A Retrospective Cohort Study of Hospitalised Patients With First-Episode Substance-Induced Psychosis and First-Episode Psychosis: Comparing Long-Acting Injectable Antipsychotic Use and Post-Discharge Outcomes.

INTRODUCTION: Clinicians may not recommend long-acting injectable antipsychotics (LAI-APs) for patients diagnosed with first-episode substance-induced psychosis (FESIP), despite the risk of transition from FESIP to schizophrenia and the effectiveness of LAI-AP in early psychosis. We compared LAI-AP use and post-discharge outcomes between patients with first-episode psychosis (FEP) and those with FESIP during their index psychiatric hospitalisation. METHODS: We conducted a retrospective cohort study using electronic health record data from patients aged 18-39 who were discharged from inpatient psychiatry units at a public academic hospital between 2021 and 2024. Outcomes included administration of any LAI-AP during the index hospitalisation, documented recommendation of any LAI-AP, psychiatric rehospitalisation and emergency department (ED) encounters after discharge. RESULTS: The cohort included 90 patients with FEP and 84 patients with FESIP. Only one (1.2%) patient with FESIP received an LAI-AP compared with 10 (11.1%) with FEP (OR = 0.10, 95% CI = 0.002-0.71); LAI-AP was recommended to one (1.2%) patient with FESIP compared with 30 (33.3%) with FEP (OR = 0.02, 95% CI = 0.0006-0.16). Rehospitalisation occurred in 41 (45.6%) patients with FEP and 38 (45.2%) with FESIP; post-discharge ED encounters occurred in 50 (55.6%) and 52 (61.9%) patients, respectively. Time to first rehospitalisation and ED encounter after discharge did not differ between the groups. CONCLUSIONS: Despite similar post-discharge outcomes between patients with FEP and FESIP, administration or recommendation of an LAI-AP was rarer among those with FESIP. Our findings highlight uncertainty in treatment decision-making and support further research to guide early intervention strategies in patients with substance-induced psychosis.