Background: While protocol-based psychological treatments have significantly advanced mental health care, real-world accessibility remains a challenge. Primary care, the main provider of mental health services, faces barriers such as limited resources and a diverse patient population with varying needs, making it difficult to rely solely on time-intensive, protocolized treatments. The Primary Care Behavioral Health (PCBH) model promotes brief, flexible interventions that may better accommodate these needs. However, limited research on these interventions raises concerns about potential undertreatment. To align with Universal Health Coverage principles, it is essential to identify which patient groups benefit most from resource-efficient protocol-based versus brief, flexible, and individualized treatments. Our main aim is to evaluate whether a integrating guided self-help into PCBH improves outcomes compared to the core PCBH model, as well as to assess whether patients identified as suitable for protocol-based interventions benefit more from the combined model.

Methods: Patients seeking help for mental or behavioral health problems at PCBH primary care centers will be randomized to one of two arms: core PCBH, where patients receive a contextual assessment and brief interventions tailored to their needs, or an extended PCBH model, where a diagnostic assessment determines whether patients receive brief interventions or guided self-help. The primary outcome is functional impairment, assessed at baseline and followed up at 4, 8, and 12 weeks (primary endpoint), as well as at 1 year. Secondary outcomes include symptom change, cost-effectiveness, and care process factors.

Discussion: The study design allows for comparisons of patient outcomes between the two care models, with a primary focus on evaluating superiority and a secondary focus on non-inferiority, cost-effectiveness, and care process factors. Overall, the project seeks to advance understanding of effective mental health interventions in primary care settings and inform decision-making regarding treatment approaches.