BackgroundChile is implementing a Community Mental Health Model with a strong role of primary health care (PHC). PHC has great potential to early detection and provision of accessible and coordinated services to people who present mental illness and/or substance use issues (MISUI). However, stigma toward people with MISUI among PHC professionals is a significant barrier to accessing good quality of care. A wealth of literature supports the importance of reducing stigma for this population. The main goal of this research project is to determine the effectiveness of a comprehensive anti-stigma intervention in reducing stigmatizing attitudes and behaviors among PHC providers toward individuals with MISUI in the Chilean context, using Centros de Salud Familiar (CESFAMs) as the point of intervention.MethodsThe intervention is based on an initiative that was previously developed in Canada and then also pilot-tested in Lima, Peru, with the Center for Addiction and Mental Health (Ontario, Canada). The model will be culturally adapted with CESFAM PHC provider and user inputs to be relevant and valid to Chile. The 18-month intervention includes five (5) components that are simultaneously implemented in CESFAMs: (1) Develop a Team of Local Champions in each intervention CESFAM, comprising PHC providers and users; (2) Analysis of Internal CESFAM Policies, Procedures, and Protocols to determine areas of improvement in service delivery for individuals with MISUI; (3) Raising Awareness of stigma toward MISUI using various forms of media within the CESFAM; (4) Innovative Contact-Based Education workshops on anti-stigma and recovery principles, co-lead by academic/clinical trainers and a person with lived experience of MISUI; and (5) Recovery-Based Arts, a multi-week arts workshop for PHC providers and users to produce artwork related to MISUI and recovery, culminating in an exhibition to showcase artwork for the CESFAM providers, users, and community. The expected intervention outcomes are the following: Participation in the experimental group will result in a significant decrease in stigmatizing attitudes among PHC providers toward individuals with MISUI compared with the control group as measured by the Chilean version of the Opening Minds Scale for Health Care Providers Scale (OMS-HC); Participation in the experimental group will result in a significant decrease of PHC users experiences of stigma conveyed by PHC providers compared with the control group as measured by the Internalized Stigma of Mental Illness (ISMI) scale, validated for the Chilean population. The changes in attitudes and behaviors within the experimental group will be sustained over time as measured at 6 months-follow-up. To evaluate the effectiveness of this 18-month intervention, a 4-year, two-arm, cluster-randomized controlled trial is proposed, with CESFAMs being the unit of randomization (or “cluster”). Implementation Science approach will be taken to measure relevant implementation outcomes for each component of the intervention, and through qualitative data collection with CESFAM providers and authorities. Data analysis will be carried out using SAS 9.4 (specifically, using POC MIXED and PROC GENMOD) and R 3.5. Mixed-effect modeling will used for both PHC provider and user data, which will include individuals and CESFAMs as random effects and group (intervention/control) as fixed effects.DiscussionThis study represents a new stage of relevant and innovative research in mental health and stigma in Chile that will contribute to improving access and quality of care for people with MISUI. Evaluating the impact of the intervention model and its implementation will provide the necessary tools to scale the intervention up to other CESFAMs across Chile.Clinical trial registration[www.ClinicalTrials.gov], identifier [NCT05578066].