence of, mental health conditions, is linked to poorer wellbeing outcomes, while higher self-esteem is a protective factor (de la Barrera et al., 2022; Hilbert et al., 2019; Keane & Loades, 2017; Rizwan & Ahmad, 2015). In PPI contexts, medication effects may converge with these socio-emotional and cognitive effects, producing varied impacts at individual, group, and project levels (Allen et al., 2020; Richmond et al., 2023)—it is important for research teams to consider how these experiences can in fact provide unique insight into topics being studied.

Stigma further undermines participation, and researchers holding stigmatising beliefs about the abilities of people with mental health difficulties has been widely documented (Allen et al., 2020; Biddle et al., 2021; Evans & Papoulias, 2020; Paul & Holt, 2017; Richmond et al., 2023; Susanti et al., 2020; Wadman et al., 2019). While teams often support PPI in principle, they may emphasise the ‘risks’ of close collaboration. One study noted that “Poor health, especially mental health, was recognized as a significant barrier to effective co-production,” though some clinicians acknowledged the need for extra support (Holland-Hart et al., 2019, p. 96). Institutional processes can also deter participation, as illustrated by a lived experience research assistant who described being compelled to disclose highly sensitive personal information during Human Resource procedures, finding the process “distressing and re-traumatising” (Richmond et al., 2023, p. 224).

Another dimension of stigma is the privileging of academic over experiential knowledge, reinforcing the ‘us vs. them’ divide, and deepening epistemic injustice. Rose and Kalathil (2019) explore this issue within mental health research, arguing that within current academic contexts, “co-production between professionals and service users is fundamentally an unequal relationship” (Rose & Kalathil, 2019, p. 8). Given the automatic privileging of academic or ‘rational’ forms of knowledge production in these settings, knowledge stemming from lived experience enters the field at a disadvantage. Paul and Holt (2017) observed that “The value placed on experiential knowledge vs. knowledge held within the research community emerged as a particularly complicated aspect of PPI in practice” (Paul & Holt, 2017, p. 7). Addressing this injustice in the long term requires not just individual- or team-level strategies, but systemic reconstruction involving a re-evaluation of the very principles underpinning mental health research.

Capacity-strengthening for PPI in mental health research

It is evident that unique barriers arise when implementing PPI in mental health research. Yet little attention has been given to the state of scientific knowledge on PPI capacity strengthening in mental health research that can address these. Research capacity strengthening is defined by Centre for Capacity Research and Science for Africa Foundation (2024) as “enhancing the capacity of individuals and organisations to conduct, manage, share and apply research, while enabling national and sub-national research systems to effectively support both research and the linkages between research and practice.”. It is considered a long-term process that can be applied at the individual, institutional, or national level, and can be applied to improving the quality of PPI in mental health research. Several studies on PPI in research have highlighted the lack of, and need for, targeted training of PPI contributors, and point to skill-building activities (Brett et al., 2014; Holland-Hart et al., 2019; Ocloo et al., 2021; Opie et al., 2023; Paul & Holt, 2017; Susanti et al., 2020). An important gap in training for PPI contributors is in research literacy (Allen et al., 2020; Bedenik et al., 2025). Tailored training for mental health research PPI contributors may help reduce tokenism, offer support in the ‘emotional work of using one’s lived experience identity, enhance skills sharing and support relationship building across research teams; and enhance comprehension and prevent overload from technical information (Allen et al., 2020; Capobianco et al., 2023; Werner et al., 2025). In a rapid review of training programmes for lived experience workforces, an analysis of 26 studies found that specialised, mental health-related training programmes resulted in improvements in confidence, communication skills, reflective listening, problem-solving, and overall improvements in job performance within the mental health services context (Opie et al., 2023). This points to the benefits that targeted capacity strengthening could bring to mental health research as well.

Moreover, implementation science provides tools to move PPI in mental health research beyond principles into practice by identifying the conditions that enable or hinder its meaningful adoption and sustainability. The Consolidated Framework for Implementation Research (CFIR; Damschroder et al., 2022) is particularly useful for examining how organisational culture, leadership, resources, and external policy drivers shape the extent to which PPI is embedded and valued within mental health research systems. CFIR comprises five overarching ‘domains’ indicating the systemic level at which a barrier or enabler sits (i.e., the innovation design itself, the outer setting, the inner setting, the individual level, and the implementation process). Each of these domains also contains several sub-constructs (39 in total) into which barriers and enablers are categorised. This framework has been successfully adapted for social science and health research over the years, including in some recent scoping/systematic reviews in the area of mental health (Garavito et al., 2023; Higgins et al., 2020; Le et al., 2022; Mutschler et al., 2022; Piat et al., 2021; Rangachari et al., 2022; Roshan et al., 2025).

Considering that there is no standardised guidance on what the capacity strengthening of PPI contributors in mental health research should look like, this scoping review aims to describe existing training programmes, onboarding activities, and other skill-building initiatives directed at PPI members in this area, and identify and categorise barriers and enablers to implementing these initiatives.

PPI contribution

A PPI panel of seven members, ranging from people with lived experiences of mental health difficulties, family members/carers, and public representatives, has been involved in the development of this protocol, and will be regularly consulted for the data synthesis and write-up of the review. The broader VISTA research programme is underpinned by this PPI panel, with each panelist embedded in one of the project’s work packages. As part of VISTA’s PPI process, before beginning to work together on research, the PPI panellists and academics underwent an induction phase involving capacity-strengthening activities such as team-building, crafting a personal narrative around recovery and mental health, consensus-building, influencing, and research literacy training.

Eligibility criteria

Eligibility criteria for literature to be included is detailed in Table 1. The review uses a slightly modified version of the JBI’s PCC framework (participants, concept, context), with the addition of outcomes as a final criterion to accommodate the review’s focus on barriers and enablers. In this review, concept will encompass any capacity-strengthening initiatives (such as training, webinars, educational materials, or workshops) that have been used with PPI contributors as the primary target in the research study.

Literature and resources dealing with mental health research will be considered; these sources must pertain to adults who are lived experience PPI contributors. Studies in which over 50% of PPI contributors are under 18 years of age will be excluded. Additionally, sources must also describe, to a meaningful extent, the upskilling, training, or capacity-strengthening of PPI contributors, and this capacity-strengthening should be aimed at enhancing the engagement of the PPI contributors in research projects (e.g. research literacy modules/manuals, ethics and data protection training, public speaking and presentation skills). Lastly, we will consider literature that indicates, implicitly or explicitly, barriers and enablers relating to the implementation of these capacity-strengthening initiatives. We will not consider: sources that do not have a mental health focus; sources that do not pertain to lived experience PPI members; sources that do not describe any capacity-strengthening initiatives; sources whose capacity-strengthening attempts are not at least partially targeted towards PPI contributors; sources whose upskilling/capacity-strengthening is not aimed at the enhancement of co-production capabilities; and sources that do not mention or allude to barriers or enablers relating specifically to the capacity-strengthening initiatives.

The review will screen published and unpublished literature that addresses the review’s aims, and will include quantitative, qualitative, and mixed methods designs. Systematic reviews, scoping reviews, umbrella reviews, and meta-analyses will be excluded; however, their reference lists will be manually checked for relevant primary sources. Conference proceedings, papers, and presentations will be excluded. A grey literature strategy (described below) will also be used, as it is expected that much of the relevant details on specific training for PPI contributors and research teams will be found in guidelines, training materials, and other community-based and non-peer reviewed sources.

The scope of what the review would consider under mental health research, as well as the preferred terminology to use in this area, was decided on in consultation with VISTA’s lived experience PPI team members. The phrase ‘mental health difficulty’ was seen by both researchers and lived experiences contributors as the most comprehensive and least stigmatising term to use through this review and is the term used in the ‘Sharing the Vision’ (Department of Health, 2020) policy. We will consider research dealing with any of the mental and behavioural difficulties outlined in the International Classification of Diseases—11^th Revision (ICD-11) (World Health Organisation, 2022).

Search strategy & information sources

The concepts comprising the search strategy include: PPI/Lived Experience, Mental Health, and Specific Capacity-Strengthening Initiatives. After the research team compiled lists of terms found in the literature for each concept, the study librarian selected the most relevant terms to include in the search string (outlined in Table 2)—this search string was then modified for the following databases: MEDLINE (EBSCOhost), Embase (Elsevier), PsycINFO (EBSCOhost), and CINAHL (EBSCOhost). The search did not have language, geographical, or time limitations to obtain all relevant studies. The search will be limited to studies published in English. Before commencing the data extraction stage, one of the researchers (SAV) will hand-search the reference lists of included studies to check for any additional studies that may meet the inclusion criteria.

Grey literature will be obtained through multiple avenues. Firstly, websites of key national and international PPI-related community, healthcare, and research organisations, and related materials such as guidelines or standards published by them, will be assessed for relevant information. Examples of such organisations are PPI Ignite, INVOLVE, the McPin Foundation, PPI-related web pages of national health systems such as the HSE and NHS, and blogs of lived experience PPI contributors and researchers. Secondly, sources such as unpublished theses (via open university repositories) and journal editorials will be considered. Lastly, key stakeholders working in the PPI space (such as prominent lived experience/PPI advocates, lived experience researchers, experts in the field of co-production, and other key community members) will be contacted directly to source additional, potentially unpublished resources on capacity-strengthening.

Screening

Database search results will be uploaded onto Covidence (Covidence systematic review software, 2025), where duplicates will be removed, and further screening will take place. At the title and abstract level, all references will be screened by two independent reviewers. Full texts will also be reviewed independently by two reviewers, and reasons for excluding articles will be recorded and used in the PRISMA flow chart. At each of these stages, screening will first be pilot-tested on 20% of the studies before continuing; conflicts between reviewers will then be closely monitored, and regular conflict resolution meetings between the reviewers will take place to resolve them—if needed, a third person from the team will be invited to resolve the conflict. If a significant number of conflicts arise during these first two stages, a further 10% of articles will undergo pilot-testing. Regular meetings will be held with the review team to ensure that there is a standardised approach to screening.

Data extraction

Data extraction will occur via the extraction function on Covidence; once data is initially extracted there, it will be transferred to NVivo (Lumivero, 2024), and if needed, on Microsoft Excel (Microsoft Corporation, 2025). Here, additional descriptive and thematic analyses will be performed. The JBI data extraction template has been modified to address review objectives 1 and 2 (Appendix A). The template will capture the studies’ descriptive information (e.g., authors and year of publication, country, study design, aim), population characteristics (e.g., sample size and type, age range, and description of the research team) details of the intervention (e.g., details of the capacity-strengthening initiatives, gaps in training identified, any PPI monitoring or evaluation tools used), context (e.g., mental health area/difficulty, challenges identified relating to mental health needs of PPI contributors). This set of data addresses aims one and two of the review.

Data relevant to the review’s third aim (identifying barriers and enablers) will be collected in line with CFIR; Appendix C; Damschroder et al., 2022). This review will structure significant information relating to the implementation of PPI capacity-strengthening initiatives according to the 39 constructs of CFIR, thereby extracting specific pieces of data that can be more easily translated for use in future implementation projects. The data extraction template (Appendix A) will first be pilot tested on 20% of studies by two independent reviewers before being used for the remaining studies, with regular discussions between the reviewers to resolve any problems with the template or major differences in the extracted data. In case the template must be revised, the amended template will be reflected in the published scoping review.

Analysis and presentation of findings

Data synthesis will occur in NVivo (and Excel as needed). Scoping review findings will be presented in line with JBI and PRISMA-ScR guidelines (Peters et al., 2020; Pollock et al., 2022; Tricco et al., 2018). A descriptive narrative account of the existing quantitative, qualitative, and mixed methods literature will be provided; augmented by tables that provide an overview of included study characteristics and methodologies used. Findings will focus on mapping, summarising, and charting available evidence; identifying knowledge gaps; clarifying concepts; and reviewing research conduct. This account will clarify how the scoping review results relate to, and address, its research aims. To achieve this, for aim 1 (capacity-strengthening initiative content and implementation processes) and aim 2 (outcome measures), a basic descriptive analysis will be conducted. For aim 3 (implementation barriers and enablers), data will be analysed deductively by mapping individual study findings to the CFIR.

Limitations

While the review takes steps to achieve comprehensiveness, some limitations still arise. Firstly, as this is a scoping review (rather than a systematic review), quality and risk-of-bias assessments will not be conducted. Additionally, we expect a large portion of the literature that will be analysed will be derived from non-peer reviewed or unpublished sources such as websites and documentation of community-level initiatives. Combined with the restriction to English-only literature, these limitations will reduce the extent to which the review’s findings can be used as an evidence base for policy or clinical guidelines. Furthermore, given the decentralised nature of the non-peer reviewed sources, and the review’s use of subject matter experts in identifying grey literature, some relevant resources may be missed in the literature search, particularly those that may not yet be published. Despite the limitations, this review will mark the first time that capacity-strengthening for PPI in mental health research contexts has been examined in a systematic way, and will springboard to support PPI capacity-strengthening both within and beyond the VISTA programme.