Violence and abuse are endemic globally. In the most recent Crime Survey in England and Wales, 2% reported past-year community violence (where most victims were men). Domestic violence or abuse (physical, sexual, psychological, economic and controlling or coercive behaviour) in the last year was reported by 7.5% of women and 4.3% of men, with victims of repeated or severe domestic violence and/or sexual violence more likely to be women. Most previous mental health research has neglected the impact of domestic and sexual violence on mental health and well-being, so our network will prioritise these, and their links with childhood experiences, and mental health in childhood and adulthood. We know that people with mental health problems are more likely to be victims of domestic or sexual violence, or have witnessed parental violence as a child; some mental health problems are also, much less commonly, associated with committing violent acts though there is very little known about this in relation to domestic violence perpetration. The UK government has recognised that preventing and reducing the impact of domestic and sexual violence and abuse is an important way to improve mental health. This network aims to reduce the prevalence of mental health problems among children, working age adults, and the elderly, by bringing together experts with different ways of thinking about violence, abuse and mental health - some will have personal experience of these issues, others will have expertise from the work that they do, and survivor researchers have expertise born of lived experience and their work. Understanding, preventing and reducing the impact of violence and abuse on mental health requires that we resolve problems that have prevented progress in the past. Firstly, different organisations mean different things when they talk about violence and abuse. This has meant that violence and abuse, and mental health, are measured in different ways by different organisations, and that information collected about violence and abuse does not tell us what we need to know. For example, mental health surveys sometimes ask about violence, but do not ask about the relationship between the victim or perpetrator, what type of violence was experienced, or how it impacted on mental health. Secondly, we have limited knowledge of how and why experiencing different types of violence and abuse increases the risk of developing mental disorders, or how new digital technologies are changing people's experiences of abuse and how this impacts on mental health. Thirdly, we do not have interventions that are effective in preventing or reducing violence experienced by people with mental health problems, or programmes that reduce the risk of mental health problems developing after experiences of violence or abuse. Network activities will address these challenges through: 1) working with people who have personal experience of violence, abuse, and mental health problems to learn from different perspectives, and generate fresh ideas and research questions, with a focus on the commonest types of violence- domestic and sexual violence and abuse; 2) trying to answer research questions through small grant competitions, workshops, conferences, and other events; some of these will lead to larger grant applications; 3) sharing measurement approaches, including how to ethically and safely research this area, which will help data collection and analysis by health services, the criminal justice system, family courts, social care, charities, and researchers. We will also develop an online resource providing information about datasets that can be used in research in the future. We aim to make our results known by publicising them widely through our network and other organisations, including policy makers within NHS England, Public Health England and the National Institute for Health and Social Care Excellence, technology companies and the general public.

PROJECT APPROACH The C-STACS project will bring citizen science approaches to mental health. CHALLENGE: CITIZEN SCIENCE IS NEW TO MENTAL HEALTH Citizen science approaches have not yet been used at scale in mental health. We reviewed citizen science platforms. UK-based Zooniverse has no active, paused or finished mental health-related projects. EU-based eu-citizen.science has one project (CoAct) which includes mental health as one of several global concerns being addressed. USA-based scistarter.org has one project (neureka) using gamification for dementia research. The citizen science projects related to health which do exist typically involve biological and physical health research (e.g. www.cellslider.net, 100forParkinsons App, Colony B App). A more general internet search for citizen science and mental health identifies a few specific studies, e.g. the Emotional Brain Study addressing neuropsychological aspects of mental health and the MH2K Oldham project involving a youth-led approach to mental health, both in the UK, and the Games X Mental Health study exploring interactions between people with mental health problems and their informal carers in Spain. Two citizen science projects have taken place in the UK in relation to the overlapping area of wellbeing: the Secrets of Happiness study which ran in 2018 and has not published results, and the Great British Wellbeing Survey running in 2020. In relation to new projects, no mental health studies were funded as a UKRI Citizen Science Exploration Grant. Turning to publications, again very little has been written about citizen science and mental health. The 2020 ECSA report on characteristics of citizen science provides a useful foundation but no mental health specific guidance. A 2020 overview report by RAND Europe on emerging developments in citizen science identified the potential for new types of health research, such as personal health tracking / n-of-1 studies, but with no mention of mental health. A 2018 paper (https://doi.org/10.1093/heapro/daw086) on citizen science applied to public health provides a useful typology of project characteristics: Aims (investigation, education, collective good, action), Approaches (extreme, participatory science, distributed intelligence, crowd sourcing) and Size (local, mass). Our project will be mass participatory science, with aims of collective good (WP2) and action (WP3). Other papers have used citizen science in cognate areas, e.g. urban stress (https://doi.org/10.1057/s41599-020-0460-1). A 2019 position paper locates citizen science in relation to health research (https://doi.org/10.1080/15265161.2019.1619859), noting the connection with participatory action research and community-based participatory research traditions, and identifies community-driven 'n-of-we' studies which align with the current proposal. The paper also discusses general ethical issues of citizen science in health research, including consent, participation risks/benefits, data ownership and attribution, which have informed the WP1 focus on these issues. Finally, a search of the 'Citizen Science' journal identified one paper (https://doi.org/10.5334/cstp.184) discussing patient partners in health research. WORK PACKAGES (WPs) WP1 develops a theoretical foundation for citizen science in mental health, and prepares for WP2 and WP3. Mental health has a very established tradition of public involvement, coproduction and peer-led research, and mapping between mental health and citizen science constructs will be a key project output. WPs 2 and 3 address specific challenges outlined in the case for support, using Zooniverse as an online platform to support mass participation. WP2 creates new knowledge about supporting mental health recovery and WP3 about how people living with mental health problems actually look after themselves. WP4 mobilises the findings from WPs 1 to 3 to maximise impact.