Many people smoke cannabis to unwind, but it doesn’t always work that way.
The effects cannabis can have on mood varies widely, leaving some people calm and content and others anxious and irritable, research shows.
The effects of weed can even vary with each experience and may be influenced by how anxious you are when you ingest the drug. A person could smoke or ingest the same amount of cannabis on two different occasions and have two completely different experiences, said Ryan Vandrey, a professor of psychiatry and behavioral sciences at Johns Hopkins Medicine.
"A lot of it could be the baggage you're carrying into the situation," Vandrey said. "It's really hard to predict."
Why does cannabis affect people differently?
Experts say the type of cannabis, the amount taken and the way it's used - smoked, vaped or eaten, for example - all determine how it affects the body. Cannabis contains varying levels of different compounds. THC, or delta-9-tetrahydrocannabinol, is the component of cannabis responsible for weed's "floaty" high. CBD, or cannabidiol, appears to work through different receptors in the brain and doesn't result in the same high.
"We have this way of talking about cannabis as if it's one thing, and it isn't," said Staci Gruber, the director of the Marijuana Investigations for Neuroscientific Discovery program at McLean Hospital in Massachusetts. The plant is "unbelievably complex in the most amazing way."
The effect of cannabis also can vary by how you ingest it. When you smoke or use a vaporizer to inhale cannabis, the drug can metabolize in the body in "moments to minutes," Gruber said. It can take 45 minutes or more for someone to feel the effects of an edible, and the time will depend on what's already in your stomach.
And not everyone gets the same "high." Your age, how frequently you use cannabis, how sensitive you are to THC and how fast you're able to metabolize the drug all factor into how the drug affects you.
"We all differ dramatically," said Bryon Adinoff, a clinical professor of psychiatry at the University of Colorado School of Medicine and the president of the advocacy group Doctors for Cannabis Regulation. "There's all these things that are going to influence how we respond to cannabis."
How the level of THC affects anxiety
Cannabis has different effects at lower doses than high doses. Generally, low doses of THC are well-tolerated, stimulating a release of dopamine, and higher doses of THC can cause people to feel anxious, said Peter Grinspoon, a primary care physician at Massachusetts General Hospital and the author of "Seeing Through The Smoke," a book reviewing the latest medical research on cannabis.
"The main way you can get into mischief with cannabis is by using too high a dose and becoming very, very anxious," said Grinspoon, who's also an instructor at Harvard Medical School.
"There are some patients who can't use it at all, even a teeny bit, because any little bit makes them anxious."
Your state of mind matters
Cannabis affects virtually every neural connection in the brain, even more so than stimulants such as cocaine and opioids, said Judy Grisel, a professor of psychology at Bucknell University and the author of "Never Enough: The Neuroscience and Experience of Addiction." This, in turn, means cannabis can cause a wide array of reactions, depending on the person, she said.
"It's going to turn up the volume on everything," Grisel said, which is why food tastes better and music sounds better to some people when they're high.
Many people swear by the calming effect of weed, but Grisel said there doesn't seem to be a "molecular reason" why THC would alleviate someone's feelings of anxiety or stress. Instead, people may feel a calming or relaxing effect because the drug can enhance how you're already feeling.
If you're using cannabis on "a nice, sunny breezy day," Grisel said, then the weed is going to enhance the mellow, relaxing ambiance. This also means that for those who are feeling anxious, cannabis may make them more sensitive to stress or prone to paranoia.
"When you smoke, every synapse is reverberating, which means that everything is boosted," Grisel said. "The low-level, maybe sub-threshold, anxiety that you've been dealing with at work or school, or thinking about global climate change or whatever, that stuff is also enhanced."
Sariyah, a 20-year-old who lives in Georgia, used to smoke cannabis every day when she got off from work. She said she felt like the weed helped her unwind. But then, a few months ago, cannabis started making her feel worse.
"Eventually, over time, it started making my heart race," said Sariyah, who asked that her full name not be used because her family doesn't know she uses cannabis.
Sariyah said weed often enhances her "deepest thoughts." If she's sad or anxious, she feels more so when she smokes. Sariyah said she has cut back and wants to find the dose of weed that reliably works to soothe her anxiety.
Now, she smokes about twice a week. "A majority of the time, I'm not anxious when I smoke, but sometimes it's there," Sariyah said. "Sometimes it just comes out of nowhere."
Anxiety risk is higher for teens
Decades of clinical research has found THC can negatively effect the developing brain, and regular cannabis use in the teen years is associated with a higher likelihood of developing anxiety and depression later in life.
"Smoking early can catalyze anxiety and depression," Grisel said. "It's not exactly clear how that happens but the evidence for it is very strong."
Smoking cannabis regularly for a long period of time will change how your brain responds to the drug, experts say. Frequent and prolonged use may result in a decrease in the number of cannabinoid receptors, which is why people may begin to feel fewer effects of the drug over time.
Megan Mbengue, a nurse and cannabis educator who also sells her own line of CBD oils and edibles, said the problem is some people are relying on cannabis as "their only tool" to manage stress and anxiety.
"We see a downregulation of cannabinoid receptors," Mbengue said. "There's all of this THC floating around, and there's nothing for the THC to attach to so it can't create this calming, medicinal effect by binding to the receptors."
And longtime cannabis users who stop taking the drug may experience symptoms of withdrawal, including anxiety and depression, because the brain has come to expect the influx of cannabis compounds.
The calming effects of CBD
CBD has a similar structure to THC, but it doesn't affect the brain's reward circuitry in the same way, meaning there's less of a risk for abuse, Grubel said. There's a growing body of research supporting that CBD may be able to reduce anxiety or stress.
"There is increasing evidence that, for at least some individuals, there is absolutely some clinical benefit," Grubel said. "We certainly need more data, which we're trying very hard to collect."
One small study published last year suggests cannabis with equal parts of CBD to THC may induce less anxiety than "THC-dominant" weed.
Dani Gildemontes-Davila, a 27-year-old who lives in California and sells cannabis-related products online, said that during the workweek she usually smokes weed to combat anxiety at the end of the day, often taking a 1:1 ratio of CBD to THC. Gildemontes-Davila said she prefers weed to other prescription drugs she takes.
"I have three prescriptions," she said. "I can easily say the one with the least side effects, and the one where I still feel like me, is weed."
Regular use of CBD can affect how other drugs metabolize in the body, so people should check with a doctor or pharmacist with knowledge of cannabis if they use other medications.
Understanding the effects
Smoking a joint of cannabis isn't like sipping a glass of beer or wine, said Andrew Koudijs, the owner of a cannabis dispensary in Provincetown, Mass. Each hit of weed is "doubling your dose" and potentially doubling your high.
"Always start with one and see how it feels," said Koudijs. "A tiny inhale could get someone really high."
Doctors say vaping cannabis is safer than smoking it. Burning cannabis and breathing in the smoke exposes you to toxic chemicals from the combustion that can damage your lungs. Vaporizers, known as vape pens, heat cannabis into an aerosol without burning the plant or oil.
"You don't get all of the combustion products such as tar, benzene and polycyclic aromatic hydrocarbons," Grinspoon said. "It is a much safer inhalation option."
Vaping does come with its own health concerns, too.
For some, weed will never be enjoyable, experts say. It's the same reason people don't drink alcohol or caffeine; they just don't like how it makes them feel.
"There are individuals who will use cannabis and will say it's the only thing that helps them with their anxiety," Vandrey said. "And there are individuals who will use potentially even the same product and say that was the worst experience in my life."
Hannah Docter-Loeb contributed to this report.