Avid cannabis smokers were more likely to suffer from anxiety disorders
Canadian researchers found that 27 percent of people who went to the emergency room for cannabis use developed a new anxiety disorder within three years. That's nearly four times the rate compared to the general population.
Cannabis is the third most commonly used drug after alcohol and nicotine. Its use is increasing worldwide, and especially significantly in countries like Canada since legalization. There is a perception that cannabis is relatively harmless or even healthy. However, a new study has provided further evidence to the contrary: heavy cannabinoid use increases the risk of developing anxiety disorders.
Marijuana use has already been linked to cognitive decline and the development of mental illnesses, primarily psychosis. Many studies have shown that cannabis and withdrawal in its absence can cause acute symptoms of anxiety. On the other hand, according to a meta-analysis, people suffering from anxiety and anxiety-related disorders are more likely to use cannabinoids.
However, most studies on cannabis use have had methodological problems and inconsistent results due to small samples of participants, large differences in rates of cannabis use, and differences in the very definition of anxiety. For example, anxiety symptoms and their severity were sometimes defined on the basis of self-report rather than a doctor's diagnosis. The relationship between cannabis use and the development of anxiety disorders was therefore not fully understood. A new study has expanded our understanding of their connection and is the largest on the subject to date.
The study, published in The Lancet, included more than 12 million people living in Ontario between 2008 and 2019. The authors used administrative data from ICES medical records to compare the risk of developing an anxiety disorder in people who went to the emergency department for cannabis use (there were 34,822 participants, 0.29 percent of all) compared to the general population.
As a result, the researchers came to several conclusions.
Cannabis smokers had a 3.9-fold increased risk of developing a new anxiety disorder compared to the general population after accounting for social factors and other mental health diagnoses. Within three years, 27.5 percent of those who sought medical attention for cannabis use were diagnosed with a new anxiety disorder - compared to 5.6 percent of the general population.
The risk of severe or worsening anxiety disorders increased 3.7 times after accounting for social factors and other mental health diagnoses. At three years, 12.3 percent of people who sought medical attention for cannabis use were hospitalized with an anxiety disorder, compared to 1.2 percent of the general population.
The results showed that people who required treatment in the emergency department for cannabis use were at increased risk of developing a new anxiety disorder and experiencing worsening symptoms of existing anxiety disorders. The final risk scores for these disorders after adjustment were more than three times higher than the risk in the general population. Young men under the age of 24 were particularly at increased risk.
The scientists admitted that their study could not isolate a causal relationship between cannabis use and the development of anxiety disorders. In addition, they noted other limitations of their work.
First, while the use of administrative health data has some advantages (large cohorts with reduced risk of selection bias), it reflects an individual's concern about cannabis use rather than use per se. Second, the data lack information on the nature of cannabis use (frequency of use, product type, and THC content).
Despite these points, the authors cautioned against using cannabis to treat anxiety symptoms, given the lack of evidence for its efficacy and that other evidence-based treatments may be delayed in this way.