Scientists link hospitalisation for cannabis use to increased risk of anxiety disorders
An emergency visit to a hospital for marijuana use could increase a person’s risk of developing an anxiety disorder, a large new study has found.
The study published in The Lancet’s eClinical Medicine journal included more than 12 million individuals who lived in Ontario, Canada between 2008 and 2019 without an anxiety diagnosis or previous treatment.
Of those millions, researchers compared the more than 34,000 individuals who visited the accident and emergency department for cannabis use to the general population.
More than 27 per cent of those individuals treated for cannabis use developed an anxiety disorder within three years, they found, whereas, in the general population, just under 6 per cent of people developed a new anxiety disorder.
People who had visited an emergency department for heavy marijuana use thus had a 3.9-fold increased risk of developing a new anxiety disorder after accounting for other factors.
The researchers also found that more than 12 per cent of people who visited an emergency department for marijuana use were hospitalised or treated again for an anxiety disorder within three years compared to just 1.2 per cent of the general population.
This represented a 3.7-fold risk for people treated in hospital for heavy cannabis use.
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“Our results suggest that individuals requiring emergency department treatment for cannabis use were both at substantially increased risk of developing a new anxiety disorder and experiencing worsening symptoms for already existing anxiety disorders,” Dr Daniel Myran, lead author of the study from the University of Ottawa, said in a statement.
“Cannabis use has rapidly increased in Canada over the past 15 years and there is a general sense that cannabis is relatively harmless or has health benefits,” Myran added.
“Our study cautions that in some individuals, heavy cannabis use may increase their risk of developing anxiety disorders”.
While men and women of all ages who went to the emergency department for cannabis use had an increased risk of developing an anxiety disorder, younger adults between the ages of 10 and 24 and men were particularly at risk, the researchers said.
Study limitations
One of the limitations of the study is that it “captures care for cannabis use rather than cannabis use itself,” the authors said.
People with disordered marijuana use who were not hospitalised in an emergency setting would have been in the general
population, for instance. The data also lacked information on the frequency of use and potency of products.
The study still suggests that “individuals with cannabis use requiring treatment in the [emergency department] or hospital setting are at a high risk of anxiety disorders and may benefit from further assessment and intervention”.
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A separate US study published in April 2023 found that around 17 per cent of patients visiting the emergency room for acute cannabis toxicity had “a chief complaint of anxiety”.
A report from the University of Washington released in 2017, meanwhile, said one of the active ingredients in marijuana, THC, appeared to “decrease anxiety at lower doses and increase anxiety at higher doses”.
The Canadian researchers of the study released this week said their findings “have important clinical and policy implications given the increasing use of cannabis over time and trend towards legalisation of cannabis”.
Across most of Europe, cannabis remains illegal, but Germany moved closer to legalising the drug for recreational use last year.