Public Health Service Clinical Journeys of Patients With Primary Substance Use Disorders Who Are Subsequently Diagnosed With Non‐Affective Psychotic Disorders

INTRODUCTION: Psychosis is a debilitating condition and prompt treatment is a key prognostic factor. Early intervention services aim to provide timely care, but co-occurring substance use disorders (SUDs) complicate treatment, leading to poorer outcomes. This study examined the clinical journey of individuals with SUD who were subsequently diagnosed with a psychotic disorder, focusing on the interval between diagnoses to understand this issue. METHODS: Patient pathways were constructed using linked health data (2005-2022) from Western Australia for individuals aged ≥ 18 years with a diagnosis of SUD followed by a primary psychotic disorder. Service events across emergency departments (EDs), inpatient and community mental health services were analysed. Descriptive statistics and subgroup analyses examined variations based on the time between diagnoses, sex, remoteness and socioeconomic status. RESULTS: Analysis of 7568 patient pathways revealed a median diagnostic interval of 1.9 years. Initial SUD diagnoses occurred most frequently in inpatient settings (62%), whilst psychoses diagnoses were most common in EDs (46%). Common diagnostic pathways included inpatient to ED (28%) and inpatient to inpatient (24%). Subgroup analyses showed women had a 7-month longer diagnostic interval and six more mental health service events than men. Remoteness and socioeconomic disadvantage correlated with increased diagnosis in inpatient settings and decreased diagnosis in EDs. CONCLUSION: A significant delay between diagnoses is likely associated with poorer outcomes. Integrated service delivery, particularly between EDs and specialised mental health services, is important for early intervention. Patient demographics and geographic location influence diagnostic pathways, suggesting targeted interventions to improve access to prompt, appropriate care.