Cannabis users had a 22% increased risk of an emergency department (ED) visit or hospitalization compared to nonusers, as determined from data from more than 30,000 individuals.
Although cannabis contains compounds similar to tobacco, “data published on the association between cannabis smoking and airways health have been contradictory,” and whether smoking cannabis increases a user’s risk of developing acute respiratory illness remains unclear, write Nicholas Vozoris, MD, of the University of Toronto, Canada, and colleagues.
In a study published in BMJ Open Respiratory Research, the investigators reviewed national health records data from 35,114 individuals aged 12 to 65 years for the period January 2009 to December 2015. Of these persons, 4807 of the 6425 who reported cannabis use in the past year were matched with 10,395 never-users who served as controls. The mean age of the study population at the index date was approximately 35 years, and 42% were women; demographics were similar between users and control persons.
Overall, the odds of respiratory-related emergency department visits or hospitalizations were not significantly different between the cannabis users and the control persons (3.6% vs 3.9%; odds ratio, 0.91). However, cannabis users had significantly greater odds of all-cause ED visits or hospitalizations (30.0% vs 26.0%; OR, 1.22). All-cause mortality was 0.2% for both groups.
Respiratory-related problems were the second-highest reason for all-cause visits, the researchers note. The lack of a difference in respiratory-related visits between cannabis users and nonusers conflicts somewhat with previous studies on this topic, which were limited, the researchers note in their discussion.
The negative results also might stem from factors for which the researchers could not adjust, including insufficient cannabis smoke exposure among users in the study population, noninhalational cannabis use, which is less likely to have a respiratory effect, and possible secondhand exposure among control persons.
“It is also possible that our analysis might have been insufficiently powered to detect a significant signal with respect to the primary outcome,” they note.
However, after controlling for multiple variables, the risk of an equally important morbidity outcome, all-cause ED visits or hospitalizations, was significantly greater among cannabis users than among control individuals, and respiratory-related reasons were the second most common cause for ED visits and hospitalizations in the all-cause outcome, they emphasize.
The study findings were limited by several factors, including the retrospective and observational design and the inability to control for all confounding variables, the researchers note. Other limitations include the use of self-reports and potential for bias, the inability to perform dose-response analysis, and the high number of infrequent cannabis users in the study population.
However, the results suggest that cannabis use is associated with an increased risk of serious health events and should be discouraged, although more research is needed to confirm the current study findings, they conclude.
Consider Range of Causes for Cannabis Emergency Visits
“With growing numbers or states legalizing recreational use of cannabis, it’s important to understand whether cannabis use is associated with increased emergency department visits,” Robert D. Glatter, MD, an emergency medicine physician at Lenox Hill Hospital, New York, told Medscape.
Previous studies have shown an association between increased ED visits and cannabis use in states, especially with edibles, where cannabis is legal, and “the current study reinforces the elevated risk of ED visits along with hospitalizations,” he said.
“While the researchers found no increased risk of respiratory-related complaints among users compared to the general population, there was an associated increase in ED visits and hospitalizations, which is important to understand,” said Glatter, who was not involved in the study.
“While this observational study found that the incidence of respiratory complaints was not significantly different among frequent users of cannabis, the increased odds that cannabis users would require evaluation in the emergency room or even hospitalization was still apparent even after the investigators controlled for such factors as use of alcohol, tobacco, illicit drug use, or other mental health–related disorders,” Glatter noted.
“That said, it’s a bit surprising that with the continued popularity of vaping, especially among teens, there was still not any appreciable or significant increase in respiratory complaints observed. Beyond this finding, I was not surprised by the overall conclusions of the current study, as we continue to see an elevated number of patients presenting to the ED with adverse events related to cannabis use.”
Glatter noted that “the majority of patients we see in the ED are associated with use of edibles, since it takes longer for the person to feel the effects, leading the user to consume more of the product up front, with delayed effects lasting up to 12 hours. This is what gets people into trouble and leads to toxicity of cannabis, or ‘overdoses,’ ” he explained.
When consuming edible cannabis products, “[p]eople need to begin at low dosages and not take additional gummies up front, since it can take up to 2 or even 3 hours in some cases to feel the initial effects. With the drug’s effects lasting up to 12 hours, it’s especially important to avoid operating any motor vehicles, bicycles, or scooters, since reaction time is impaired, as well as overall judgment, balance, and fine motor skills,” Glatter said.
Cannabis can land users in the ED for a range of reasons, said Glatter. “According to the study, 15% of the emergency room visits and hospitalizations were due to acute trauma, 14% due to respiratory issues, and 13% to gastrointestinal illnesses. These effects were seen in first-time users but not those with chronic use, according to the study inclusion criteria.”
Cannabis use could result in physical injuries through “impaired judgment, coordination, combined with an altered state of consciousness or generalized drowsiness, that could contribute to an increase in motor vehicle collisions, along with an increased risk for falls leading to lacerations, fractures, contusions, or bruising,” said Glatter. “Cannabis may also lead to an altered sense of perception related to interactions with others, resulting in feelings of anxiety or restlessness culminating in physical altercations and other injuries.”
The current study indicates the need for understanding the potential physical and psychological effects of cannabis use, Glatter said.
“Additional research is needed to better understand the relative percentage cases related to edibles vs inhalation presenting to the ED,” he noted. “There is no question that edibles continue to present significant dangers for those who don’t read labels or remain poorly informed regarding their dosing as a result of delayed onset and longer duration,” he said. To help reduce risk of toxicity, the concept of a “high lasting 12–15 hours, as with edibles, as opposed to 3–4 hours from inhalation must be clearly stated on packaging and better communicated with users, as the toxicity with edibles is more often from lack of prior knowledge about onset of effects related to dosing.”
In addition, “The potential for psychosis to develop with more chronic cannabis use, along with cannabinoid hyperemesis syndrome should be on every clinician’s radar,” Glatter emphasized.
“The bottom line is that as more states legalize the use of cannabis, it’s vital to also implement comprehensive public education efforts to provide users with the reported risks associated with not only inhalation (vaping or flower) but also edibles, which account for an increasingly greater percentage of ED visits and associated adverse effects,” he said.
The study was supported by the Lung Association–Ontario, as well as by grants from the Ontario Ministry of Health and the Ministry of Long-Term Care. The researchers and Glatter have disclosed no relevant financial relationships.
BMJ Open Respir Res. 2022 May;9:e001216. Full text
Heidi Splete is a freelance medical journalist with 20 years of experience.
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