Cannabis poisoning happens when someone consumes enough THC to cause symptoms beyond a normal high, ranging from severe anxiety and vomiting to dangerously slowed breathing. In 2024, an estimated 1,089,579 cannabis-related emergency department visits occurred in the United States, with the highest rate among adults aged 18 to 25. While fatal overdoses from cannabis alone remain extremely rare, the experience can be frightening and, in certain cases involving children or people with heart conditions, genuinely dangerous.
How Cannabis Poisoning Differs From Getting High
Normal cannabis intoxication produces relaxation, mild euphoria, sleepiness, dry mouth, red eyes, and some short-term memory impairment. Cannabis poisoning occurs when the dose crosses a threshold where unpleasant or harmful effects take over. At that point, symptoms shift from pleasantly altered to genuinely distressing.
Large doses of THC can cause confusion, amnesia, delusions, hallucinations, intense anxiety, agitation, and slurred speech. Physical symptoms include poor coordination, decreased muscle strength, slowed reaction time, and drops in blood pressure when standing up. Most episodes resolve on their own relatively quickly, but while they’re happening, the person may feel like something is seriously wrong.
Panic attacks and brief psychotic episodes are more common in first-time users and people with a history of psychiatric conditions. These episodes are temporary, but they’re the main reason people end up in emergency rooms after using cannabis.
Why Edibles Cause Most Poisoning Cases
Edibles carry a higher poisoning risk than smoked cannabis because of how the body absorbs them. When you smoke or vape cannabis, effects hit within minutes, making it relatively easy to stop before overdoing it. Edibles take 30 minutes to 2 hours to produce noticeable effects. During that window, many people assume their dose wasn’t enough and eat more, only to have the full combined dose hit all at once.
The resulting intoxication is often more intense and lasts significantly longer than expected. Factors that amplify the effect include eating edibles on an empty stomach, drinking alcohol at the same time, and taking certain medications. Legal edible products in Canada are capped at 10 mg of THC per package, but unregulated products can contain far more, sometimes with little accuracy in their labeling.
Symptoms in Children
Accidental ingestion by children is one of the most concerning forms of cannabis poisoning. Kids are smaller, their brains are still developing, and they can’t communicate what they’re feeling. Edible cannabis products that look like candy, cookies, or gummy bears are the usual culprit.
In children under 12, the most common signs are lethargy, limp or floppy muscles, rapid heart rate, unsteadiness, and dilated pupils. Vomiting and slowed breathing also occur. Seizures are possible, though rare. Some children show the opposite of what you’d expect: hyperactivity and irritability rather than sedation. If a child has potentially consumed any cannabis product, this is always a medical emergency, regardless of how much you think they ate.
Heart-Related Risks
THC stimulates the nervous system in ways that can affect heart rhythm. The most common cardiovascular effect is a rapid heart rate, which most healthy people tolerate without problems. But in rare cases, cannabis use has been linked to more serious rhythm disturbances, including prolonged electrical signaling intervals in the heart that can set the stage for dangerous arrhythmias.
Case reports have documented ventricular fibrillation (a life-threatening heart rhythm) in young adults after cannabis use. One published case involved a young woman whose heart rate climbed to 122 beats per minute with abnormal electrical patterns on her heart tracing. These events are uncommon, but they’re worth knowing about if you have an existing heart condition or a family history of heart rhythm problems.
Delta-8 THC Carries Similar Risks
Delta-8 THC, which is sold in many states with fewer restrictions than traditional cannabis, is roughly 50 to 75 percent as potent as standard (delta-9) THC. That lower potency can create a false sense of safety. Delta-8 can cause the same poisoning symptoms: lethargy, uncoordinated movement, slurred speech, rapid heart rate, low blood pressure, difficulty breathing, and sedation.
The CDC has flagged pediatric cases involving delta-8 products where children experienced deep sedation, slowed breathing, and heart rate changes progressing from fast to dangerously slow. Because delta-8 products are often unregulated, their actual THC content and purity are unpredictable.
Cannabinoid Hyperemesis Syndrome
Cannabinoid hyperemesis syndrome, or CHS, is a different kind of cannabis-related illness that affects long-term, frequent users. Rather than a single episode of taking too much, CHS develops over months or years of regular use and causes cycles of severe nausea, intense abdominal pain, and relentless vomiting that can reach up to five times an hour. Some people experience what’s been called “scromiting,” a combination of screaming and vomiting driven by extreme pain.
CHS typically unfolds in three phases. The prodromal phase involves morning nausea, stomach discomfort, and a fear of vomiting without actually throwing up. This can last months or even years. The hyperemetic phase is the crisis stage, usually lasting 24 to 48 hours, with overwhelming nausea and recurrent vomiting. During this phase, many people discover that long, hot showers or baths are the only thing that provides relief, and they may shower compulsively for hours. The recovery phase follows when cannabis use stops, with symptoms gradually fading over days to months.
CHS is most common in adults who started using cannabis as teenagers and have continued for years. The only effective long-term treatment is quitting cannabis entirely. Standard anti-nausea medications often don’t work for CHS, which is one reason it’s frequently misdiagnosed before the cannabis connection is identified.
What Happens at the Hospital
Treatment for cannabis poisoning is supportive, meaning there’s no antidote. The goal is to keep you safe and comfortable while the THC works its way out of your system. For most adults, this means being placed in a quiet room with monitoring of heart rate and blood pressure. If anxiety or agitation is severe, sedative medications may be used to calm things down.
For children who have recently swallowed a large amount, doctors may consider measures to reduce absorption from the stomach, but only within the first couple of hours. For CHS patients, a capsaicin-based cream applied to the abdomen has shown some benefit in reducing nausea, alongside stronger sedative medications when standard anti-nausea drugs fail.
Most people recover fully within hours, though edible-related episodes can stretch longer due to the slower way the body processes ingested THC. The lingering effects, such as feeling foggy or off-balance, typically clear within a day.