Addiction Medicine Made Easy | Fighting back against addiction

Can You Overdose on Cannabis? The Answer is Yes (Update from 2023)

• Casey Grover, MD, FACEP, FASAM

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The cannabis available today is dramatically stronger than what existed in previous decades, with THC levels climbing from 1% in 1970 to 25-30% in 2025, creating serious risks particularly for young people who don't understand appropriate dosing. Dr. Grover shares how cannabis has been deliberately bred for higher potency and how new extraction techniques have created products with astronomical THC levels, leading to dangerous situations like young people consuming 60 times a reasonable dose.

• Cannabis potency has increased from 1% THC in 1970 to 25-30% THC today through selective breeding
• Modern extraction techniques allow THC to be added back into products, creating concentrations as high as 45% and above
• A recreational dose of THC is between 2.5-15mg, but products often contain hundreds or thousands of milligrams
• "Greening out" or cannabis toxicity causes symptoms like confusion, vomiting, decreased consciousness, and anxiety
• Children are especially vulnerable to cannabis toxicity due to smaller body size
• Most cannabis toxicity cases resolve within 24 hours with supportive care
• Prevention requires understanding appropriate dosing and using cannabis judiciously

To contact Dr. Grover: ammadeeasy@fastmail.com

Speaker 1:

Welcome to the Addiction Medicine Made Easy Podcast. Hey there, I'm Dr Casey Grover, an addiction medicine doctor based on California's Central Coast. For 14 years I worked in the emergency department seeing countless patients struggling with addiction. Now I'm on the other side of the fight, helping people rebuild their lives when drugs and alcohol take control. Thanks for tuning in. Let's get started. Today we are going to be talking about cannabis, and we've covered cannabis on this podcast many times. But cannabis is changing and people are not aware of those changes, particularly our youth, and it's leading to some serious issues.

Speaker 1:

I lecture professionally on drugs and alcohol all the time. Let's quickly get us all up to speed on cannabis. Cannabis is a plant and it contains multiple naturally occurring chemicals. One chemical, tetrahydrocannabinol, most often referred to as THC, is the chemical in cannabis that gets us high, and THC is what we'll be focusing on for the next little bit in this episode. I've actually created a chart that I use regularly when I lecture that shows the potency of plant cannabis over time. In 1970, the cannabis was 1% THC and now, as of 2025, the cannabis routinely is as high as 25 to 30% THC.

Speaker 1:

People often ask me how did this happen? And it was actually deliberately done by cannabis farmers to make the cannabis stronger. I often explain this to people by referencing something a little more mainstream so that it's relatable. More mainstream so that it's relatable. The analogy that I often give is that people love watermelon but don't really like having to pick out the seeds. So farmers wanted to make a seedless watermelon. So what they did is, over time, farmers bred watermelon with smaller seeds, with other strains of watermelon with smaller seeds, and when this happened, over multiple generations of watermelon, the plant changes. In other words, with farming technology, farmers can change how a plant grows. So, by selecting watermelon strains that had smaller and smaller seeds, we now have seedless watermelon. And it's the same with cannabis. Farmers bred stronger and stronger strains of cannabis and we now have very strong cannabis. Essentially, what it was is that people like THC. So farmers followed what people wanted and bred cannabis strains with more THC over and over again, making the cannabis stronger.

Speaker 1:

And furthermore, the cannabis industry has innovated. It has used chemistry to extract THC from the plant, allowing THC to be put into multiple different forms, such as edibles and drinks, and we are now seeing the cannabis industry actually put THC back into plant-based cannabis to increase the strength. So one cannabis dispensary I went to had what are called THC-infused joints, where the percentage of THC in the cannabis product was more like 45% THC. They actually took regular plant-based cannabis and then supplemented that plant-based cannabis with extra THC to make it even stronger. It's a little bit like in the alcohol industry they will add in liquor to wine to make it stronger, like adding brandy to wine to make it port. However, the issue that I have is we are now seeing cannabis products with astronomical amounts of THC and consumers are not well informed.

Speaker 1:

The recreational dose of THC, what we might think of as a single serving of THC, is not yet agreed upon. It's somewhere between two and a half and 15 milligrams of THC. But what we are seeing are products that are being sold with drastically higher amounts of THC than that potential single dose and, again, consumers really have no idea. As I mentioned, I went to a cannabis dispensary to see how this stuff was sold and one package of four cannabis-infused joints had 832 milligrams of THC in it. That is potentially several hundred times more THC than the so-called recreational dose. Now, the reason that this has been on my mind is I heard from one local school recently that they had some students get pretty sick when they used THC because they used a lot and had no idea how much the package they had contained compared to how much they might be using in terms of a recreational dose. They bought a cannabis product that had 3,000 milligrams of THC in the package. It was actually 10 individual servings of 300 milligrams and again, the recreational dose, as in a single serving of cannabis, is somewhere between two and a half and 15 milligrams of THC, and this product was saying that a single serving was 300 milligrams of THC. And these are high school students. They had no idea how much was a reasonable dose. So they looked at the package and it said it contained 10 servings. So each of them took a serving, which again was the incredibly high amount of 300 milligrams of THC. If the recreational dose of THC is five milligrams, then the package recommended that they take 60 times what actually might be that recreational dose. Put another way, that is like trying 60 beers instead of one beer the first time you try alcohol. Fortunately, the students got medical attention, but they had some serious adverse effects from consuming that much cannabis.

Speaker 1:

I go to schools very frequently and lecture about drugs and alcohol, and when I'm going to be going to schools. Going forward, I'm going to really focus on trying to give the students an idea of how much cannabis is reasonable for a person to use, compared to what is being sold, and I will likely be sharing this case in a de-identified fashion as a part of the regular lecture that I give to students and also parents, when I talk to them about drugs and alcohol. Now, if you didn't know, you can overdose on cannabis. It's often called greening out and, given what we talked about now's as good a time as any for a refresher on what a cannabis overdose looks like and how it's managed. Fortunately, we covered this topic on the podcast back in 2023. So let's go back and listen right now to our previous episode on cannabis overdose. It was a great overview of the topic. Here we go.

Speaker 1:

This episode will be on the topic of cannabis toxicity. Now why are we covering this topic? Well, I was speaking to some high schoolers at the end of last year about substance use and many of the kids had questions about greening out. I had not heard that term before, but when I asked the students to describe what it was, they told me that it was what happened when you smoked too much cannabis. A few students had experienced it and reported symptoms of confusion, sleepiness and vomiting. Reported symptoms of confusion, sleepiness and vomiting. We covered cannabis-induced psychosis on this podcast in episode 28, but what these students were referencing appeared to be something different, so it was time to figure this out. As you can guess from listening to previous episodes of this podcast, the first place I went to get more information on this topic was PubMed and fortunately, I found a paper on the topic pretty easily, and we will use that paper as part of the evidence-based backbone of this episode.

Speaker 1:

The title of the paper is Acute Cannabis Toxicity and it was published in Clinical Toxicology in 2019. The lead author is Matthew Noble. The authors begin with an introduction section in which they highlight a few points about cannabis, and we will review some of the key points that they make. The cannabis plants, cannabis sativa and Cannabis indica, contain over 60 cannabinoid compounds, the most well-known being THC and CBD. As cannabis has been legalized in more and more states here in the United States, it is being more commonly used. Furthermore, with legalization of cannabis, more formulations and preparations of cannabis are on the market, such as vape liquids, gummies, pastries and high-potency oils, resins and extracts. Some of these products, including pastries like cookies and brownies and gummies, are very attractive to children, which has resulted in increased exposure of children, often accidentally, to cannabis.

Speaker 1:

So this brings the authors to the methodology of the paper, which is an observational study of the clinical effects following acute cannabis exposures as reported to the Oregon and Alaska Poison Control Center between December 2015 and April 2017. There is quite a long methodology section describing how they were able to sort through, categorize and analyze the poison control data. But, bottom line, they reviewed all calls to this poison control center when people were exposed to cannabis and recorded what happened to those people. They excluded cannabinoid hyperemesis syndrome-related calls, calls related to animal exposures and calls that involved exposure to cannabis and exposure to another substance or multiple substances, but they did include calls that involved exposures to multiple forms of cannabis at the same time. Okay, on to the results. What did they find? Well, they found 253 cases of calls related to cannabis exposure.

Speaker 1:

These exposures to cannabis occurred in people from 8 months of age to 96 years of age and the mean age was 25. 54% of exposures occurred in males. Most calls did not provide a quantitative amount of cannabis consumed, but when there was an amount. Reported exposures varied from 2 mg to 1,000 mg of THC. Most subjects were exposed to 15 to 50 mg of THC and all of the cases requiring hospital admission involved exposures to 15 mg of THC or more. Now a quick aside For your reference most recreational cannabis doses are between 2.5 mg and 15 mg of THC. 5 mg of THC has been proposed as a potential standard dose for recreational use. Back to the article.

Speaker 1:

The authors move on to describe some of the trends they identified in the data. First, they looked at acute cannabis exposures by age. In kids under 12, edibles were the most common exposure and nearly all exposures in this group were accidental. Interestingly, kids under 12 who were exposed to cannabis were less likely to develop tachycardia than adolescents or adults. In 90% of exposures, patients of all ages exposed to cannabis experienced adverse clinical effects. Neurotoxicity was the most common in all groups. Children under 12 were more likely to present with CNS depression. Adults were more likely to present with CNS excitation and adolescents had an equal split of CNS excitation and CNS depression.

Speaker 1:

Some examples of the CNS excitation syndromes would include paranoia, anxiety, panic attacks or hallucinations, and some examples of the CNS depression symptoms would include ataxia, speech abnormalities, decreased loss of consciousness and obtundation, and obviously, cns refers to the central nervous system. Most patients did not require any specific treatment. A small number of adults and adolescents required benzos for CNS excitation and a small number of adults and adolescents required antiemetics for nausea and vomiting. Adults and adolescents required antiemetics for nausea and vomiting. Now, in terms of critical illness, three patients in this cohort were intubated as a result of their exposure. Two of these were infants and one was an adult, and all three were exposed to high THC preparations. All developed severe CNS sedation and respiratory depression, with one of the infants having respiratory failure. All three were extubated within 24 hours and recovered well.

Speaker 1:

The authors move on to looking at how different preparations of cannabis affected presentation. When plant material was consumed, cns depression was more common than CNS excitation. When cannabis was smoked and inhaled, many subjects developed. Tachycardia and CNS excitation was more common than CNS depression. When cannabis was consumed as an edible, cns depression. When cannabis was consumed as an edible, tachycardia was less common than when cannabis was smoked and with edibles, cns depression and excitation were both seen. When cannabis was consumed as a high THC concentration resin that's a solid there were higher rates of CNS excitation and tachycardia as compared to other routes. When cannabis was consumed as a high THC concentration liquid, there were also higher rates of CNS excitation and tachycardia as compared to other routes. And finally, high THC concentration formulations of cannabis were more associated with intubation than other forms of cannabis.

Speaker 1:

Now the authors of the article have a lot of great tables in the article, including a table detailing the clinical effects of acute cannabis exposure by age and by cannabis product type cannabis exposure by age and by cannabis product type. They also have a chart that describes in detail each of the cases that were admitted to an ICU after cannabis exposure. To avoid this episode getting too long, I won't review each table in detail, but feel free to check out the paper and take a look for yourself. However, there are a few points that I wanted to call out from these charts. First, there were eight cases that required ICU admission, which was a little over 3% of all the cases they reviewed. There was one death, which occurred in a 70-year-old man, and this accounted for 0.4% of all the cases they reviewed. He vaped a high THC concentration liquid, then developed a wide, complex tachydysrhythmia and ST elevation on EKG. Autopsy revealed acute MI in the setting of multivessel coronary artery disease.

Speaker 1:

There was also a very wide variety of symptoms that people experienced and that's reported in Table 2 of the article. They broke down symptoms into several categories, with specific symptoms listed in each category. Let's go through them to get a sense of just how many different symptoms people experienced with cannabis exposure. Cns excitation People experienced anxiety, paranoia, hallucinations, agitation, psychosis, seizure and tremors. Cns depression People experienced decreased level of consciousness, coma, syncope, confusion, ataxia and slurred speech. Other neurotoxicity People experienced confusion, dysphoria, abnormal sensation, numbness, headache and lightheadedness. Cardiac People experienced palpitations and chest pain. Gi People experienced nausea, vomiting, diarrhea and abdominal pain. Respiratory People experienced respiratory depression, dyspnea and cough. And finally, some people also experienced hyperthermia. Here were the top five individual symptoms from that list that I just went through. The number one symptom was nausea and vomiting, which occurred in 25% of patients exposed to cannabis. Number two was decreased level of consciousness, which occurred in 23% of patients exposed to cannabis. Number three was anxiety, paranoia or panic, which occurred in 22% of patients exposed to cannabis. Number four was palpitations, which occurred in 12% of people exposed to cannabis. And number five was confusion, which occurred in 10% of patients exposed to cannabis. So a wide variety of symptoms were experienced after exposure to cannabis.

Speaker 1:

The authors move on to the discussion section, and we will hit the high points of the discussion section. The authors note that neurotoxicity was common following cannabis exposure, with variable presentations. Cns depression was more common in pediatric patients, and the authors postulate that this may be because the weight-based dose of cannabis is greater in pediatric patients due to their small size. The authors follow this by noting that there was an increased risk in respiratory depression and intubation when concentrated THC products were consumed, particularly in children. The authors synthesize these two points to highlight the increased risk with cannabis exposure in children as compared to adults, and that greater efforts to reduce children's risk of cannabis exposure should be undertaken. The authors also note that when children were exposed to cannabis, it was most often accidental and the exposure to cannabis most often came from a cannabis product belonging to a family member.

Speaker 1:

Okay, so that is the end of the first article. I think the article corroborates what I expected to be the case. Kids are more vulnerable to cannabis toxicity. Edibles are appealing to kids and account for the majority of exposures in kids, and high THC concentration products have a greater risk of toxicity in all age groups. Now, this was obviously helpful information, but I still felt like I needed more information on cannabis toxicity, so I went back to PubMed and found a second article, which was published in StatPearls in 2022. The title was Cannabinoid Toxicity and the lead author was Brian Kelly. This second article covers a lot of the same topics as the first article, so I will hit the highlights. The authors of this article address the pathophysiology of cannabis toxicity, which it sounds like has not been fully worked out.

Speaker 1:

There are two cannabinoid receptors in the body that are part of the endocannabinoid system CB1 and CB2, both of which are G-protein-linked receptors. Cb1 receptors are mostly located in the brain, while CB2 receptors are mostly located in the periphery. Stimulation of CB1 receptors in the brain leads to a modulation of various neurotransmitters, including acetylcholine glutamate, gaba, dopamine, norepinephrine and serotonin. While the exact details have not been worked out, excessive stimulation of CB1 receptors by cannabis, such as with an accidental ingestion or acute heavy use, puts all of these neurotransmitters out of balance due to the effects of the CB1 receptors, and the cannabinoids found in natural cannabis are only partial agonists at the CB1 and CB2 receptors. Synthetic cannabinoids are full agonists at the CB1 and CB2 receptors and thus cause even more stimulation of CB1 in the brain, which is why synthetic cannabinoids are more likely to cause toxicity than natural cannabis.

Speaker 1:

Moving on to the toxicokinetics of cannabis toxicity, the authors note, quote the toxic effects of cannabinoids are secondary to overstimulation of the endocannabinoid system. End quote. The authors note up to four hours after oral consumption. The duration is also dependent on the route of use lasting two to six hours after inhalation and lasting eight to 12 hours after oral consumption. The authors move on to the signs and symptoms of cannabis toxicity, which we covered extensively in Article 1, so I will just add one additional note from this section. Cannabis toxicity can also, due to the changes in neurotransmitter function from overstimulation of the CB1 receptor in the brain, cause sympathomimetic toxicity. This can include, in severe cases, rhabdomyolysis, hyperthermia, seizures and renal failure.

Speaker 1:

The authors conclude this second article with a discussion of the treatment of cannabis toxicity. Quote. Treatment of cannabinoid toxicity is largely supportive and focuses on symptomatic and supportive care. Most adult patients with cannabis toxicity improve on their own with observation. End quote. For pediatric patients, the authors note that there is a higher risk of toxicity and observation may need to be for longer. Also, social services may need to be involved to ensure that the home environment is safe.

Speaker 1:

When there is severe cannabis toxicity, the authors recommend benzodiazepines and antipsychotics to address agitation, hallucinations and psychosis. Tachycardia can be managed with benzodiazepines and IV fluids. Considering that cannabis toxicity can cause sympathomimetic toxicity, patients with vascular risk factors may need to be evaluated for cardiac ischemia. Seizures obviously would be treated with benzodiazepines. The authors note that most patients can be observed for six hours for improvement and or resolution of symptoms and discharged home if improved. For CNS, depression, confusion, seizures or persistently abnormal vital signs, patients may need admission. When edible products are consumed, observation may need to be longer due to the longer duration of effects from edibles. If patients do not clear or return to baseline, then obviously further workup would be needed, as cannabis toxicity will resolve on its own once the cannabis is metabolized. And that concludes our second article on cannabis toxicity.

Speaker 1:

Now, before we wrap up this episode, I wanted to go back to this term greening out that I heard from the high school students that I was talking to. I searched the term on PubMed and found nothing. So I went to a general internet search. I found an article written by a treatment program called Boca Recovery Center, entitled what is Greening Out. This is not a peer-reviewed article, so take the information from the article with a grain of salt, but the article did list several scientific articles as references, so there's at least some component of evidence-based information here.

Speaker 1:

Let's dig in to this article. The article begins with the simple statement quote greening out occurs when an individual mixed with other drugs or alcohol. The symptoms of greening out are described as pale skin, nausea, vomiting, dizziness, disorientation, anxiety, panic and, in severe cases, hallucinations. As an aside, if those symptoms sound familiar, it's because they are the symptoms of cannabis toxicity described in the first article. Moving on, this third article notes that greening out comes from ingesting high amounts of cannabis or THC-containing products and that the risk of greening out increases with the use of high THC-containing products. Again consistent with the first article we reviewed from PubMed, this third article moves on to note that regular cannabis use will cause tolerance to cannabis and the risk of greening out increases when a large amount of cannabis is used in individuals with low or zero tolerance.

Speaker 1:

The article moves on to a brief section on what do you do if you green out, and it's pretty simple. The article counsels that most episodes of greening out will resolve within 24 hours and that intense symptoms should prompt seeking medical attention. The article recommends that mild or moderate symptoms be managed with rest, lying down, oral hydration and, if not too nauseated, eating a meal. Next, the article discusses how to prevent greening out, and it's very simple Quote the best way to prevent greening out is to use cannabis products judiciously. Do not consume too much. End quote. The article also points out that it may take a while to feel the effects of edible cannabis, so consuming multiple doses of edible cannabis back-to-back should be avoided. The article concludes with some information for patients on cannabis use disorder and the treatment for cannabis use disorder. Okay, so we've done a pretty good review of this topic. Cannabis use disorder. Okay, so we've done a pretty good review of this topic.

Speaker 1:

Let's wrap up this episode on cannabis toxicity and greening out with some take-home points. Number one cannabis toxicity is the result of overstimulation of the endocannabinoid system, which causes disruption of the normal function of multiple neurotransmitter systems in the brain. Number two functionally, cannabis toxicity can be thought of as a cannabis overdose, as it is the result of consuming enough cannabis to overstimulate the endocannabinoid system. For individuals who consume cannabis regularly and have tolerance, it will take more cannabis to cause toxicity compared to those who do not have tolerance, such as children. 3. The top five symptoms of cannabis toxicity reported in one paper were nausea and vomiting, decreased level of consciousness, anxiety, paranoia or panic, palpitations and confusion. Number four as cannabis affects multiple systems of the body, cannabis toxicity can manifest in multiple ways, affecting the neurologic, cardiac, gastrointestinal and respiratory systems. Number five in children under 12, most episodes of cannabis toxicity are due to accidental exposures to edibles.

Speaker 1:

6. The risk of cannabis toxicity and the severity of cannabis toxicity are increased in children due to their small body size and when high THC concentration products are used. When high THC concentration products are used. 7. The onset and duration of cannabis toxicity varies by route of use, with the time to onset and duration after consumption being longer with edible cannabis products. 8. Treatment of cannabis toxicity is supportive, with nearly all cases resolving within 24 hours and most cases resolving within 24 hours and most cases resolving within six hours. And number nine greening out is a term used to refer to cannabis toxicity in the cannabis-using community.

Speaker 1:

Before we wrap up, a huge thank you to the Montage Health Foundation for backing my mission to create fun, engaging education on addiction and a shout out to the nonprofit Central Coast Overdose Prevention for teaming up with me on this podcast. Our partnership helps me get the word out about how to treat addiction and prevent overdoses To those healthcare providers out there treating patients with addiction. You're doing life-saving work and thank you for what you do For everyone else tuning in. Thank you for taking the time to learn about addiction. It's a fight we cannot win without awareness and action. There's still so much we can do to improve how addiction is treated. Together we can make it happen. Thanks for listening and remember treating addiction saves lives.