Public involvement in mental health research enhances research quality. The use of citizen science methods in mental health research has been described as a conclusion of a movement towards increased public involvement; however, this field is in its early stages of development. Our objective was to create a theory of change (ToC) for how citizen science can be used to enhance mental health research quality.

Iterative consultation with the stakeholders of an existing citizen mental health science study, that is, change for citizen science to achieve co-production at scale (C-STACS: https://www.researchintorecovery.com/research/c-stacs/)

We co-developed a ToC through an iterative consultation with C-STACS stakeholders who were (a) representatives of mental health community organisations (n=10), individuals with public involvement experience (n=2) and researchers (n=5). In keeping with established ToC practice, entities were identified, including long-term impacts, outcomes needed to create an impact, stakeholder assumptions and indicators for tracking progress.

A desired primary long-term impact of greater co-production of research was identified between researchers and members of the public, which would create a secondary impact of enhancing public capacity to engage in citizen mental health science. We proposed long-term outcomes needed to enable this impact: (1) greater co-production of research objectives and pathways between researcher and the public, (2) greater embedment of citizen mental health science into funder processes (eg, the creation of specific funding calls for citizen mental health science proposals, (3) greater clarity on the boundaries between citizen science and other participatory approaches (eg, so that there is not loss of impact due to conceptual confusion between these, (4) increased knowledge around effective frameworks to enable mass public participation and (5) greater availability of technology platforms, enabling safe and accessible engagement with citizen mental health science projects.

The proposed ToC is grounded in the C-STACS project, but intended to be broadly applicable. It allows the continued formation of a community of practice around citizen mental health science and should be reviewed, as greater knowledge is developed on how citizen mental health science creates change.