Can Marijuana Use Cause Anxiety Disorders?

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With marijuana legalization becoming common across the United States, mental health professionals have legitimate concerns about the impact the legalization movement might have on mental health at the population level. Previous research shows correlations between marijuana use, schizophrenia, and bipolar disorder, as well as correlations between marijuana use and depression. One recent study explores the potential connection between marijuana use and anxiety disorders: we’ll examine the results of that study in this article.

Marijuana: A Trend Toward Legalization

The debate around marijuana legalization in the United States is clearly tipping in one direction: toward full legalization. While some states may never legalize marijuana for recreational use, based on their cautious history with regards to marijuana and general resistance to the idea, it’s likely that before long, all states will legalize medicinal marijuana use, and most will legalize recreational use.

Here’s a quick timeline of the marijuana legalization/decriminalization movement:

1970s: Marijuana decriminalized in 14 states
1990s: Medical marijuana legalized in 21 states
2012-2022: Colorado and Washington legalize recreational marijuana use in 2012, and many states follow.
2024: Medical marijuana is legal in 38 states, while recreational marijuana use is legal in 24 states.

This data indicates As of February 1^st, 2024, 24 states and Washington, D.C. have legalized recreational marijuana for people over 21, and 38 states and Washington, D.C. have legalized medical marijuana. This means that for a majority of people in the U.S. – the legalized states make up more of our population than non-legalized states – marijuana is legal and available for purchase and use at any time.

That’s why research on the connection between marijuana and mental health is essential. As marijuana becomes more easily available, and rates of recreational use increase, it’s important to know the real facts about any potential negative consequences.

Marijuana Use and Anxiety: The New Study

The study that examines the connection between marijuana use and anxiety – “Development of an Anxiety Disorder Following an Emergency Department Visit Due to Cannabis Use: A Population-Based Cohort Study” – is the largest research effort ever conducted on the relationship of marijuana and mental health disorders.

Here’s the way the research team characterize their work:

“In this study we estimated the risk of having an incident healthcare visit for an anxiety disorder following an emergency department (ED) visit for cannabis use and explored factors associated with increased risk.”

The research objective, as we mention above, is critical as we move into a new era of marijuana legalization in the U.S. What gives this study weight is the sample size and length of the period in question. The research team examined records from 12.1 million people ages of 10 and 105 between January 2008 and March 2019. Over ten million people in a study period of over ten years is novel in mental health research. With a duration this long and a sample size this large, researchers can use statistical analysis to make accurate population-level estimates, which is exactly what we need with regards to marijuana use and mental health.

Before we examine the results of the study, let’s look at two things. First, the current rates of marijuana use in the U.S. Second, what research tells us about the consequences of marijuana use.

Marijuana Use in the U.S.: Facts and Figures

According to the 2022 National Survey on Drug Use and Health (2022 NSDUH), both past year and past month marijuana use increased between 2021 and 2022. This increase is part of a longer-term increase in recreational marijuana use that began around 2006. The increases we now observe follow observed decreases from 1979-1992, increases from 1992-2001, then decreases between 2001 and 2006. For an in-depth look at these trends, please read the 2020 study “Marijuana Legalization And Historical Trends In Marijuana Use Among US Residents Aged 12–25: Results From The 1979–2016 National Survey On Drug Use And Health.”

Now let’s look at the data from the 2022 NSDUH.

Marijuana Use: 2021 and 2022, Past Year and Past Month Use

Past Year:

2021:

12+: 19% (5.3 million)
12-17: 10.9% (2.8 million)
18+: 19.8% (5.0 million)

2022:

12+: 22% (6.1million)
12-17: 11.5% (2.9 million)
18+: 23% (5.9 million)

Past Month:

2021:

12+: 13.2% (3.7 million)
12-17: 6.1% (1.6 million)
18+: 13.9% (3.5 million)

2022:

12+: 15% (4.2 million)
12-17: 6.4% (1.6 million)
18+: 15.9% (4.1 million)

The data are clear: marijuana use is increasing as the number of states that legalize recreational marijuana use increases. That’s why we need to know more about the possible consequences of recreational marijuana use.

Marijuana Use: Physical, Psychological, and Emotional Consequences

A study conducted in 2014 by Dr. Nora Volkow, Director of the National Institute on Drug Abuse (NIDA) at the National Institutes of Health called Adverse Health Effects of Marijuana Use identified the consequences of long-term marijuana use on the human mind.

Here’s what Dr. Volkow and her team found:

Consequences Of Long-Term or Heavy Marijuana Use

Addiction
Impaired connections between brain cells (neurons)
Reduced self-awareness
Reduced alertness
Deficits in learning and memory
Deficits in executive function
Increased impulsivity
Problems with complex decision-making
Attenuated academic achievement
Cognitive disruption
Reduced IQ
Increased likelihood psychosis among people at elevated risk for schizophrenia or psychotic disorders

That list doesn’t include the negative physical consequences of marijuana use on the body. Research shows chronic marijuana use is associated with:

Chronic bronchitis
Increased risk of respiratory disease
Increased risk of heart attack in first hour after use
Cannabinoid Hyperemesis Syndrome (CHS: severe vomiting, nausea, dehydration after use)

While CHS is rare, the other consequences listed above are common, especially among people who regularly use marijuana over a long period of time. In addition, early onset of use increases risk of all the negative consequences listed above.

Next, let’s circle back to the study on marijuana and anxiety, in order to learn whether increased risk of an anxiety disorder belongs on our lists of potential negative consequences of marijuana use.

Marijuana Use and Anxiety: The Results

To recap, the study examined the records of over 12 million people over an 11-year-period. The goal of study was to understand the connection – if one exists – between an emergency department (ED) visit related to cannabis use and subsequent visits/diagnosis with an anxiety disorder. They types of anxiety disorder they included were generalized anxiety disorder, panic disorder, phobias, and anxiety disorders (not specified).

Let’s look at what they found.

Primary Analysis: ED Visit or Hospitalization for Anxiety Disorder

Among 12.1 million patients who visited the ED with no baseline anxiety disorder, 34,822 visited for marijuana related reasons. Among those:

2,429 developed anxiety or visited the ED for anxiety within a year (6.9%)
- Compared to 49,577 from the remaining 12,064,322 (0.41%)
4,294 developed anxiety or visited the ED for anxiety within three years (12.3%)
- Compared to 143,345 from the remaining 12,064,322 (1.19%)
5,450 developed anxiety or visited the ED for anxiety within five years (15.65%)
- Compared to 214,655 from the remaining 12,064,322 (1.78%)

Secondary Analysis: ED Visit or Hospitalization for Anxiety Disorder Among Patients With No Previous Mental Health or Substance Use Disorder (SUD)

Among 8.8 million patients who visited the ED with no mental health or substance use disorder at baseline, 12,587 visited for marijuana related reasons. Among those:

569 developed anxiety or visited the ED for anxiety within a year (4.5%)
- Compared to 20,354 from the remaining 8.8 million (0.23%)
966 developed anxiety or visited the ED for anxiety within three years (7.67%)
- Compared to 64,351 from the remaining 8.8 million (0.73%)
1,240 developed anxiety or visited the ED for anxiety within five years (9.85%)
- Compared to 101,317 from the remaining 8.8 million (1.14%)

For the primary analysis, a visit to the emergency room for cannabis-related reasons was associated with a hazard ratio of 3.69, or a risk of a subsequent ED visit for anxiety or diagnosis of anxiety disorder 3.7 times greater than the risk for people with an ED visit unrelated to marijuana. In addition, researchers found that the risk of any type of subsequent visit for anxiety – including an outpatient visit – was 3.9 times greater for people whose initial ED visit was unrelated to marijuana.

For the secondary analysis, a visit to the emergency room for cannabis-related reasons was associated with a hazard ratio of 9.37, or a risk of a subsequent ED visit for anxiety or diagnosis of anxiety disorder 9.3 times greater than the risk for people with an ED visit unrelated to marijuana.

What These Results Mean For Treatment and Prevention

These results are instructive.

First, we learned that an ED visit for marijuana is associated with a significantly increased risk of subsequent diagnosis of anxiety disorder and/or subsequent ED visit for anxiety. Second, we learned that among people with no prior mental health or substance use disorder (SUD) diagnosis, the associated risk is greater: a marijuana-related ED visit is associated with a greater risk of subsequent diagnosis of anxiety disorder and/or subsequent ED visit for anxiety. While this result appears counterintuitive, the research team explains that this likely includes patients with a pre-existing but undiagnosed anxiety disorder.

We can use this information in at least two ways. For emergency room personnel, it’s now essential to refer a person who presents with marijuana related problems to a mental health professional for a full psychiatric screening, with a focus on screening for anxiety. For treatment professionals who specialize in supporting patients with substance use disorder (SUD), it’s now essential to screen the subset of patients with cannabis use disorder for the presence of anxiety disorders.

With this new information, mental health professionals can triangulate the presence of cannabis use, history of ED visits for cannabis, and screening for anxiety disorders in order to tailor treatment to meet present needs and address the increased risk of subsequent mental health disorders such as anxiety. In other words, this study tells us that when a patient visits the emergency room for marijuana-related reasons, it’s now incumbent upon us to dig deeper, screen further, and offer support patients may not know they need.