Heavy Cannabis Use Linked to Increased Risk for Anxiety

Daniel Myran MD, MPH, CCFP, FRCPC

Credit: uOttawa

Many individuals who had an emergency department visit for cannabis use developed a new anxiety disorder within 3 years, according to a new study. This applied to 27.5% of individuals who visited the emergency room due to heavy cannabis use.¹

Although a debate remains about whether cannabis use causes individuals to develop anxiety disorders or if individuals with anxiety use cannabis to self-medicate, the study found cannabis use may worsen anxiety. The findings support another 2024 study finding cannabis is linked to worsened psychiatric symptoms.²

The population-based cohort study, led by Daniel T. Myran, MD, MPH, CCFP, FRCPC, from the Clinical Epidemiology Program at Ottawa Hospital Research Institute in Ontario, Canada, was the largest study evaluating the association between cannabis use and anxiety. The study included 12 million individuals living in Ontario, Canada between January 2008 – March 2019, aged 10 – 105 years, who had never received a diagnosis of anxiety.

In total, 34,833 (0.29%) had an incident emergency department visit due to cannabis. Additionally, the study had 19,460 (63.9%) individuals with an emergency department visit for cannabis use and 9,771,533 (81%) individuals in 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 disorder,” said Myran in a press release.³

The team used health record data from ICES to evaluate the risk of developing an anxiety disorder for individuals who had an emergency department visit for cannabis use.¹ Investigators obtained data age, sex, rural residence, neighborhood income quintile, health care use in the 3 years before the index, and mental health conditions. The primary outcome was the incident emergency department or hospitalization for an anxiety disorder.

For anxiety disorders, the team included panic disorders, phobic disorders, generalized anxiety disorders, and anxiety disorders not specified; they did not include anxiety disorders with organic causes, obsessive-compulsive disorders, adjustment disorders, or post-traumatic stress disorders.

Investigators found individuals with an emergency department visit for cannabis use were, compared to a general population, younger (mean age 27.6 vs. 44.9 years), more likely to be male (66.7% vs. 49.1%), reside in the lowest-income quintile neighborhood (28.8% vs. 19.3%), and likely to have had prior outpatient mental health visits (59.8% vs. 26%).

Data showed individuals with cannabis use who had an emergency department had a greater risk for anxiety, as 27.5% of individuals who had an emergency department for this reason were diagnosed with a new anxiety disorder within 3 years—the risk increased 3.9-fold after accounting for social factors and other mental health diagnoses (adjusted hazard ratio [aHR] 3.88 95% CI 3.77–3.99). In contrast, only 5.6% of the general population were diagnosed with a new anxiety disorder.

Moreover, 12.3% of individuals who had an emergency department visit for cannabis had a hospitalization or an emergency department visit for an anxiety disorder, but this only applied to 1.2% of the general population. The team observed a 3.7-fold increased risk after accounting for social factors and other mental health diagnoses (aHR, 3.69; 95% CI, 3.57 – 2.82).

Furthermore, a secondary analysis demonstrated 23.6% of individuals with an emergency department visit due to cannabis had their first outpatient visit, emergency department visit, or hospitalization for an anxiety disorder within 3 years compared to 5.6% of the general population (aHR, 3.88; 95% CI, 3.77 – 2.99).

For individuals who visited the emergency department for cannabis specifically, the risk of having a hospitalization or emergency department visit for an anxiety disorder increased by 9.4-fold compared to the general population. Additionally, younger people (10 – 24 years) and men were at an increased risk for developing new anxiety disorders (aHR, 5.67; 95% CI, 5.19 – 6.21). Women had a lower risk (aHR, 3.22; 95% CI, 2.95 – 3.52).

A limitation in the study, as investigators highlighted, is how the study focuses on care for cannabis use instead of cannabis itself. Therefore, individuals with cannabis use who do not receive care would technically be a part of the general population, which ultimately would create bias in the findings. The team also wrote how the study only captured severe initial presentations of anxiety, the data lacked information on patterns of cannabis use such as frequency of use, type, and potency of products, and some individuals may have already had anxiety but not yet been diagnosed due to the study design of excluding previous healthcare visits for anxiety disorders.

“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.³ “Our study cautions that in some individuals, heavy cannabis use may increase their risk of developing anxiety disorders.”

^References

1. ^{Myran, D, Harrison, L, Pugliese, M. Development Of An Anxiety Disorder Following An Emergency Department Visit Due To Cannabis Use: A Population-Based Cohort Study. The Lancet. 2024. https://doi.org/10.1016/j.eclinm.2024.102455}
2. ^{Heavy Cannabis Use Increases Risk of Developing an Anxiety Disorder, Study Suggests. EurekAlert! February 5, 2024. https://www.eurekalert.org/news-releases/1033432?. February 6, 2024.}
3. ^{Derman, C. Understanding the Link Between Substance Use and Psychiatric Symptoms, with Randi Schuster, PhD. HCPLive. January 31, 2024. https://www.hcplive.com/view/understanding-the-link-between-substance-use-and-psychiatric-symptoms-with-randi-schuster-phd. Accessed February 6, 2024.}