Introduction: Acute psychosis is a disruptive change in mental state that requires the mobilization of significant resources for its immediate treatment and ongoing management in the emergency department (ED). Cannabis-induced psychotic disorder (CIP) is one potential cause; however, the diagnosis may be overlooked due to limited understanding of the etiology of CIP. Methods: This study employed a retrospective cohort analysis of all CIP cases admitted from a tertiary care ED in Edmonton, Alberta between 10/2016 and 10/2018 – the month cannabis was legalized in Canada. Charts were identified based on a most responsible diagnosis of CIP, as defined by ICD-10 code F12.5. Two reviewers abstracted data using a standardized form, which was entered into a database; 10% of charts were analyzed by both reviewers to examine inter-rater reliability. Patients were excluded if there was any documentation of methamphetamine use within the week prior to presentation. Outcomes included management, symptom profile, and length of stay. Results: In total there were 44 cases of CIP identified in 40 unique patients during the two-year period. The largest age group of patients (n = 14, 35%) were between 15-20 years old and the median length of admission was 6 days. A minority of patients (n = 13, 32.5%) had a previous psychiatric diagnosis. A distinct clinical picture evolved during the summation of patient symptoms in the ED with 65% of patients (n = 26) exhibiting persecutory delusions and 52.5% endorsing auditory hallucinations (n = 21). Only four patients were found to have visual hallucinations, three of which also had auditory hallucinations. Most patients (n = 34, 85%) were treated with an antipsychotic medication in the ED and during their time as inpatients, but only 70% of patients were prescribed an antipsychotic medication at the time of discharge (n = 28). Conclusion: This study is the first of its kind describing a cohort of patients with CIP in a Canadian ED setting. The patients presenting to the ED who would later be diagnosed CIP were more likely to be 15-20 years old, experiencing persecutory delusions, and unlikely to be experiencing isolated visual hallucinations. With the recent legalization of cannabis in Canada, further prospective research is required to determine any changes in the characteristics, incidence, and prevalence of CIP, as well as data from other centers to look for any regional differences in the presentation and management of CIP.
