Cannabis Use Medical Problems: Cannabis Use Disorder

"I think broadly there is a lot of interest for people around the world in what the Canadian experience is." "In a way, much of the cannabis policy decisions made internationally are going to come from Canadian data and U.S. data."

"We found that there have been concerning increases over time in the percentage of people with a new schizophrenia diagnosis who had received care for a cannabis use disorder before their diagnosis."

"I think the concern is that daily cannabis use has really increased in the last 15 years and at the same time the potency of cannabis has rapidly risen. Both are what prior literature says are major risk factors for psychosis and schizophrenia."

Dr. Daniel Myran, Canada Research Chair in Social Accountability, University of Ottawa 

Cannabis is now widely available since being legalized in October 2018. (Heather Waldron/CBC )

 

Ottawa researcher Dr. Daniel Myran led two new studies, both published in the journal JAMA Network Open this week, establishing a link between higher rates of death, along with 'concerning increases' in new schizophrenia diagnoses and cannabis use disorder. Cases of schizophrenia associated with cannabis use disorder, according to one of the studies, tripled between 2006 and 2022, when people looking for hospital treatment for cannabis use disorder increased by 270 percent.

 

People treated at  hospitals for cannabis use disorder, according to the second study, were at a significantly higher risk of death in comparison to the general population. Both studies were based on Ontario data in a period including cannabis legalization. Canada has some of the most reliable research data, given its history as the second country to legalize cannabis in 2018, and the only country to date to have built a retail market. The research work being produced on the impact of cannabis use disorder has caught international attention.

 

Links between cannabis use disorder and schizophrenia, along with psychosis, represent one focus of the research. The recent study found cannabis use disorder contributing to new cases of schizophrenia had tripled over the past 17 years in Ontario.  Individuals unable to deter themselves from cannabis use despite knowing it can cause serious social and health problems are defined by the term 'Cannabis use disorder'. Such situations are not in the majority; many people use cannabis without suffering such consequences.

 

A sharp increase in cases of psychotic disorders "not otherwise specified" (no previous diagnosis with a specific disorder) associated with cannabis use disorder was also noted in the study. A strong association between cannabis use disorder and schizophrenia in young males surfaced in the research with an estimated 18.9 percent of incidents of schizophrenia cases associated with cannabis use disorder in young males. In young women, also, cases of diagnosed schizophrenia had increased, while decreasing among older adults. 

 

Researchers from ICES, The Ottawa Hospital, University of Ottawa Department of Family Medicine and Bruyere Health Research Institute participated in the study which focused on all Ontario residents age 14 to 65 , eligible for universal health care in the years 2005 to 2022. Three policy time periods were encompassed; prior to legalization, following liberalization of medical cannabis, and finally after legalization of non-medical cannabis when a total of 118,650  individuals sought emergency department aid or hospitalization during that period, for cannabis use disorder. 

 

Nine percent of people with cannabis use disorder developed schizophrenia over the study period, in comparison to 0.6 percent of the general population. The second paper found a significantly higher risk of death among people who had been treated at hospital for cannabis use disorder, including all individuals between the ages of 15 and 105 living in Ontario between 2006 and 2021. 

HealthDay

"Our study highlights the growing public health challenge posed by the combination of increasingly high-potency cannabis and rising regular cannabis use."

" Although our study cannot establish causality, individuals with a hospital-based diagnosis of cannabis use disorder were at elevated risk of death."

"Although cannabis use disorder may not be directly responsible, our findings highlight a growing segment of the population at elevated risk of death and [who] may benefit from preventative measures."

Dr. Daniel Myran, scientist/investigator with ICES, Bruyere Health Research Institute, and associate scientist, The Ottawa Hospital