A study of emergency department visits in Nova Scotia has found no increase in suicide presentations among cannabis users following Canada’s legalisation of recreational cannabis in 2018, despite rising consumption during the COVID-19 pandemic.
The comprehensive study examined patients who presented to Nova Scotia’s emergency departments with both cannabis use and suicidal ideation, comparing presentation patterns between the immediate post-legalisation period and two years later.
The study, published in the journal BJ Psych Open, examined patient data from four main hospitals in Nova Scotia across two six-month periods: October 2018 to April 2019, and October 2020 to April 2021. During these periods, 43,957 unique patient encounters for cannabis-related problems were recorded.
From a subset of 2,184 patients across both time periods, they identified 271 patients whose chief complaint was related to suicidal ideation, representing 13.7% of the sample.
After comparing the data from both time periods, they found no significant difference in the number of presentations to emergency rooms by patients who had used cannabis and stated suicidal ideation as their primary complaint.
“The only difference we observed between the two time periods was for the number of follow-up visits post-index, with the earlier cohort having more presentations to the emergency department from the period directly following legalisation than a similar time period 2 years later,” the study authors said.
The study’s approach is based on established research showing that suicidal ideation can be as predictive of future suicide as actual suicide attempts. As noted in a systematic review cited by the researchers, “suicidal ideation may be just as likely as suicidal behaviour in predicting later suicide,” making emergency department presentations for suicidal thoughts a meaningful indicator of suicide risk in the population.
Research into the role of cannabis in suicidal behaviour is mixed, presenting contradictory results.
A 2019 study investigating toxicology reports found cannabis to be present in the blood of 30% of those who died by suicide. This study also linked an increase in fatal vehicle collisions to adult-use cannabis legalisation. Yet a 2024 study, published in the journal Archives of Suicide Research, found that medicinal cannabis could help lower suicidal thoughts by over 25% after three months.
Researchers acknowledged the complexity of studying suicide causation but concluded that whilst an association exists between suicidal ideation and cannabis use, cannabis is not necessarily a significant causal factor in suicide.
“In conclusion, individuals present to the emergency department with cannabis use less frequently than alcohol and, because of the often chronic nature of cannabis use in conjunction with patient presentation, cannabis use is not necessarily flagged as a concern,” the researchers stated. “However, it is clear from our work that suicidal ideation is associated with cannabis in emergency department presentations, and further work remains to determine the frequency and causality links in acute versus regular chronic use.”
