Implementing a complex psychosocial intervention for unstably housed Veterans: A realist-informed evaluation case...

Area of Science:

• Implementation Science
• Health Services Research
• Psychiatry

Background:

• Co-occurring mental health and substance use disorders (COD) affect many Veterans, yet few receive integrated care.
• The MISSION-Vet intervention was developed to address this gap by providing integrated psychosocial services.
• Understanding the factors influencing the successful implementation of such complex interventions is crucial for improving care delivery.

Purpose of the Study:

• To identify the generative mechanisms explaining the adoption, implementation, and fidelity of the MISSION-Vet intervention in Veterans with COD.
• To understand "how, for whom, and under what conditions" MISSION-Vet implementation is effective within a complex adaptive system.
• To explore the interplay of context, mechanisms, and outcomes in the implementation of a manualized psychosocial intervention.

Main Methods:

• A hybrid III trial was conducted across two VA healthcare systems (Sites A and B) to evaluate the implementation of MISSION-Vet.
• A two-site case study utilized 42 semi-structured interviews guided by the Consolidated Framework for Implementation Research (CFIR).
• Data were coded, and CFIR constructs were used to generate "Context + Mechanism = Outcome" configurations to analyze implementation dynamics.

Main Results:

• Site B demonstrated higher adoption, implementation, and fidelity compared to Site A.
• Adoption was influenced by external policy and "tension for change"; implementation intensity by "peer pressure" and "self-efficacy"; and fidelity by "staffing" and "facilitation."
• Specific contexts activated mechanisms differently, impacting the various stages of MISSION-Vet implementation.

Conclusions:

• The study delineated how specific contextual factors trigger mechanisms to drive different stages of implementing a multi-faceted COD treatment intervention.
• Findings underscore the dynamic and interdependent nature of implementation factors at individual, organizational, and system levels.
• This research contributes to a more precise understanding of causal relationships in complex intervention implementation, informing responsive implementation practices.