Prevalence of Cannabis Use around the World: A Systematic Review and Meta-Analysis, 2000–2024
National Institute of Health Data Science, Center for Drug Abuse Prevention and Control, Peking University, Beijing, China
School of Public Health, Peking University, Beijing, China
Abstract
This study aims to perform a systematic review and meta-analysis on the global prevalence of cannabis use to inform drug prevention strategies, policy-making, and resource allocation. This study initially screened 177,843 studies published between January 1, 2000, and January 15, 2024, using peer-reviewed databases including Web of Science, PubMed, Scopus, Embase, and Cochrane Library. Ultimately, 595 studies were identified for data extraction, and 39 of these were selected as country-representative studies. Heterogeneity among the selected studies was assessed using the chi-squared test and I2 statistic, while sensitivity analysis was conducted to evaluate the robustness of the results. The prevalence of cannabis use varied between 0.42% and 43.90% across 33 European countries, 1.40% to 38.12% across 15 North and South American countries, 0.30% to 19.10% across 16 Asian countries, and 1.30% to 48.70% across 18 Oceania and African countries. The pooled prevalence of cannabis use was 12.0% [95% confidence interval (CI): 10.0, 14.3] in countries where cannabis is legalized, compared to 5.4% (95% CI: 4.3, 6.9) in non-legalized countries. Our findings indicate that the prevalence of cannabis use has disproportionately increased in most countries with the implementation of medical or recreational cannabis legalization policies and relevant geographic proximity. Increased efforts are needed to monitor newly cannabis-legalized countries and prevent initial use.
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Keywords: cannabis use, cannabis legalization, prevalence, systematic review, meta-analysis
Article notes
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Received 2024 May 9; Accepted 2024 Jun 17.
Cannabis is the most widely used drug globally, especially among adolescents, and previous research suggests that it may act as a gateway drug (1). In 2021, an estimated 219 million individuals used cannabis across nearly every country and territory (1), a 21% increase from approximately 180.6 million in 2011 (2). This rise in cannabis use raises concerns about potential adverse health effects, including impaired motor coordination, cognitive impairment, cannabis use disorders, and chronic psychotic disorders such as schizophrenia (3-4). These health issues could significantly burden global health, safety, and economic development (5). One study indicated that the incremental inpatient costs associated with cannabis comorbidity in Florida hospitals increased by 7% to 19% (6).
Studies suggest that cannabis legalization policies have significantly impacted the prevalence of cannabis use worldwide (7-8). By January 2024, more than 40 countries had implemented policies affecting global cannabis and other drug use trends (9). For instance, in the United States, the prevalence of past-month cannabis use among adolescents increased by 4.0% from 2008 to 2019 following the legalization of recreational cannabis (10).
There is a lack of comprehensive reviews addressing the recent prevalence of cannabis use worldwide, particularly from the perspective of legalization. This study conducted a systematic review and meta-analysis to estimate global cannabis use prevalence following the implementation of legalization policies, with the aim of informing drug prevention, policy-making, and resource allocation.
METHODS
Search Strategies
A systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (11), and the protocol was registered on PROSPERO (CRD42024506616). Peer-reviewed literature databases — Web of Science, PubMed, Scopus, Embase, and the Cochrane Library — were searched using a comprehensive set of search terms developed in consultation with a specialist drug librarian (Supplementary Material, available at https://weekly.chinacdc.cn/). The review focused on studies reporting the country-level prevalence of cannabis use published between January 1, 2000, and January 15, 2024.
Screening and Quality Assessment
A library was created using Endnote (version X.8, Clarivate Analytics Philadelphia, PA, USA) to catalog studies and eliminate duplicates. Initial screening of titles and abstracts was independently conducted by two authors (QW and ZQ), followed by a full-text review of the selected studies. Studies were excluded if they met any of the specified exclusion criteria (Supplementary Material).
The risk of study bias was evaluated using the Joanna Briggs Institute (JBI) Checklist for Prevalence Studies (12) (Supplementary Material). Two authors (QW and ZQ) independently rated the risk scores, classifying studies into high-risk (marked by 0–3), moderate-risk (marked by 4–6), and low-risk (marked by 7–9) groups. Any discrepancies were resolved through discussion with a third author (HZ). Only studies with moderate or low risk of bias were selected for data extraction.
Data Extraction and Representative Study Selection
Data from eligible studies were extracted into a custom-built database using Microsoft Excel (version 2019, Microsoft Corporation, Redmond, WA, USA). To account for the prevalence of cannabis use reported in multiple studies using the same database and to enhance comparability among countries, we selected representative studies for each country based on predefined selection criteria (Supplementary Material). A comprehensive search initially identified 177,843 studies, of which 101,703 were removed as duplicates. An additional 75,132 were excluded based on specific exclusion criteria, and 413 were eliminated due to high-risk bias. Consequently, 595 studies underwent data extraction, and 39 were ultimately designated as representative studies for their respective countries (Figure 1).
Statistical Analysis
The chi-squared test and I2 statistic were used to assess the heterogeneity of the selected studies (13). Random-effects models (REM) were employed due to P<0.05 or I2>50%, indicating potential heterogeneity among studies. Sensitivity analysis was conducted to evaluate the robustness of the results by systematically excluding studies with the most significant impact on the pooled outcomes. All analyses were performed using R software (version 4.3.0, R Foundation for Statistical Computing, Vienna, Austria).
RESULTS
Prevalence of Cannabis Use in Europe
Among the country-representative studies selected, the prevalence of cannabis use varied significantly, ranging from 0.42% to 43.90% across 33 European countries. The highest prevalence was observed in the Netherlands in 2013, while the lowest was reported in Sweden in 2016.
In examining the legalization of cannabis, data on prevalence has been documented by 19 countries where cannabis is legal. Typically, developed nations are among the first to relax restrictions on cannabis supply and usage penalties. For instance, in 2010, 28.14% of the Swiss population and 25.72% of the Spanish population reported using cannabis. Conversely, 14 countries reported relatively low prevalence rates of cannabis use during periods of illegality, with figures ranging from 2.76% to 30.50%. Specifically, in 2010, the prevalence was 2.76% in Macedonia, 4.31% in Romania, and in 2019, it was 6.60% in Estonia.
Prevalence of Cannabis Use in North and South America
The prevalence of cannabis use varied from 1.40% to 38.12% across 15 countries in North and South America. In the United States, an overall increasing trend was observed following the legalization of medical and recreational cannabis, with the highest prevalence of 38.12% recorded in 2021.
As in Europe, countries where cannabis is legalized often exhibit a higher prevalence rates. Data on cannabis use are available for eight countries with legalized cannabis. Both Brazil and Uruguay have shown increasing trends, with the highest prevalence reaching 23.10% in Brazil in 2019 and 20.78% in Uruguay in 2018. Additionally, eight countries reported cannabis use prevalence during periods when it was illegal, ranging from 2.60% to 18.93%. Specifically, the prevalence in Bolivia was 2.60% in 2012, in Peru it was 2.90% in 2010, and in Suriname, it was 3.90% in 2017.
Prevalence of Cannabis Use in Oceania and Africa
The prevalence of cannabis use ranged from 1.30% to 48.70% across 18 countries in Oceania and Africa. Data from three countries where cannabis is legalized reveal varying prevalence rates. In Australia, the highest recorded prevalence was 48.70% in 2004, though this has since shown a declining trend. Similarly, New Zealand saw a peak prevalence of 19.00% in 2012, which has also decreased over time. In South Africa, the prevalence was 7.80% in 2017. In contrast, fifteen countries reported lower prevalence rates, ranging from 1.30% to 10.40%, during periods when cannabis was illegal. Specifically, in 2017, Benin had a prevalence of 1.30%, while Tanzania reported a prevalence of 2.30%.
Prevalence of Cannabis Use in Asia
The prevalence of cannabis use in 16 Asian countries ranged from 0.30% to 19.10%, which is relatively lower compared to European and American countries. Two countries specifically documented this data. In Israel, cannabis use prevalence increased from 5.43% in 2010 to 19.10% in 2017. In Lebanon, it was 1.60% in 2017. Fourteen countries reported cannabis use prevalence during periods when it was illegal, with rates ranging from 0.30% to 6.00%. In 2004, Japan had the lowest prevalence at 0.30%. The prevalence was 0.60% in Laos in 2015 and in Vietnam in 2013.
Meta-Analysis
In the meta-analysis, 33 studies reported the prevalence of cannabis use in 32 countries where cannabis is legalized, involving 17.12 million samples with 1.26 million cases. Conversely, 11 studies reported the prevalence in 51 countries where cannabis is illegal, involving 1.28 million samples with 205,630 cases. Overall, countries with legalized cannabis showed a higher pooled prevalence of use compared to those with illegal cannabis. The REM estimated the pooled prevalence of cannabis use to be 12.0% [95% confidence interval (CI): 10.0, 14.3] in legalized countries, compared to 5.4% (95% CI: 4.3, 6.9) in non-legalized countries (Figures 2 and 3). Sensitivity analysis revealed no significant variations, confirming the stability of the results. However, the high heterogeneity observed in the analysis and potential publication bias in some studies could be attributed to the diversity of countries and the varying periods from which data were sourced.
DISCUSSION
Our findings indicate a disproportionate global increase in cannabis use, with significant regional variations since 2000, consistent with previous studies. This rise may be attributed to increased access to cannabis, shifting cultural perceptions, and evolving legislation (14). Worldwide, more countries are decriminalizing cannabis, and in those with existing legalization, regulations are becoming more permissive (e.g., recreational use and possession limits) (15). The acceleration of economic globalization presents additional challenges to decreasing the prevalence of cannabis use.
Notably, countries with medical or recreational cannabis legalization policies have shown an increasing trend and higher prevalence of cannabis use. In Japan, where cannabis control is relatively strict, the prevalence remains low (16). In contrast, in the United States, cannabis use has increased following the legalization of recreational cannabis in Colorado and Washington in 2012 (17).
The prevalence of cannabis use demonstrated regional consistency, with neighboring countries or continents exhibiting similar levels of use. For example, in Europe, countries like the Netherlands and Spain showed relatively high cannabis use prevalence (18). This trend also extended to nearby countries, such as France and Germany, where cannabis use was similarly common (19).
The study is subject to some limitations. First, the study utilizes peer-reviewed literature databases, which include many studies with non-continuous data. Second, it is restricted to studies published in English, potentially excluding valuable research in other languages. Third, publication bias regarding cannabis use was not accounted for due to variations across countries. Lastly, the analysis did not examine detailed regulations of cannabis legalization; future studies should investigate the effects of various cannabis legalization measures.
Our findings indicated that the prevalence of cannabis use has disproportionately increased in many countries following the implementation of medical or recreational cannabis legalization policies, particularly in regions geographically close to these areas. As a gateway drug, this trend may lead to an increase in both cannabis use and overall drug use. Therefore, enhanced monitoring of newly cannabis-legalized countries and efforts to prevent initial use are necessary.
Conflicts of interest
No conflicts of interest.
SUPPLEMENTARY DATA
Funding Statement
Supported by the National Natural Science Foundation of China [72174004, 91546203]
References
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