Initiation of Antipsychotics During the First Year After First-Episode Psychosis: A Population-Based Study.

Background: Antipsychotics are recommended after first-episode psychosis. Knowledge on the current use patterns in real-world settings is thus important to inform clinical practice. We aimed to describe antipsychotic initiation during 1 year after first-episode psychosis and its associated factors.

Methods: Population-based cohort study using linked nationwide health and population registers from Norway. The study population comprised 8052 persons aged 16-45 years with first-episode psychosis diagnosed in secondary care (ICD-10 F20, F22-F29) in the period 2011-2019. Initiation of antipsychotic use was defined as being dispensed antipsychotics (ATC N05A, excl. lithium) at least once from -90 to +365 days from secondary care diagnosis of first-episode psychosis. Antipsychotic polypharmacy during follow-up was defined as having at least 90 days with overlapping drug use periods modeled using the Prescriptions to Drug Use Periods method. Adjusted risk ratios (aRRs) with 95% confidence intervals (CIs) for the association between socioeconomic and clinical factors and initiation of antipsychotic use were calculated using modified Poisson regression.

Results: In total, 4413 persons (54.8%) initiated antipsychotic use after first-episode psychosis with proportions ranging from 45.5% in 2012 to 62.1% in 2019. Oral formulations of olanzapine (34.9%), quetiapine (21.2%), and aripiprazole (11.6%) were most common at initiation, whereas long-acting injectables (LAIs) and clozapine were rarely used. Among the initiators, 13.8% started a polypharmacy period lasting more than 90 days. Factors associated with antipsychotic initiation were lower age (aRR 1.14, 95% CI 1.08-1.21; 26-35 years vs. 36-45 years), higher education (1.11, 1.05-1.18), being employed (1.04, 1.00-1.09), being hospitalized (1.13, 1.09-1.18), being diagnosed late in the study period (1.16, 1.11-1.22; 2017-2019 vs. 2011-2013), or with previously diagnosed bipolar disorder, depression, or anxiety disorders.

Conclusions: The antipsychotic use pattern is largely within the current clinical guideline. Primary non-compliance and disease severity may explain the socioeconomic and clinical differences related to initiation of antipsychotic use.