TY - JOUR AU - A. O'Donnell AU - E. Kaner AU - B. Hanratty AU - E. Gilvarry AU - S. Wigham AU - K. Jackson A1 - AB - INTRODUCTION: There is an acknowledged care gap for patients with co-occurring substance use and mental ill-health. This study sought to use complexity theory to help make sense of the experiences of people who deliver or commission formal care for patients with alcohol use disorder and depression across one specific health and social care system. METHOD: Qualitative interviews with 26 health and social care professionals in the North East and North Cumbria Integrated Care System, England, were conducted. Data analysis was undertaken using reflexive thematic analysis and informed by key concepts from complexity theory. RESULTS: Three main themes were identified: (1) how the interplay between risk, stigma and resource pressures influences how care professionals interpret and apply practice guidelines; (2) how individualised and disjointed practices have structural and historical roots, in particular the impact of health service commissioning cycles; (3) ways in which practitioners have been able to adapt and engage in creative practice to temporarily plug gaps in care. CONCLUSIONS: The pressure of working with increasingly scarce resources, within a highly fragmented, shifting, and risk-averse care infrastructure, adversely affected professionals' capacity to provide consistent, patient-centered support. Innovations have emerged that address some of these barriers, but further investment is needed to better support the substance use and mental health workforce, including lived experience peer workers. AD - Population Health Sciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom.; Cumbria, Northumberland Tyne and Wear NHS Foundation Trust, St. Nicholas Hospital, Newcastle upon Tyne, Tyne and Wear, United Kingdom. AN - 41091787 BT - PLoS One C5 - Opioids & Substance Use CP - 10 DO - 10.1371/journal.pone.0334524 DP - NLM ET - 20251015 IS - 10 JF - PLoS One LA - eng N2 - INTRODUCTION: There is an acknowledged care gap for patients with co-occurring substance use and mental ill-health. This study sought to use complexity theory to help make sense of the experiences of people who deliver or commission formal care for patients with alcohol use disorder and depression across one specific health and social care system. METHOD: Qualitative interviews with 26 health and social care professionals in the North East and North Cumbria Integrated Care System, England, were conducted. Data analysis was undertaken using reflexive thematic analysis and informed by key concepts from complexity theory. RESULTS: Three main themes were identified: (1) how the interplay between risk, stigma and resource pressures influences how care professionals interpret and apply practice guidelines; (2) how individualised and disjointed practices have structural and historical roots, in particular the impact of health service commissioning cycles; (3) ways in which practitioners have been able to adapt and engage in creative practice to temporarily plug gaps in care. CONCLUSIONS: The pressure of working with increasingly scarce resources, within a highly fragmented, shifting, and risk-averse care infrastructure, adversely affected professionals' capacity to provide consistent, patient-centered support. Innovations have emerged that address some of these barriers, but further investment is needed to better support the substance use and mental health workforce, including lived experience peer workers. PY - 2025 SN - 1932-6203 SP - e0334524 ST - Care professionals' accounts of providing support and treatment for people with co-occurring alcohol use disorder and depression in the North East of England, UK: A qualitative study informed by complexity theory T1 - Care professionals' accounts of providing support and treatment for people with co-occurring alcohol use disorder and depression in the North East of England, UK: A qualitative study informed by complexity theory T2 - PLoS One TI - Care professionals' accounts of providing support and treatment for people with co-occurring alcohol use disorder and depression in the North East of England, UK: A qualitative study informed by complexity theory U1 - Opioids & Substance Use U3 - 10.1371/journal.pone.0334524 VL - 20 VO - 1932-6203 Y1 - 2025 ER -