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There is debate in the medical community over the relationship between cannabis and anxiety disorder. PATRICK T. FALLON/Getty Images
  • Researchers report that emergency room visits for cannabis may be linked to anxiety diagnoses.
  • They say that men and younger people who used cannabis may be at higher risk for anxiety.
  • There continues to be debate over whether cannabis causes anxiety or can be used to remedy the condition.

A new study says cannabis may not be so relaxing for everyone.

Researchers report that 27% of people who went to an emergency department for cannabis use developed a new anxiety disorder within three years.

The research team from Canada said their research published in the journal eClinical Medicine is the largest study examining the relationship between anxiety and cannabis use.

The researchers looked at more than 12 million people living in Ontario, Canada, between 2008 and 2019, none of whom had ever received treatment or a diagnosis for anxiety.

The team examined the health record data, comparing the risk of developing an anxiety disorder for those who went to an emergency for cannabis use compared to the general population.

“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,” said Dr. Daniel Myran, the lead study author and a Canada Research Chair in social accountability at the University of Ottawa, an International Cultural Exchange Services adjunct scientist, an investigator at the Bruyère Research Institute, and a clinician investigator at The Ottawa Hospital, in a statement.

Researchers said they found that 27% of the individuals who went to an emergency department for cannabis use were diagnosed with a new anxiety disorder within three years, compared to 5% of the general population — a nearly 4-fold increase after accounting for social factors and other mental health diagnoses.

They said of those already diagnosed 12% of people who went to an emergency room for cannabis use were hospitalized or visited an emergency room again for an anxiety disorder within three years, compared to 1% of the general population — another nearly 4-fold increased risk after accounting for other mental health diagnosis and social factors.

In people who visited an emergency room with cannabis as the main reason, the risk of hospitalization or another emergency visit for an anxiety disorder increased by more than 9 fold compared to the general population.

The researchers also reported that women and men and individuals of all ages going to an emergency room for cannabis use were at elevated risk of developing new anxiety disorders relative to the general population, with men and younger adults (10 to 24 years) at particularly elevated risk.

The scientists acknowledged there’s an ongoing debate about whether cannabis actually causes people to develop anxiety or if their cannabis use reflects a condition already there for which they’re medicating.

However, the researchers said their study indicated that cannabis may make anxiety worse. They also said it’s possible cannabis may delay other evidence-based treatments and may substantially worsen anxiety symptoms.

“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 said. “Our study cautions that in some individuals, heavy cannabis use may increase their risk of developing anxiety disorders.”

Daniele Piomelli, PhD, the director of the UC Irvine Center for the Study of Cannabis in California who wasn’t involved in the study, told Medical News Today that the effects of cannabis on people has never been a one-size-fits-all proposition.

“Cannabis can have both anti-anxiety and pro-anxiety effects, depending on dose, [and] experience with the drug,” Piomelli said. “We have known about these dual action for a long time. The anti-anxiety effect is rooted in the protective functions of the endocannabinoid system, which is exquisitely involved in coping with stress and curbing anxiety. But we still do not understand how cannabis can cause anxiety in vulnerable individuals.”

Piomelli added that cannabis is, generally, more powerful now.

For example, the THC potency in dried cannabis has increased from an average of 3% in the 1980s to about 15% today.

“One can even find cannabis products (oils, etc.) that contain more than 80% THC,” Piomelli said.

Ashley Murry, the chief clinical officer of Sana Lake Recovery Center in Missouri who wasn’t involved in the study, told Medical News Today the link between anxiety and cannabis is interesting and “requires a delicate approach.”

“Research in this field is varied and has shown benefits as well as drawbacks,” Murry said. “Most people today have used CBD, a compound found in cannabis. Research has shown that CBD can offer anti-anxiety properties and alleviate stress. Many individuals have reported that they feel calmer after consuming cannabis, although the effects vary depending on the type of product and the individual response.”

But adding THC, makes it a different product, Murry noted.

“On the other hand, THC acts as the psychoactive compound in cannabis and can, however, increase anxiety symptoms in individuals as THC can increase the heart rate and induce paranoia,” she said. “If your sole reason for using cannabis is to reduce or manage your anxiety levels, it might lead to dependence and those suffering from pre-existing anxiety disorders may be more susceptible to its adverse effects.”

“I would suggest that before you use cannabis for any reason, it is best to consult with a healthcare professional, especially for those individuals suffering from pre-existing conditions,” she said.

Dr. Sherry Yafai, an emergency medicine physician at Saint John’s Physician Partners Urgent Care and Adjunct Assistant Professor at Saint John’s Cancer Institute in California and cannabis specialist, said the study didn’t account for “glaring co-variates in the group, namely, consumption of other drugs and alcohol.”

“We are well aware that the use of and misuse of alcohol, stimulants and opiates – to name a few – can contribute to a variety of health consequences, including anxiety,” Yafai, who wasn’t involved in the study, told Medical News Today. “This article failed to remove these patients from the comparison, likely because they would not have been able to show any effects from cannabis use alone.”

Yafai also said the researchers “missed the fact that 19% of adults have anxiety disorders… with an estimated 31% of adults having an anxiety disorder at some point in their lives.”

Yafai added that anxiety is a common diagnosis to “miss” during an emergency room visit as doctors are usually trying to rule out life threatening issues in that setting. She said that invalidates using the “general population” as a means for comparison.

“It should have been a comparison to… statistics of global anxiety and not all-comers to the [emergency room], which more commonly are presenting for things like stroke, heart attacks, abdominal pain, vomiting and diarrhea, to name a few,” she said.

Yafai also said a formal diagnosis of anxiety requires symptoms for at least six months, meaning people attempting to self-medicate in the study would have been mislabeled.

“Perhaps what this article should be highlighting, is that a presentation to the [emergency department] with cannabis use, might give physicians an opportunity to intervene in a positive way, to help patients with developing anxiety to steer them to better treatment practices,” she said. “Having those discussions, may impact an individual’s life in a more meaningful way.”