Table 1.

Summary of evidence by themes from systematic review

Beneficial impacts

Initial stages of research: PPI helped identify relevant topics for the research agenda, assisted in prioritizing topics for the research agenda and provided pragmatic criticism of the research protocol in perceiving whether research was relevant or appropriate to users

Undertaking research: PPI helped assess the appropriateness, wording and timing of research instruments (e.g. questionnaires, interview schedules) to the community and helped adapt the language of the instruments and information to suit the lay audience. PPI also assisted with recruitment to the study and improved response rates. Furthermore, PPI helped gain deeper and more personal insights because of the rapport users had with participants

Analysis and write‐up: PPI helped ensure emerging themes and trends were interpreted from the user perspective as well as the academic researcher perspective, assisted in identifying relevant knowledge gaps, and final research reports benefited from being grounded in user experiences

Dissemination and implementation: PPI helped with the dissemination and implementation of research findings owing to the dedication to and influence of users to the community. Studies reported that dissemination was delivered in a more poignant and user‐friendly way

Challenging impacts

Initial stages of research: Studies indicated that PPI led to scientific and ethical conflict in protocol design, which may have been due to a lack of knowledge and understanding of PPI. PPI may lead to a tokenistic nature of users' involvement and can cause power struggles between researchers and users

Data collection stage of research: PPI studies have reported the difficulty in recruiting a diverse range and representative sample of users to a project, the difficulty in balancing traditional academic criteria for reliability and user perspectives in a protocol for research and the difficulty in maintaining user confidentiality within meetings, where users may discuss personal experiences

The challenges reported by researchers in running PPI focus groups included users influencing each other, which may result in an over‐emphasizing of particular problems; groups being dominated by strong characters and their perspectives; groups being overshadowed by personal experience stories, when the aim was to identify research topics, and groups seen as a forum to get other people to accept their understanding of the disease

Dissemination and implementation: PPI led to research findings being disseminated before the academic papers are published, thereby jeopardizing academic publication

Time and Cost: PPI led to increased time and cost owing to the practical aspects of planning and managing the user involvement in the research, the time and cost of building up relationships within the community and setting up user groups, the training and education for both users and researchers and the additional time needed for users to read and comment on documentation

PPI, patient and public involvement.