Cannabis-Associated Emergencies in the Emergency Department

Background: Now that the Cannabis Act legalizing the use of cannabis has come into effect in Germany, the frequency of cannabis use in Germany may rise, and with it the number of cannabis-related visits to emergency departments.

Methods: In this narrative review, we identify and evaluate the observed trends in case numbers after cannabis legalization in other countries, the common reasons for emergency department visits, and the options for treatment. Data on trends in cannabis-related emergency contacts in Germany were provided by the Poison Control Center North and are evaluated descriptively.

Results: The prevalence of cannabis use in Europe is estimated at 8%. In Canada, after legalization, cannabis use among the total population aged 15 years and over rose from 15% in 2017 to 25% in 2021, and hospital admissions doubled from 15/100 000 in 2017 to 32/100 000 in 2022. Acute intoxication is the most common reason for hospital admission and is often accompanied by acute anxiety and panic attacks. The risk of developing psychosis increases with THC content and frequency of use. Cannabinoid hyperemesis syndrome manifests itself with abdominal pain and severe, cyclical vomiting. The most important acute measure is to replace the often massive fluid loss. Benzodiazepines and antipsychotic drugs can be given as symptomatic treatment.

Conclusion: The legalization of cannabis use can be expected to lead to an increase in cannabis-related emergencies in Germany as well. As the clinical manifestations are often nonspecific, the targeted investigation of possible cannabis use is indicated so that the affected patients can be given appropriate treatment and assistance.

Cite this as Eichhorn D, Schaper A, Iwersen-Bergmann S, Ondruschka B, Weber-Papen S, Bernhard M: Cannabis-associated emergencies. Dtsch Arztebl Int 2025; 122: 467–71. DOI: 10.3238/arztebl.m2025.0074

In April 2024, the German Cannabis Act (Cannabisgesetz, CanG) came into effect. The CanG makes it legal for adult users to obtain 50 g cannabis per month through membership in what are referred to as cultivation associations (Anbauvereinigungen). Private self-cultivation of up to three cannabis plants is now also legal. In this way, the Federal Government aims to counter the increasing use of uncontrolled cannabis available on the black market. Decriminalization is intended to improve consumer protection through better control of cannabis quality, the Δ9-tetrahydrocannabinol (THC) content of plants, and possible contaminants (1, 2). The aim is to protect the particularly vulnerable target group of adolescents through awareness campaigns, a ban on use for under-18-year-olds, and protected zones around schools and sports facilities. Whether these measures are actually sufficient is the subject of considerable critical debate, particularly among pediatric specialists (3). However, given the recent nature of the amendment, an empirical analysis will only be possible in the coming years.

Any estimate of the potential additional burden on emergency departments also remains largely speculative at this point. In a press release based on insurance data from 2022 alone, the Kaufmännische Krankenkasse (a German health insurance provider), reported 209 000 outpatient visits due to intoxication, dependence, or withdrawal symptoms following cannabis use. This represents a three-fold increase in the number of patients since 2012—it should be noted, despite a ban on use up to this point (4).

The CanG has made it legal to consume several joints per day. It remains to be seen whether, since the enactment of the new law, the number of outpatient visits stagnates or even declines as a result of improved product quality and greater control over the black market. However, studies from Canada and the USA, where cannabis use has been legal for years, show an increase in patients presenting to emergency departments due to anxiety attacks, psychosis, and cyclical vomiting (5, 6). Therefore, with a focus on these countries, this article aims to identify and critically discuss the relevant acute pathologies and possible treatment strategies.

Methods

For this narrative review, a selective literature search was conducted using PubMed to identify relevant meta-analyses, studies, reviews, guideline reports, and statements from professional societies. The data were evaluated for trends in case numbers after cannabis legalization in other countries such as Canada and the US, the most common reasons for emergency department visits, and the options for emergency treatment. Data on trends in cannabis-related emergency contacts in Germany were provided by the Poison Control Center North (Giftinformationszentrums Nord) and evaluated descriptively.

A look beyond national borders

Depending on the study, there are between 190 and 228 million cannabis users worldwide (7, 8, 9). The prevalence in Europe is estimated at 8%, or 22.6 million people (8, 10). One in four European adults has tried cannabis at least once (11). The number of countries where consumption is legal is steadily rising (9). Canada and the US are suitable countries for comparison, given that cannabis use has been legal there for several years now and a wealth of empirical studies on the subject is available.

Cannabis consumption was legalized nationwide in Canada in October 2018 (5). Since then, adults have been permitted to purchase cannabis from licensed retailers, possess 30 g of cannabis, and cultivate up to four cannabis plants. After its legalization, cannabis use among the total population aged 15 years and over rose steadily from 15% in 2017 to 25% in 2021 (5). The number of hospital admissions doubled from the low level of 15/100 000 in 2017 to 32/100 000 in 2022 (5). In the neighboring US, the 11 states that have legalized cannabis use to date saw a 1-month prevalence of 16.93% among the total population aged 12 and over compared to 11.66% in the rest of the country (12). The number of hospital admissions rose from 12.3/100 000 in 2006 to 34.7/100 000 in 2022 (13).

In Germany, two large studies on cannabis use have been published in the context of the planned legalization: The Cannabis Potenzial und Risiken Studie (CaPRis; cannabis potential and risks study) conducted in 2019 reported a prevalence of 6.1%—or 3.1 million users—relative to the total population. In the relevant target group of 18- to 25-year-olds, nearly one in five (17.6%) had used cannabis in the past year (13). In the particularly vulnerable target group of 13- to 17-year-olds, one in eight had already tried cannabis at least once prior to its legalization (14).

The second study, conducted by the German Institute for Interdisciplinary Addiction and Drug Research (Institut für interdisziplinäre Sucht- und Drogenforschung, ISD) identified 45 studies on the effects of legalization on consumption behavior. Of these studies, 71% found that use had increased, while 29% saw no change (15). Thus, the authors concluded that if the legal situation were similar to that in the US and Canada, an increase in THC consumption could be expected in Germany following legalization. This, in turn, would likely result in an increase in emergency department visits by symptomatic patients. It remains to be seen to what extent the ban on the sale of THC-containing foods, commonly referred to as edibles (for example, THC-containing cookies, cakes, and gummy candies), can counter this trend. Initial figures from the Poison Control Center North for 2024 show an increase in cannabis-related contacts compared to the same periods in 2020–2023 (Figure). Due to the short observation period, it is not currently possible to say whether this trend will continue or even increase, and whether the change will prove to be statistically significant.

Figure

Cannabis-related calls to the German Poison Control Center North (Giftinformationszentrum [GIZ]-Nord) during the reference period from January to December 2020–2024

Mechanisms of action of cannabis

The term “marihuana” refers to the dried flowers and leaves of female plants belonging to the species Cannabis sativa and C. indica, while the term “hashish” refers to the concentrated cannabis resin (16). The psychoactive effect is primarily due to the cannabinoid Δ9-THC, which, as a partial agonist that binds to cerebral CB1 receptors, can induce euphoria, relaxation, reduced inhibition, logorrhea, and indifference (17, 18). Somatic responses include vasodilation with conjunctival redness, mydriasis, dry mouth, tachycardia, increased appetite and libido, analgesia, and antiemetic effects (17, 18). The latter properties in particular form the basis for the medical use of cannabis. Since early 2017, the Act Amending the German Narcotic Drugs Act and Other Regulations has made it possible to use THC-containing medications in Germany for the treatment of patients who continue to experience symptoms with the standard therapies available. The use of cannabis as a medicinal product—alongside the perception that it is a natural product—is undoubtedly responsible in part for the fact that it is seen by the general public as less dangerous than other intoxicants (19). However, this perception should not belie the fact that undesirable side effects can have a significant negative impact on users and ultimately lead to medical emergencies (5, 15).

Not only personal disposition but also the frequency of use, the THC content of the products, and the mode of use appear to influence tolerance and the development of undesirable symptoms. When cannabis is smoked, THC concentrations in the blood peak within a few minutes and then drop rapidly. Thus, the drug takes effect fast, with this effect diminishing over a period of around 3 h. Following oral consumption (for example, of cannabis-infused baked goods), plasma concentrations rise more slowly, not reaching a significantly lower peak until 1–2 h later, which then declines only slowly. This means that the effect persists for significantly longer (up to 12 h) (20). Relative to the number of hospital admissions, oral use of cannabis appears to have more negative effects than inhalation. Monte et al. (21), who compared the two modes of use in their study, showed that while the sale of edibles in Colorado accounted for only 0.32% of the total market, it was responsible for 10.7% of hospital visits. Edibles—irrespective of whether they are purchased or homemade—represent the main source of accidental poisonings among children (20).

From the emergency department perspective

The symptoms most likely to lead to a hospital visit by adult patients include acute intoxication, which may be accompanied by a variety of psychological symptoms, as well as chronic effects of use, such as acute psychosis, withdrawal symptoms, or cannabinoid hyperemesis syndrome (CHS).

If there are clinical signs of intoxication, in-hospital laboratory tests can confirm this suspicion within a few hours. Typically, this is carried out in the emergency setting using immunochemical testing to detect the total amount of THC and the inactive THC metabolite, THC carboxylic acid, in urine and blood. In cases where only immunochemical testing is used, the significance of the results in terms of assessing an acute effect is greatly limited by the long detectability of THC carboxylic acid, which can persist for up to 3 months (in extreme cases), particularly if there is a history of regular use. Certain medications, such as proton pump inhibitors and promethazine, can cause false-positive results in immunochemical tests (20, 22).

Acute cannabis intoxication

Acute anxiety or panic attacks are the most common manifestations of acute cannabis intoxication. Other symptoms are summarized in the Table (18, 23). These effects are possible even after one-time use of cannabis (typically with a high THC content) and often affect inexperienced users (23, 24). In most cases, treatment aimed solely at managing symptoms is sufficient. Patients should, if possible, be taken to a shielded area of the emergency department and reassured about the harmlessness of their symptoms. Consistent with the pharmacokinetics of cannabis, adverse effects are expected to subside within 3–5 h after inhalation and 8–12 h after oral intake. If patients experience severe symptoms and significant mental distress, one can primarily consider administering benzodiazepines (for example, a single dose of lorazepam, 1–2.5 mg p. o., i.m., or i.v.) as supportive treatment. If symptoms are predominantly psychotic in nature, antipsychotic drugs (for example, haloperidol, 0.5–5 mg i.m. or orally) can be used either as an add-on or as monotherapy (25).

Table

Symptom presentation and treatment options for acute clinical pictures following cannabis use*

Effects of chronic use

Acute cannabis intoxication needs to be distinguished from psychosis resulting from chronic cannabis use, since the symptoms can be strikingly similar. A recent meta-analysis showed that the risk of developing psychosis was more than twice as high compared to the general population (odds ratio [OR] = 2.47, 95% confidence interval: [1,65; 3,71]), particularly in the case of regular and frequent use from a young age and high THC content of the cannabis used (26, 27). It is important to bear in mind here that the development of psychosis is multifactorial, and confounders such as childhood trauma, multidrug use, and certain genetic factors increase both the likelihood of cannabis use and the risk of psychosis (27).

Regular use during adolescence, in particular, can result in irreversible cognitive impairments to memory and learning ability (referred to as amotivational syndrome) (28). The gateway hypothesis, according to which cannabis use promotes the use of other addictive substances, has not been proven as yet (29). In addition to the direct effects of continued use, abrupt discontinuation can also lead to effects such as withdrawal symptoms that require treatment (20). Unlike acute intoxications, the treatment and differential diagnostic classification of the effects of chronic use should be performed in a qualified psychiatric setting (for example, in outpatient specialist practices). In cases of severe withdrawal syndrome, high risk of relapse, comorbid psychiatric disorders, or complex cases, inpatient psychiatric treatment is required (8).

Cannabinoid hyperemesis syndrome

CHS was first described 20 years ago (30). Patients present with abdominal pain and severe, cyclical vomiting (7). While the administration of standard antiemetics usually brings no relief, prolonged hot showers often improve symptoms (31).

Symptoms may be so severe that food and fluid intake becomes impossible, with patients developing electrolyte imbalances and prerenal acute kidney injury due to severe dehydration (32). Isolated cases of death have already been reported in this context (31). The Rome IV diagnostic criteria for CHS are summarized in the Table. However, the diagnosis can only be definitively established retrospectively, after complete remission of symptoms following the discontinuation of cannabis use (33). Accordingly, withdrawal under qualified supervision is the only causal treatment option, and patients should be closely monitored in either an outpatient or inpatient psychiatric setting. The most important acute measure in the emergency department is to replace fluid loss. Capsaicin cream (0.075%) applied to large areas of the trunk has an antiemetic effect. Off-label treatment with haloperidol (0.05 mg/kgBW i.m., maximum dose: 5 mg) has also been considered effective in studies (34). The use of opiates to treat abdominal pain should be avoided due to the risk of developing an addictive disorder (35).

Case Study: A 52-year-old male patient presented to the emergency department with a 3-day history of severe nausea and vomiting. After several episodes of intense vomiting 3 days earlier, he was also experiencing persistent chest pain. Since then, he had been unable to eat or drink. When asked, the patient reported that he had been smoking several joints every evening for many years. Physical examination revealed the patient to be in a reduced general condition with marked dehydration. Laboratory tests showed acute kidney failure with aninitial creatinine level of 7.77 mg/dL, a GFR of < 10 mL/min, and urea of 131 mg/dL. As an incidental finding, laboratory tests demonstrated an NSTEMI constellation with an initial troponin level of 508 ng/L. Echocardiography and computed tomography of the chest were normal. Due to the constellation seen in the laboratory results, the patient was admitted to the medical intensive care unit. Kidney function parameters and troponin levels showed an immediate decline with aggressive volume replacement. The patient could be transferred to a normal ward the following day.

Other reasons for hospital presentation

In addition to the abovementioned entities, there is a wide range of other adverse effects of cannabis that have the potential to necessitate a hospital visit. As described above, concomitant autonomic responses (for example, palpitations) can occur as part of acute intoxication. However, potentially fatal clinical pictures, such as myocardial infarction, can also be associated with cannabis use. Several studies found a significant correlation in this regard (OR = 1.72; [1.67; 1.77]; p < 0.001), although the respective patient cohorts had a high prevalence of cardiac risk factors (for example, obesity, diabetes, and tobacco use) (36).

Traffic accidents, as secondary effects of cannabis use, may also represent a relevant additional burden on emergency departments. In Canada, where the legal limit for blood THC is 2 ng/mL, the prevalence of traffic accident injuries under the influence of THC has doubled from 3.8% to 8.4% (n = 4409) (37). In Germany, a comparable limit value (serum THC of 3.5 ng/mL) has been in effect since August this year, since THC is distributed differently between the fluid and cellular components, resulting in higher serum levels compared to blood (blood/serum factor: 0.5–0.6) (38). Cannabis use combined with alcohol is not permitted, and new drivers are prohibited from using cannabis (39).

Children presenting to emergency departments following accidental ingestion of cannabis are often lethargic or comatose (20). Here again, supportive treatment should be provided. Above all, however, relevant symptoms should prompt consideration of accidental cannabis intoxication.

Conclusions for clinical practice

Acute intoxications, particularly those accompanied by anxiety attacks, are self-limiting and should be managed with supportive treatment. The use of benzodiazepines can be considered if patients are experiencing significant mental distress.

The mental health effects of chronic cannabis use are diverse and require qualified psychiatric assessment and support.

CHS is defined as severe cyclical vomiting associated with chronic cannabis use. The most important acute measure is to replace the often massive fluid loss. The only causal treatment is the cessation of cannabis use. Topical capsaicin and haloperidol have antiemetic effects.

Given that clinical manifestations are often nonspecific, it is important to consider possible cannabis use as part of the diagnostic work-up in the emergency department and investigate this in a targeted manner.

It is too early to determine whether the legalization of cannabis will achieve the German federal government’s goal of protecting users, or instead lead to increased use and a higher incidence of emergencies requiring treatment. How the situation in Germany evolves over the coming years should be monitored through appropriate empirical studies.

Conflict of interest statement
The authors declare that no conflict of interest exists.

Manuscript submitted on 15 November 2024, revised version accepted on 15 April 2025.

Translated from the original German by Christine Rye.

Corresponding author
Prof. Dr. Michael Bernhard, MHBA

Information on CME

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