Variation in Structural Characteristics Among 20 Medical Psychiatry Units in the United States: A Survey-Based Study

Background: Medical psychiatric units (MPUs) are specialized hospital units providing integrated care for patients with co-occurring medical and psychiatric illnesses. Despite their growing relevance, data on their structural characteristics in the United States remain sparse. This study aims to inventory and analyze the structural characteristics of 20 US MPUs, categorizing them using Kathol's and Van Schijndel's frameworks, and identifying shared components to inform future MPU design and quality standards. Methods: A structured telephone survey was conducted with 20 MPUs from 15 states. Units were categorized as medical attending MPUs, psychiatric attending MPUs, or co-attending MPUs, based on physician involvement. Characteristics assessed included medical and psychiatric acuity capabilities, staffing, physical design, and diagnostic services. Data were analyzed for shared and variable characteristics, and findings were compared with prior studies. Results: Most MPUs aligned with Kathol's Type III, characterized by medium to high medical and psychiatric acuity capabilities. Shared characteristics included integrated nursing practices, 24/7 diagnostic availability, and access to intensive care unit-level care. However, significant variation existed in location, staffing, and technical capabilities. Most units were psychiatry attending or co-attending MPUs. Conclusions: The US MPUs included primarily serve patients with medium to severe medical and psychiatric illnesses. Our findings highlight shared and variable features across MPUs, emphasizing the role of contextual needs and financial incentives in shaping their design. This study provides the most comprehensive inventory of US MPUs to date and proposes features to guide future MPU development and standardization.