Frequency and patterns of substance-induced psychosis in persons with concurrent mental health and substance use disorders during the COVID-19 pandemic: A Norwegian register-based cohort study.

Background: Substance use may be associated with the onset of psychotic symptoms, necessitating treatment for individuals with comorbid mental health and substance use disorders (MHD/SUD). COVID-19 significantly impacted individuals with MHD/SUD, reducing access to appropriate care and treatment. Changes in drug availability and prices during the pandemic may have influenced drug consumption. This study aimed to determine the frequency of substance-induced psychosis (SIP) during COVID-19 among individuals with MHD/SUD and to explore substance fidelity by following patterns of SIP over time.

Method: In this retrospective cohort study, we analyzed data from all individuals with MHD/SUD registered in 2019-2021 in the Norwegian Patient Register. We used graphical approaches, descriptives, and Poisson regression to study occurrence and risk of SIP episodes in the three-year observation period. Sankey diagrams were used to examine trajectories of psychotic episodes induced by various substances.

Results: Despite a decrease in individuals diagnosed with SIP during COVID-19, SIP episodes increased overall. We observed a decline in cannabis-induced psychosis, but a rise in SIP episodes involving amphetamines and multiple substances. Among individuals with recurrent SIP episodes, the psychosis was more often induced by different substances during COVID-19 (2020: RR, 1.50 [95% CI, 1.34-1.67]; 2021: RR, 1.30 [95% CI, 1.16-1.46]) than in 2019.

Conclusion: During COVID-19, fewer individuals were hospitalized with SIP, but those patients experienced more episodes. There were fewer cannabis-induced psychotic episodes, but more SIP hospitalizations caused by central stimulants and more SIP diagnoses caused by different substances, possibly reflecting changes in drug availability and pricing.