If you're reading this while it's happening, or sitting with someone it's happening to: this almost certainly passes on its own, and people very rarely come to serious harm from it. The part worth knowing is the small number of situations where what looks like greening out is something else.
Key Takeaways
- Greening out is unpleasant and frightening, but not typically dangerous
- Cannabis doesn’t suppress breathing the way opioids do — that’s an anatomical difference, not luck
- Several dangerous things look identical: CHS, a cardiac event, or a product containing something else
- Edibles cause this most, because the delay between taking and feeling breaks the feedback loop
What Greening Out Is
The informal name for taking more cannabis than your body copes with comfortably. It typically involves going pale and clammy, dizziness, nausea and sometimes vomiting, a racing heart, and a wave of anxiety or paranoia — often with a powerful conviction that something has gone badly wrong.
That last part is worth naming, because it's frequently the worst of it. The physical symptoms are unpleasant; the sense of dread is what makes people call for help. Knowing that the fear itself is a predictable effect — not evidence that something is actually wrong — genuinely helps.
Why It Isn't Fatal
There are no confirmed cases of adults dying from cannabis alone the way people die from opioid overdose, and the reason is structural rather than lucky. The brainstem regions that control breathing carry very few cannabinoid receptors — so cannabis doesn't switch off respiration the way opioids and sedatives can [1].
That's a real and meaningful difference. It is not the same as cannabis being harmless. People are injured in accidents and falls while badly impaired, heavy long-term use carries its own consequences, and edible ingestion by a child is a genuine emergency because the dose relative to body size is enormous.
What It Might Not Be
This is the part most pages on this topic skip, and it's the reason a reassuring answer alone isn't good enough. "It's just greening out, wait it out" is right most of the time and wrong in ways that matter:
Cannabinoid hyperemesis syndrome
Repeated severe vomiting in someone who uses cannabis heavily and long-term — especially with a compulsion to take very hot showers — is more likely CHS than a one-off greening out. It recurs, and it resolves only with stopping.
A cardiac event
Cannabis raises heart rate. Chest pain, pressure, or a genuinely irregular heartbeat should not be attributed to being too high — particularly in anyone with existing heart concerns, or where stimulants may also be involved.
Something else in the product
An edible or vape from an informal source may contain more than cannabis. Unresponsiveness or slowed breathing is not the greening-out picture and points elsewhere — give naloxone if available and call 911.
A panic attack
Racing heart, chest tightness, and a conviction that something is terribly wrong overlap almost completely. Not more dangerous — but it responds to reassurance and slow breathing rather than waiting it out, and it can recur without cannabis.
The first one is worth dwelling on because it's so often missed. If someone is vomiting repeatedly and this keeps happening — particularly if they're using cannabis heavily and find hot showers are the only relief — that's the picture of cannabinoid hyperemesis syndrome, not a one-off. It's frequently misdiagnosed for years, and it only resolves with stopping.
Why Edibles Do This Most
Almost every bad cannabis experience has the same structure behind it, and it isn't recklessness — it's a broken feedback loop.
Inhaled cannabis produces effects within minutes, so people self-regulate naturally: you feel it, you stop. Edibles have to pass through the digestive system first, so nothing happens for a considerable while. Someone concludes it isn't working and takes more. Then the whole amount arrives together — a dose far beyond anything they'd have chosen deliberately, arriving faster than they can adjust to.
Rising product potency compounds this, and homemade or informally-sold edibles have no reliable labelling at all. It's why a person who has used cannabis for years without incident can green out badly on their first edible.
What Actually Helps
Somewhere calm, cool, and quiet. Sitting or lying down — fainting is a real risk, particularly on standing. Sips of water. Someone staying with them, saying clearly and repeatedly that this passes, because reassurance from a calm person does more than anything else available.
If they vomit while lying down, get them on their side. Don't add caffeine, alcohol, or anything else to counteract it — nothing does, and stimulants make the racing heart and anxiety worse. And don't let them drive, for considerably longer than they'll think is necessary.
When to Call 911
Chest pain or pressure. Real difficulty breathing. Unresponsiveness, or being unable to rouse them. A seizure. Vomiting that won't stop. Or any suspicion that the product contained something other than cannabis.
That last one deserves emphasis. Slowed or shallow breathing is not the greening-out picture, and it points toward something else — give naloxone if it's available and call 911. Fentanyl can't be seen, smelled, or tasted [3], and naloxone causes no harm if no opioid is present. Being wrong about that costs nothing; being right matters enormously.
And a child who has eaten an edible needs emergency care straight away, whatever they seem like at the time.
If it keeps happening
A one-off is a bad night. A pattern is information — whether that's repeated greening out, using more to get the same effect, or cannabis having stopped being enjoyable while remaining hard to stop.
Cannabis is very often doing a job: managing anxiety, sleep, or a mood that predates it. Where that's the case, treating the substance use and what sits underneath together is what holds — removing one without the other usually doesn't. Our work centres on co-occurring mental health conditions alongside substance use. If you're a parent worried after an episode like this, our Families & Loved Ones team can help you approach it.
Call 911 for chest pain, trouble breathing, unresponsiveness, seizure, or vomiting that won't stop — and give naloxone if available in case something else is involved. A child who has eaten an edible needs emergency care immediately. If this brings up thoughts of suicide or self-harm, call or text 988.
FAQs
- What does greening out mean?
- It is the informal term for taking more cannabis than your body handles comfortably — producing dizziness, nausea, vomiting, pallor, sweating, a racing heart, anxiety or paranoia, and sometimes a strong feeling that something is seriously wrong. It is unpleasant and frightening rather than typically dangerous.
- Can you fatally overdose on marijuana?
- There are no confirmed cases of adults dying from cannabis alone in the way people overdose on opioids. The reason is anatomical: the brainstem areas controlling breathing have very few cannabinoid receptors, so cannabis does not suppress breathing the way opioids and sedatives do. That is a real difference, not reassurance — but it does not make cannabis harmless.
- How long does greening out last?
- It depends heavily on how it was taken. Inhaled cannabis peaks and fades comparatively quickly; edibles take much longer to come on and last considerably longer, which is why an edible experience can feel endless. Residual grogginess can persist into the next day. If symptoms are not easing at all over hours, that is worth medical attention.
- What should I do if someone is greening out?
- Keep them somewhere calm, cool, and quiet. Sit or lie them down — fainting risk is real, especially standing up. Offer sips of water. Stay with them and keep reassuring them it will pass, because the fear is often worse than the physical symptoms. If they vomit while lying down, put them on their side.
- When does greening out need emergency care?
- Call 911 for chest pain, difficulty breathing, unresponsiveness or inability to rouse them, a seizure, or vomiting that will not stop. Also call if you suspect the product contained something other than cannabis. These are outside the ordinary picture.
- Does greening out cause brain damage?
- There is no evidence that an acute episode of greening out causes lasting brain damage. That is a separate question from the effects of heavy long-term use, particularly in adolescence, which is an area of ongoing research and genuine concern.
- Why do edibles cause this so often?
- Because the feedback loop is broken. Inhaled cannabis produces effects within minutes, so people naturally stop when they have had enough. Edibles take substantially longer to take effect, so someone who feels nothing takes more — and then all of it arrives at once. The dose that lands is far larger than anything they would have chosen.
- Does insurance cover treatment for cannabis use and mental health?
- Most major plans cover medically necessary treatment for substance use and mental health conditions together. You can verify coverage for free in a few minutes.
Sources
- National Institute on Drug Abuse (NIDA). Cannabis (Marijuana).
- Sorensen CJ, et al. Journal of Medical Toxicology (2016), NIH/PMC. Cannabinoid Hyperemesis Syndrome: Diagnosis, Pathophysiology, and Treatment — a Systematic Review.
- National Institute on Drug Abuse (NIDA). Fentanyl.
- National Institute of Mental Health (NIMH). Panic Disorder.
This article is for informational purposes only and is not a substitute for professional medical advice. If symptoms are severe or you are unsure, seek medical care.
Written by
Executive Director
Dominic Perry is a Licensed Clinical Social Worker (LCSW), Licensed Clinical Alcohol and Drug Counselor (LCADC), Master Addiction Counselor (MAC), and DOT Substance Abuse Professional (SAP) with approximately eight years of experience in behavioral health and substance use treatment. Dominic began his work with Virtue as a therapist at the Corbett residential facility before progressing into leadership, and now serves as Executive Director of Virtue Recovery Center – Outpatient in Las Vegas. He earned his Bachelor of Social Work from UNLV and his Master of Social Work from the University of Nevada Reno.
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