Introduction
Disorders caused by drug use represent a considerable burden for individuals and society1. The World Drug Report states that between 2010 and 2022, the number of people who use drugs increased by 23%. Problems caused by drugs and dependence on them are preventable and treatable. With more than 209 million users, representing 4% of the world’s population, cannabis is the most widely used illegal drug worldwide2. Thirteen million people have developed dependence, and among users of psychoactive substances, after alcohol, it is the most frequent reason for seeking treatment3,4.
In the United States of America, the proportion of young adults who reported cannabis consumption in 2021 reached 43%, a significant increase from 29% in 2011. Consumption in the past month was reported by 29% of young adults in 2021, compared with 17% in 2011. Daily consumption also increased significantly duringthis period, reported by 11% of young adults compared with 6% previously5.
In Mexico, according to data from the National Survey on Drug, Alcohol and Tobacco Consumption 2016-2017, cannabis remains the illegal substance with the highest consumption among the adult population, with a prevalence of 12.8%, representing a historic increase of 4.8% compared with 20086, and is comparable to the trend observed in other countries7.
The main cannabinoids with psychoactive properties, namely, tetrahydrocannabinol (THC) with its isomers and stereochemical variants, are included in Schedule I of the Convention on Psychotropic Substances for having the capacity to produce a state of dependence and to constitute a public and social problem. Article 4, paragraph (c), of the 1961 Convention, as amended, limits the use of cannabis to medical and scientific purposes. According to the Convention, cannabinoids can be evaluated in controlled clinical trials to assess the benefits and harms of their use in medicine. The legalization of non-medical use is an evident violation of the Conventions and cannot be considered covered by flexibility, since such instances do not allow any exception to the limitation in question8,9. Recently, the United Nations Commission on Narcotic Drugs recognized the medical potential of cannabis, but only for the use of purified derivatives with pharmaceutical quality and standard medical-grade evidence of efficacy and safety; this does not apply to smoking cannabis, cannabis concentrates, or artisanal derivatives10.
It is of considerable concern that the concentration of the most powerful psychoactive component of cannabis, THC, has been progressively increasing. The World Report11 states that in the last 20 years, the potency of cannabis products has nearly quadrupled in the United States of America. The percentage of Δ9-THC increased from approximately 4% in 1995 to 16% in 2019. However, the percentage of adolescents who perceive cannabis as harmful has decreased by 40% during the same period, and a lower perception of the risks associated with drug use has been related to an increase in consumption rates.
Given this view, it is expected that increasing its availability and losing its illegal status will lead to an increase in its use12, both exploratory and permanent.
Best public health practices should guide how to regulate cannabis effectively and minimize negative health impacts. That is, regulation should prioritize public health over other objectives, including industry profits, state tax revenues, and business development, which while valid bases for government action in general, can lead to harmful outcomes in the regulation of potentially harmful substances13. The public health approach should learn from the successes and failures of national and international regulatory frameworks for cannabis and other substances, especially tobacco. Valuable lessons can be taken from the history of tobacco control and legislation; it is documented that the tobacco industry designed its product to be increasingly addictive and issued misleading messages, creating variants supposedly promoted as reduced risk that ultimately were not14,15.
Due to tobacco industry interference with public health policies, the World Health Organization (WHO) Framework Convention on Tobacco Control includes Article 5.3, which urges governments to take measures to exclude the tobacco industry from policymaking16. It is especially concerning that the tobacco industry shows interest in the cannabis and electronic cigarette business, as these are also being used to inhale THC from high-concentration liquids, which increase the risk of addiction and toxicity17,18. Given the danger that tobacco companies may enter the cannabis market, their acquisition of shares in the cannabis business has been prohibited in the United States of America19.
Although existing literature may be limited in answering how legalization and regulation will affect cannabis use and associated outcomes, it does offer significant information on how we should evaluate the effects of changes in public policy.
This narrative review aims to describe tools for legislation that protect public health in relation to cannabis, reviewing the health effects of its consumption and the impact of changes in global policy.
Method
The recommendations of the Cochrane Group for Rapid Reviews20 were followed. An exhaustive search on cannabis and its legislation was conducted from October 2021 to February 2024, using material available in English and Spanish in the PubMed, MEDLINE, Embase, PsycINFO, and CENTRAL (Cochrane Controlled Register of Trials) databases, governmental websites, and databases from Public Health Departments and the International Narcotics Control Board (INCB). The following terms were used for the search: [marijuana OR cannabis], [legalization OR public health OR policy], and [problematic use OR risky use OR health]. Other potentially relevant studies were searched by screening reference lists and citations of included studies. All authors reviewed and analyzed them using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system and discussed the articles to provide recommendations. We present the following article according to the narrative review reporting checklist21.
Health effects
Cannabis has immediate harmful effects when under the influence of its components when smoked, which is the most common route, and additionally can manifest negative health effects in the medium and long term22.
Acute harmful effects
During acute cannabis intoxication, people may exhibit rapid deterioration in attention and reaction time23. These effects can affect the ability to drive automobiles and machinery, causing traffic and workplace accidents24. Episodic consumption also increases the frequency of coronary events and the risk of cardiovascular diseases in young subjects, who generally have a low baseline risk25.
During this intoxication, there may be psychotic responses. Daily cannabis consumption has been associated with an increased risk of psychotic disorder compared to people who had never consumed it (odds ratio [OR]: 3.2; 95% confidence interval [95% CI]: 2.2-4.1), especially for daily usage of high-potency cannabis (OR: 4.8; 95% CI: 2.5-6.3)26. Heavy cannabis consumption increases the risk of psychotic states in a dose-response relationship27. Emergency department visits in the United States of America for cannabis intoxications have been progressively increasing in parallel with the increase in THC concentration in cannabis leaves28.
Chronic harmful effects, medium and long term
Cannabis consumption can be problematic in at least one-third of users, a condition called “cannabis use disorder.” Cannabis withdrawal syndrome has also been documented, which includes alterations in mood, increased perceived stress, and irritability29,30 These disorders are more common in subjects who consumed habitually or significantly during adolescence, appearing more frequently than in those who started consumption as adults, so it has been suggested that the initiation of use should not be permitted until age 2430,31.
People with cannabis addiction have an increased risk of serious problems in attention, memory, and learning32. In addition to acute emotional disorders related to withdrawal, such as irritability and anxiety33, prolonged cannabis consumption is associated with affective dysregulation. A systematic review found an association between cannabis consumption in adolescence and the risk of developing depression (OR: 1.37; 95% CI: 1.16-1.62; I2: 0%), suicidal ideation (OR: 1.50; 95% CI: 1.11-2.03; I2: 0%), and suicide attempt (OR: 3.46; 95% CI: 1.53-7.84; I2: 61.3%). The high prevalence of adolescents who consume cannabis could generate a large number of young people who develop depression and suicidal tendencies related to this consumption34.
Respiratory effects
Cannabis smoke, a product of plant combustion, is very similar in composition to tobacco, if we leave aside the addictive alkaloids specific to each and the possible flavorings, substances added to manufactured cigarettes, and chemicals used in cultivation. Cannabis smokers have reported more susceptibility to respiratory infections, wheezing, difficulty breathing, altered pulmonary function tests, cough, phlegm production, bronchodilation, and other respiratory symptoms35. These symptoms are explained by irritation of the airways and lungs, which affects mucociliary movement, an important defense against respiratory infections.
A case-control study identified that cannabis smokers presented more severe chronic respiratory symptoms, including wheezing, difficulty breathing, altered pulmonary function tests, cough, phlegm production, and bronchodilation36. It has also been described that they can develop bullous lung disease with a higher incidence of tension pneumothorax than tobacco smokers and non-smokers, experiencing prolonged postoperative stays and a higher incidence of pneumothorax recurrence after the operation. The risk of chronic respiratory symptoms and bullous lung disease in cannabis smokers has been reported to be dose-related37–40.
Despite this, several known effects of tobacco have been difficult to demonstrate in pure cannabis users, and clarifying cannabis’s role is complicated by the fact that many people consume both cannabis and tobacco. While cannabis is capable of producing chronic bronchitis and changes in bronchial lining cells similar to those observed in tobacco smokers, it has been difficult to demonstrate chronic obstructive pulmonary disease, emphysema, and accelerated decline in lung function in cannabis users who do not smoke tobacco35,41.
Smoking cannabis does not help treat asthma, as disseminated in many pro-cannabis forums; on the contrary, it can worsen cases and exacerbate crises35, despite Δ9-THC having bronchodilator properties.
Prolonged cannabis consumption may increase the risk of testicular cancer, but in general, the relationship between cannabis use and the development of certain types of cancer remains unclear42,43, which is striking because cannabis smoke contains known carcinogens. Lung cancer has not been consistently associated with pure cannabis users, but its frequent combination with tobacco (whether simultaneous or sequential) makes cannabis users a high-risk group.
Results of cannabis legislation policy in various countries
Legislation has progressed more rapidly than the acquisition of knowledge about its risks, especially at the population level. In fact, several national legislation proposals have been developed without taking advantage of experience in cannabis regulation or legalization in other countries. Table 1 lists the main considerations, foundations, and results obtained after cannabis legislation for recreational use in various countries.
Table 1. Main points of international cannabis legislation (legalization and regulation)
| Country (year) | Considerations and foundations | Results obtained |
|---|---|---|
| Netherlands (1976)44,45 | – The policy objective is to reduce drug demand, drug supply, and risks to users, those around them, and society – In 1990, coffee shops authorized to sell and consume cannabis in quantities of no more than 5 g per person per day were created, strictly regulated; they control the quantity and conditions under which they are sold and consumed, without advertising drugs – Minors under 18 years old do not have access to coffee shops or purchases |
– These establishments have given rise to the sale of other drugs and increased sale of designer drugs – Low rates of human immunodeficiency virus among people who use drugs and comparatively low cannabis consumption among young people – Fewer arrests for minor drug-related offenses – Increase in illicit substance trafficking in the past year 45 |
| USA (1996) Private sector participation46 |
– Recreational use (2012) legal, modeled on alcohol regulations – Medical use (1996); in some states consumption is permitted for medical use, including products with regulated THC concentrations47 |
– In Washington, perceived risk of cannabis consumption in adolescents decreased and consumption increased after legalization of recreational use48,49; lower perception of harm risk with its use in adolescents52 – Emergence of risks from unintentional cannabis exposure in children50 – Legalization of recreational cannabis in the USA was associated with a 15% increase in fatal motor vehicle collisions and a 16% relative increase in associated deaths, without conclusive differences between the first year and subsequent years after legalization51 – The findings reported in the World Drug Report (2022)11 indicate: general increase in cannabis consumption with a reduction in the gender gap; increase in the proportion of people with psychiatric disorders associated with regular cannabis consumption and in consumption among pregnant women even before, during, and after pregnancy, compared to those in states that have not legalized it – A “simultaneous quadruple confluence” of increased prevalence of use, increased intensity (frequency and quantities) of use, increased THC content of cannabis products, and increased hospitalizations for acute intoxications or cannabis use disorders – So far, legalization has not displaced illegal markets; it remains attractive for different reasons, including price, quality, and accessibility |
| Uruguay (2013) Greater state control53 |
– Includes recreational use – Central state commission with sales monopoly and control of production, packaging, distribution, sale, promotion, and profit distribution – Government authorities have declared that Uruguay’s capacity for monitoring systems of public health impact is very limited – Home plant cultivation authorized, as well as clubs where members can acquire cannabis – Sale only in approved places, or commission sales points, with defined locations and characteristics, and health messages; they can sell in pharmacies in packages with content and without promotion (neutral) – Maximum weekly sale of 10 g per person – Marked THC content, with preferential prices for low THC, less addictive – Driving under the influence of cannabis is prohibited; the limit for driving under the influence of cannabis has been set at a serum THC level of 10 ng/ml |
– Consumption among adolescents increased between 2009 and 2018, being the group most impacted by legalization54 – Thanks to market restrictions imposed by the state monopoly, THC content and the range of cannabis products have remained stable8 – An association is reported with an immediate 52.4% increase (95% CI: 11.6-93.3; p = 0.012) in the fatality rate of light vehicle drivers; however, no significant change was observed in the mortality rate of motorcyclists. In Montevideo, legislation was associated with an absolute increase in the mortality rate of light motor vehicle drivers by 0.06 (95% CI: 0.01-0.11; p = 0.025), but no significant associations were observed in rural settings55 – The illegal market continues; it is estimated that only half of the cannabis consumed in the country is of legal origin |
| Canada (2018)56 | – Legalization and regulation of the use, production, and sale of cannabis for non-medical purposes – Minimum age for consumption and legal purchase: 18 years in Alberta, 21 years in Quebec, and 19 years in all other provinces – Restrict places of use and prohibit advertising – Regulate the legal availability of a variety of commercially produced cannabis products through retail systems – Define provisions for limited home cultivation and a personal possession limit (30 g) of cannabis in most provinces – Driving vehicles under the influence of cannabis is prohibited based on defined limits – Provisions vary for each province |
– Legalization was associated with a 26% increase in the prevalence of current cannabis consumption, with confidence intervals of 23.1% to 29.1% (p = 0.01)57 – According to the World Drug Report (2022)11, there has been an increase in consultations for mental disorders associated with consumption; there has been a clear diversification of cannabis products, with very potent products such as concentrates and edibles entering the market after legalization, and the average THC level in cannabis has increased after legalization – Coexistence of the illegal cannabis market |
| Luxembourg (2021)58 |
– Legalization and regulated use for recreational purposes – Public possessions no greater than 3 g – Sale of seeds and derived products is regulated by the state – Cultivation is permitted for people over 18 years of age for personal consumption, no more than four plants inside their home – Retail sale and commercialization are prohibited |
– Increase in market dispute by Canadian companies – Recent legislation, with pending evaluation of short, medium, and long-term impact |
| Malta (2021)59 | – Legalization for recreational purposes – It is legal to carry up to 7 g of cannabis – It is legal to establish cannabis associations – Crops between 7 g per day and 50 g per month – It is prohibited to smoke cannabis in public – Each household can grow four plants – Only for those over 21 years old |
– Recent legislation, with pending evaluation of short, medium, and long-term impact |
95% CI: 95% confidence interval; THC: tetrahydrocannabinol.
Evaluating the changes caused by legalization, regulation, and decriminalization of cannabis use has been a challenge, due in part to heterogeneity in the forms and principles on which evaluation by various involved entities is based.
Many of the public health impacts related to cannabis legalization, including increases in its consumption, occurred initially in Canada and the states of Washington and Colorado, prior to the issuance of laws that allowed the existence of a legal industry that produced, promoted, and sold cannabis products, because in these places the commercialization of smoked cannabis as medicine was permitted. The promotion of smoked cannabis as medicine led to an explosion in the number of patients who consumed it, in addition to normalizing its consumption and, therefore, increasing consumption prevalence and related health consequences.
Both the WHO and the INCB have insisted that smoked cannabis should not be prescribed as medicine. If necessary, and after appropriate clinical trials and fulfilling regulatory requirements requested of any new medication, standardized medications regulated by government public health and health risk agencies should be prescribed, which may contain cannabinoids such as cannabidiol or THC1–3.
Considerations for health protection
Given limited information, the best procedure is to prioritize protection and exercise caution. We present legislative versions with experiences in the Netherlands, the United States of America, Uruguay, Canada, Luxembourg, and Malta44–59, which include and integrate best public health practices and can be considered at a minimum level:
– Make maximum use of available information and experience from various existing legislations (Table 1). While acquiring one’s own information is required, many of the consequences of a legislative scheme can be learned from experiences in other countries and can be contrasted with the strength of institutions in countries that are close to regulating commercialization.
– Above all, marketing aimed at increasing sales must be prohibited, and efforts must be made to prevent the participation of the powerful tobacco and alcohol industries to the greatest extent possible.
– A cannabis legislation model should consider the cost-effective measures included in the WHO Framework Convention on Tobacco Control16, known as MPOWER (Monitor, Protect, Offer, Warn, Enforce and Raise taxes):
Monitor cannabis use, its effect on comprehensive health, and monitoring of compliance with control policies.
Protect from exposure by completely prohibiting promotion of its use, advertising, promotion, and sponsorship, which would ensure that public health interests are prioritized over commercial ones.
Offer evidence-based treatments for cessation, which requires developing care centers with trained professionals before any legislation.
Warn about health risks on packaging, and ensure it is neutral to avoid making it attractive and incentivizing consumption, including detailed description of content and its risks.
Enforce by applying taxes to cannabis products to have a disincentive effect, especially on adolescents, with the plan that they are progressively updated. In the case of tobacco, this measure has immediate effects and provides economic resources that can be applied to prevention or addiction treatment.
Raise taxes: Protect the population from secondhand cannabis smoke; it is important to avoid its use in public and especially to prohibit smoking cannabis in places where smoking tobacco is prohibited.
– Establish measures to prevent traffic and workplace accidents derived from acute intoxication from cannabis consumption. A program such as “Drive without alcohol” should be expanded to “Drive without alcohol and without cannabis” to identify individuals who exhibit impairments in attention and reaction times through a sensorimotor skills test, corroborated by a THC detection test in saliva that detects recent use, in addition to behavioral tests of psychomotor performance.
– Ensure that access to cannabis and its products is restricted to those over 24 years of age, with auditable and verifiable measures, such as obtaining a copy or photo of an identity document and verifying age in establishments with a health license. This implies incorporating all procedures that have been implemented in other regions, as well as clearly establishing which will be the competent bodies for commercialization oversight and attributing powers to them that improve law enforcement.
– Develop and strengthen prevention and intervention programs aimed primarily at adolescents, but also at adults. These programs should generate comprehensive family prevention actions with training for parents, children, and the family collectively. Allocate budget to programs that promote the acquisition of social skills such as social influence approaches, budget for prevention campaigns in mass media, health centers, schools, and workplaces. Also create preventive programs focused on the adult population, highlighting the risks associated with substance use and addressing the low perception of risk. Evidence- based preventive interventions need to encompass the entire prevention chain, from universal and selective prevention to indicated prevention. Promoting education about “safer” routes of cannabis administration will become critical, and it will be essential to control cannabis-related deterioration and reduction in use.
– Consider education about the potential risks of mixing cannabis with alcohol or other drugs, as their effects could be drastically intensified.
– Establish public policy reinforcement mechanisms to optimize treatment, rehabilitation, and social reintegration of people with problematic use of psychoactive cannabis, without subjecting them to criminalization or discrimination for any reason. Treatments should be free and universally accessible, and should contemplate attention to vulnerable populations, multiculturalism, gender issues, and age.
– Raise awareness among health professionals about the health risks associated with cannabis consumption and train them to provide brief advice and treatment.
– Limit the potency of cannabis products. The THC content of cannabis plants and derived products, including vaping liquids, must be identified and limits must be placed on the permitted concentration, in order to reduce the risk of addiction and acute intoxication. For example, in the United Kingdom, a concentration exceeding 2 ng/mL is considered to represent a driving risk. The increase in THC concentration makes the product more addictive and produces more acute intoxications that include psychotic-type reactions.
– An additional way to discourage the use of THC, especially at high concentrations, is to establish a tax rate that increases proportionally to the THC concentration of plants and vaping liquids (which currently have a prohibition legislative framework).
Conclusions
Cannabis has been the most widely used illicit drug worldwide, making it essential to educate the public about the consequences associated with its use. It is by no means an innocuous and risk-free substance, as is sometimes suggested. Chronic use leads to addiction and carries the risk of developing mental disorders such as depression and schizophrenia, and if smoked, entails the risk of lung damage. Regulations governing its sale and acquisition must be carefully elaborated.
A policy that includes a centralized state commission with monopoly may be advantageous, since in countries where this was adopted, no significant increase in consumption has been observed. Likewise, it is important to monitor, control, and warn about the concentrations of psychotropic compounds in cannabis-derived products. The MPOWER model for tobacco control can be incorporated into cannabis legislation that prioritizes public health and population well-being. It is essential to be clear about the results that have been obtained with different legislations in other countries to avoid the risk of fostering addiction and increasing healthcare expenses in both the short and long term.
Funding
No funding was received.
Conflicts of interest
The authors declare they have no conflicts of interest.
Ethical considerations
Protection of people and animals. The authors declare that no experiments were conducted on humans or animals for this research.
Confidentiality, informed consent, and ethical approval. The study does not involve personal patient data or require ethical approval. SAGER guidelines do not apply.
Declaration on the use of artificial intelligence. The authors declare that they did not use any type of generative artificial intelligence for the writing of this manuscript.
