Abstract
Background
The federal government of Germany is planning to liberalize the recreational cannabis market for adults. We aimed to collect key baseline data on frequency of use, routes of administration, and co-use of cannabis and inhaled nicotine or tobacco products in the population.
Methods
Based on data from a national survey of 9644 people aged >14 years, we analyzed self-reported use of cannabis in the past 12 months and preferred route of administration (single choice: smoked with tobacco; smoked without tobacco; inhaled without tobacco; consumed with food; consumed in another form).
Results
The prevalence of past-year cannabis use was 4.6% (95% CI [4,2; 5,1%]), with higher rates among 14–24– (11.4%) and 25–39-year-olds (8.2%) as well as among co-users of inhaled nicotine or tobacco products, particularly waterpipe users (27.0%). Smoking cannabis with or without tobacco was the preferred route of administration, reported by 92.4% (95% CI [89,6; 94,6%]). It was most frequently reported by 14–24-year-olds and by co-users of inhaled nicotine or tobacco products.
Conclusion
Smoking remains the predominant form of using cannabis—especially among younger users, who are at greatest risk of cannabis-related consequences. The true prevalence of cannabis use may have been underestimated in our study, however, as not all participants answered the questions on cannabis. Nevertheless, preventive and harm reduction efforts are needed to reduce the harm from using cannabis. Continuous monitoring is required to evaluate the effects of the forthcoming law changes in Germany.
Cannabis is one of the most frequently used psychoactive drugs worldwide. In the European Union its use has increased during the past decade, and in 2019 approximately 4% of persons aged 15 to 64 had used cannabis in the past month (1). Germany has seen the same trend in recent years (2). The current 12-month prevalence of usage is estimated at 8% in 12- to 17-year-olds, 25% in 18- to 25-year-olds, and 9% in 18- to 64-year-olds (3, 4).
Following the legalization of cannabis for medical purposes in 2017, the German federal government elected in 2021 announced its intention to legalize cannabis for recreational use by adults (5). Based on the plans disclosed in April 2023 and approval of a draft bill by the Federal Cabinet on 16 August 2023, cannabis possession and home cultivation could be legalized early in 2024 (6). As complete legalization, including a regulated commercial market, would be in contravention of EU laws, the German government has announced that licensed sales will be allowed as part of scientific pilot projects in selected regions in the near future.
There is substantial evidence that cannabis use is associated with health risks, including impaired respiratory function, motor vehicle accidents, and the development of psychoses among frequent users (7, 8). In adolescence particularly, regular cannabis use most probably has adverse effects on cognition, psychosocial development, and mental health, and increases the risks of poor school performance and leaving school early (8–11). On the other hand, there is growing evidence that cannabis can have moderate therapeutic benefits if used for medicinal purposes, e.g., in patients with chronic neuropathic pain and with regard to tics in patients with Gilles de la Tourette syndrome (12–14).
One important aspect of cannabis use with regard to the associated health risks is its route of administration. Common routes of cannabis administration involve smoking (e.g., in joints or waterpipes), ingestion (e.g., edibles in food and drinks), vaping (e.g., vaping of dry cannabis plant material with vaporizers or vaping of cannabinoid-infused liquids with e-cigarettes), and dabbing (i.e., quick inhalation of high-potency cannabis concentrate with a heated metal element) (15–19). The different routes of administration are likely to have different adverse health effects, and inhalation of cannabis with tobacco smoke is probably the most harmful form of consumption, in particular with regard to respiratory function and the development and persistence of cannabis use disorders (18, 20–22). For Germany, data collected in 2014 for the Global Drugs Survey suggest that smoking with tobacco was the most common way to use cannabis (in 87% of the cannabis users who had used cannabis in the previous 12 months [past-year cannabis users]) (23). More recent data on preferences of administration routes are lacking but are key to assessing the risks and developing harm reduction strategies.
For the planned changes to the laws affecting cannabis in Germany, information on the prevalence of cannabis use, associated user characteristics (e.g., age and co-use of nicotine and tobacco products), and users’ preferred routes of administration constitute key baseline data. We therefore formulated the following research questions:
What is the current 12-month prevalence of cannabis use in the general population of Germany aged 14 years and older ?
How does the 12-month prevalence of cannabis use vary according to relevant characteristics of the persons concerned?
What is the predominant form of cannabis consumption in the subgroup of past-year users?
How does the predominant form of cannabis consumption vary in the subgroup of past-year users according to relevant sociodemographic and smoking characteristics of the persons concerned?
Methods
We conducted a cross-sectional analysis using data from the German Study on Tobacco Use (DEBRA) (24). An extended version of the methods of this study is available in the eMethods. In brief, DEBRA collects data every other month by means of computer-assisted face-to-face household interviews in a sample of approximately 2000 persons aged 14 or older. Respondents are selected by random stratified sampling (50%) and quota sampling (50%; details: https://osf.io/e2nqr/). The study was approved by the medical ethics committee of the Heinrich Heine University Düsseldorf (HHU 5386R). For the current analysis we included data from waves 36 to 40 (April/May 2022 to January/February 2023). A detailed analysis plan was registered prior to data evaluation (https://osf.io/zy8sw).
E-Methods.
Methods
The DEBRA study was approved by the ethics committee of Heinrich Heine University Düsseldorf (ID 5386/R) and registered in the German Registry of Clinical Studies (DRKS00011322, DRKS00017157, DRKS00028054). A detailed account of the overall study methods has been published in a study protocol (24). The study comprises an ongoing nationwide, computer-based, face-to-face household survey of persons aged 14 years and over. Starting in 2016, every 2 months a new representative sample of about 2000 persons is interviewed as part of a multi-topic survey (six waves with a total of about 12 000 interviews each year).
Initially the interviewees were selected using a multilevel, multistage random sampling technique. In this process, all communities in Germany are sorted by federal state, district, and community type. Germany is divided into 53 000 small geographic areas to determine the primary sampling units. For each of these small areas the sample size is determined by the ratio of the total number of households in the area to the total number of households overall. The secondary sampling units are represented by private households and selected by means of a random walk process. The tertiary sampling units are the target persons themselves and are chosen at random (using the Kish selection grid [”Schwedenschlüssel”]).
Since January 2020 (DEBRA wave 22), the target persons have been selected in a dual-frame process—a combination of random and quota sampling. This design modification has been described in greater detail elsewhere (www.osf.io/e2nqr/). This sample provides responses to general sociodemographic and socioeconomic questions as well as questions on use of tobacco products and alternative nicotine-release systems. For the purposes of the present article, we analyzed data from waves 36 to 40 (April/May 2022 to January/February 2023), to which questions on cannabis (listed below) had been added.
Measurement of cannabis use
The topic of cannabis was prefaced with the following statement: “The following questions relate to cannabis, also known as marijuana or hashish. The federal government is planning to legalize these products. Commercially available products containing cannabidiol (CBD), which has no intoxicating effect, are not included in the scope of the questions. Please be aware that your responses are analyzed anonymously and in summarized form, so that you cannot be identified. All data will be passed to the Institute for General Practice at the University of Düsseldorf and used exclusively for purposes of research. Are you willing to answer two questions on this subject?”
Persons who agreed to answer questions related to cannabis were then presented with the following questions:
“Have you ever used cannabis?”
Yes, I have used cannabis every day or almost every day during the past 12 months.
Yes, I have used cannabis at least once each week during the past 12 months.
Yes, I have used cannabis at least once each month during the past 12 months.
Yes, I have used cannabis during the past 12 months, but less often than once each month.
Yes, I have used cannabis, but not in the past 12 months.
No, I have never used cannabis.
No response
“How do you predominantly use cannabis?”
I predominantly smoke cannabis with tobacco, e.g., in joints or pipes.
I predominantly smoke cannabis without tobacco, e.g., in joints or pipes.
I predominantly inhale cannabis without tobacco, e.g., in e-cigarettes or vaporizers.
I predominantly consume cannabis together with food.
I predominantly consume cannabis in a different form.
No response
Supplementary notes on the statistical methods
A comprehensive statistical analysis plan was designed prior to evaluation of the data and published: see www.osf.io/zy8sw.
For analysis of the first two research questions, the data were weighted. The data basis for the weighting procedure is distribution of households according to the most recent microcensus in Germany. Together with the design weighting at household level, this weighting smooths out the loss of the gross sample and assigns a higher factor to persons who are seldom at home, as they are less likely to be selected. Next, the sample of households is transformed into a sample of persons. Finally, age, sex, region, and other demographic characteristics are adjusted at person level. Details of weighting can be found in the study protocol (24). The data were not weighted for analysis of the third and fourth research questions, because the analyses relate to a specific subgroup whose true distribution parameters with regard to sociodemographic and socioeconomic characteristics are unknown.
As explained, persons could refuse to answer the questions about cannabis. Selection bias may therefore exist in that persons who opt out of these questions are more likely to be cannabis users. For this reason we conducted a post-hoc sensitivity analysis, assuming that 50% of persons who declined to respond had used cannabis in the previous 12 months and the other 50% had not (the rate of 50% was arbitrary). Allocation to the two groups was random. The prevalence of cannabis use in the previous 12 months was then recalculated.
Measurements
Respondents were explicitly asked to opt in to answering questions on cannabis use.
Frequency of cannabis use was measured by asking: “Have you ever consumed cannabis?” Response options: “Yes, I have consumed cannabis in the past 12 months (1) …daily or almost daily; (2) …at least once a week; (3) …at least once a month; (4) …, less often than once a month; (5) Yes, I have consumed cannabis, but not in the past 12 months; (6) No, I have never consumed cannabis; (7) No response.” Responses 1 to 4 indicated past-year cannabis use.
The route of cannabis administration in past-year users was measured by asking: “How do you consume cannabis mostly?” Response options: “I mostly (1) …smoke cannabis with tobacco, e.g., in joints or pipes; (2) …smoke cannabis without tobacco, e.g., in joints or pipes; (3) …inhale cannabis without tobacco, e.g., in e-cigarettes or vaporizers; (4) …consume cannabis together with food; (5) …consume cannabis in a different form; (6) No response.”
We measured the following characteristics: age in years; sex; educational attainment; monthly net household income per person; migration background; federal states cluster; and region of residence.
Furthermore, we measured the co-use of the following inhaled nicotine and tobacco products: tobacco cigarettes; e-cigarettes; heated tobacco products; and waterpipes.
Statistical analyses
As part of a non-response analysis, we compared the above-mentioned characteristics and co-use between the respondents who answered the cannabis-related questions and those who did not.
We used weighted data to address our first and second research questions. The weighting accounts for personal and household characteristics (age, sex, household size, educational attainment, and region), in order to achieve representativeness for the population of Germany. Details can be found in the general study protocol (24) and elsewhere (https://osf.io/s2wxc). For our third and fourth research questions, we used unweighted data.
Results
A total of 10 484 persons were interviewed, of whom 9644 (92.0%) opted in to answer the questions on cannabis and 840 (8.0%) opted out. Opting out was more likely in the age group 25–39 years (10.9%), in persons with low educational attainment (10.7%) and low income (9.7%), and in persons living in a rural region (10.2%) and in southwestern Germany (9.6%). The eTable shows the characteristics of the respondents.
eTable. Characteristics of the total sample (unweighted n = 9644).
| Characteristics | N (%) |
|
Age in years 14–24 25–39 40–64 65+ |
931 (9.7) 1977 (20.5) 4115 (42.7) 2621 (27.2) |
|
Sex Male Female |
4607 (47.8) 5034 (52.2) |
|
Educational attainment*1 Low Middle High |
2765 (28.7) 3690 (38.3) 2917 (30.2) |
|
Income*2 Low (< €1000) Middle (€1000–2333) High (> €2333) |
2457 (25.5) 4839 (50.2) 2328 (24.1) |
|
Migration background Yes (one or both parents born abroad) No |
1337 (13.9) 8109 (84.1) |
|
Region of residence*3 Rural (< 20 000 inhabitants) Urban (20 000–500 000 inhabitants) Metropolitan (> 500 000 inhabitants) |
3751 (38.9) 4059 (42.1) 1834 (19.0) |
|
Federal states cluster*4 Northwest Northeast Southwest Southeast |
3687 (38.2) 1325 (13.7) 4028 (41.8) 604 (6.3) |
|
Use of tobacco Current Former Never |
3 538 (36.7) 1 564 (16.2) 4 522 (46.9) |
|
Use of e-cigarettes Current Former Never |
188 (1.9) 1159 (12.0) 8277 (85.8) |
|
Use of heated tobacco products Ever (current or former) Never |
581 (6.0) 9048 (93.8) |
|
Use of waterpipes Current Former Never |
195 (2.0) 1646 (17.1) 7795 (80.8) |
Percentages are presented within the total group. Percentages do not add up to 100% due to missing data.
*1 Low, no qualification or junior high school equivalent; middle, secondary school equivalent (year 10); high, university entrance qualification or advanced technical college equivalent
*2 Details: https://osf.io/387fg
*3 Details: https://osf.io/zp7c6
*4 Northwest: Bremen, Hamburg, Lower Saxony, North Rhine–Westphalia, Schleswig–Holstein; northeast: Berlin, Brandenburg, Mecklenburg–Western Pomerania, Saxony–Anhalt; southwest: Baden–Württemberg, Bavaria, Hesse, Rhineland–Palatinate, Saarland; southeast: Saxony, Thuringia (a clustering similar to a previous study [36])
The prevalence of past-year cannabis use was 4.6% (weighted; 448/9666; [95% confidence interval 4.2; 5.1%]). The prevalences were 0.7% [0.5; 0.9%] for daily or almost daily use; 0.8% [0.7; 1.0%] for use at least once a week; 0.7% [0.6; 0.9%] for use at least once a month; and 2.4% [2.1; 2.7%] for use less often than once a month (hence, past-month use was 2.2% [1.9; 2.5%]). The rate of previous use of cannabis but not in the past 12 months was 13.0% [12.3; 13.7%] and that of never use was 82.2% [81.4; 83.0%]. The remaining 0.2% did not respond. In a post-hoc sensitivity analysis (for details, see the eMethods), we hypothetically assumed that a randomly selected 50% of the 840 persons opting out were past-year cannabis users, resulting in an overall prevalence of 8.4% (weighted: 879/10 484).
Table 1 shows rates of past-year cannabis use by sample characteristics. Rates markedly above average were observed in age groups 14–24 years (11.4%) and 25–39 years (8.2%); among persons living in metropolitan areas (8.2%); and among co-users: 10.2% among current tobacco users, 13.3% and 16.0% among current and former e-cigarette users respectively, 12.6% among ever users of heated tobacco products, and 27.0% and 14.2% among current and former waterpipe users respectively.
Table 1. Twelve-month prevalence of cannabis use for the total sample (weighted n = 9666) and stratified by sample characteristics.
| % [95% CI] | |
| Total | 4.6 [4.2; 5.1] |
|
Age in years 14–24 25–39 40–64 65+ |
11.4 [9.7; 13.3] 8.2 [7.1; 9.5] 3.1 [2.6; 3.6] 0.4 [0.2; 0.8] |
|
Sex Male Female |
6.4 [5.8; 7.2] 2.9 [2.4; 3.4] |
|
Educational attainment*1 Low Middle High |
3.9 [3.2; 4.8] 3.7 [3.1; 4.4] 6.0 [5.2; 7.0] |
|
Income*2 Low (< €1000) Middle (€1000–2333) High (> €2333) |
6.3 [5.3; 7.4] 4.3 [3.7; 4.8] 3.8 [3.1; 4.7] |
|
Migration background Yes (one or both parents born abroad) No |
6.6 [5.5; 7.9] 4.3 [3.8; 4.7] |
|
Region of residence*3 Rural (< 20 000 inhabitants) Urban (20 000–500 000 inhabitants) Metropolitan (> 500 000 inhabitants) |
3.3 [2.8; 3.9] 4.5 [3.9; 5.2] 8.2 [6.9; 9.7] |
|
Federal states cluster*4 Northwest Northeast Southwest Southeast |
5.1 [4.4; 5.9] 4.5 [3.4; 5.9] 3.9 [3.3; 4.5] 6.6 [4.9; 8.6] |
|
Use of tobacco Current Former Never |
10.2 [9.2; 11.3] 2.9 [2.1; 3.8] 1.1 [0.8; 1.4] |
|
Use of e-cigarettes Current Former Never |
13.3 [9.0; 18.6] 16.0 [14.0; 18.1] 2.7 [2.4; 3.1] |
|
Use of heated tobacco products Ever (current or former) Never |
12.6 [10.2; 15.3] 4.1 [3.7; 4.5] |
|
Use of waterpipes Current Former Never |
27.0 [21.6; 32.8] 14.2 [12.6; 15.9] 1.7 [1.4; 2.0] |
Percentages are presented within each stratum, e.g., 11.4% of 14- to 24-year-olds used cannabis in the past 12 months. 95% CI, 95% confidence interval
*1 Low, no qualification or junior high school equivalent; middle, secondary school equivalent (year 10); high, university entrance qualification or advanced technical college equivalent
*2 Details: https://osf.io/387fg
*3 Details: https://osf.io/zp7c6
*4 Northwest: Bremen, Hamburg, Lower Saxony, North Rhine–Westphalia, Schleswig–Holstein; northeast: Berlin, Brandenburg, Mecklenburg–Western Pomerania, Saxony–Anhalt; southwest: Baden–Württemberg, Bavaria, Hesse, Rhineland–Palatinate, Saarland; southeast: Saxony, Thuringia (a clustering similar to a previous study [36])
Table 2 shows the preferred route of administration in past-year users (unweighted n = 459). Smoking cannabis was reported by 92.4% [89.6; 94.6%], including 82.8% [79.0; 86.1%] who mostly smoke cannabis with tobacco and 9.6% [7.1; 12.7%] who mostly smoke cannabis without tobacco.
Table 2. Prevalence of preferred route of cannabis administration in past-year users (n = 459).
| % [95% CI] | |
| Smoking with tobacco, e.g., with joints or pipes | 82.8 [79.0; 86.1] |
| Smoking without tobacco, e.g., with joints or pipes | 9.6 [7.1; 12.7] |
| Inhaling without tobacco, e.g., with e-cigarettes or vaporizers | 1.7 [0.8; 3.4] |
| Consumption together with food | 2.0 [0.9; 3.7] |
| Consumption in a different form | 2.6 [1.4; 4.5] |
Percentages are presented within the total group of past-year users. 1.3% (n = 6) with missing data. 95% CI, 95% confidence interval
Due to the low rates for routes of administration other than smoking, we clustered and compared the rates of smoking cannabis with or without tobacco vs. other routes of administration by sample characteristics (Table 3). This clustering had not been prespecified in our original study protocol. We observed rates of smoking cannabis above the average (92.4%) among 14- to 24-year-olds (96.5%); among persons with migration background (97.6%); and among co-users, in particular among current users of waterpipes (97.1%).
Table 3. Prevalence of smoking cannabis with or without tobacco as the preferred route of cannabis administration in past-year users (n = 459) and stratified by sample characteristics.
| % [95% CI] | |
| Total | 92.4 [89.6; 94.6] |
|
Years of age 14–24 25–39 40–64 65+ |
96.5 [91.2; 99.0] 93.2 [88.5; 96.4] 91.6 [86.0; 95.4] 60.0 [32.3; 83.7] |
|
Sex Male Female |
93.9 [90.6; 96.4] 89.6 [83.8; 93.8] |
|
Educational attainment*1 Low Middle High |
90.2 [82.2; 95.4] 93.9 [89.0; 97.0] 92.1 [87.2; 95.5] |
|
Income*2 Low (< €1000) Middle (€1000–2333) High (> €2333) |
92.0 [86.7; 95.7] 93.5 [89.1; 96.5] 91.4 [83.8; 96.2] |
|
Migration background Yes (one or both parents born abroad) No |
97.6 [91.7; 99.7] 91.4 [88.0; 94.0] |
|
Region of residence*3 Rural (< 20 000 inhabitants) Urban (20 000–500 000 inhabitants) Metropolitan (> 500 000 inhabitants) |
93.4 [87.4; 97.1] 90.4 [85.6; 94.1] 94.6 [89.1; 97.8] |
|
Federal states cluster*4 Northwest Northeast Southwest Southeast |
94.8 [90.9; 97.4] 90.6 [80.7; 96.5] 90.3 [84.5; 94.5] 89.7 [72.6; 97.8] |
|
Use of tobacco Current Former Never |
95.6 [93.0; 97.5] 76.7 [61.4; 88.2] 82.4 [69.1; 91.6] |
|
Use of e-cigarettes Current Former Never |
91.7 [77.5; 89.2] 94.8 [90.3; 97.6] 90.8 [86.6; 94.1] |
|
Use of heated tobacco products Ever (current or former) Never |
95.1 [88.0; 98.7] 91.8 [88.5; 94.3] |
|
Use of waterpipes Current Former Never |
97.1 [89.9; 99.6] 93.7 [89.8; 96.4] 88.2 [81.9; 92.8] |
Percentages are presented within each stratum, e.g., 96.5% of 14- to 24-year-olds smoked cannabis with or without tobacco. 95% CI, 95% confidence interval
*1 Low, no qualification or junior high school equivalent; middle, secondary school equivalent (year 10); high, university entrance qualification or advanced technical college equivalent
*2 Details: https://osf.io/387fg
*3 Details: https://osf.io/zp7c6
*4 Northwest: Bremen, Hamburg, Lower Saxony, North Rhine–Westphalia, Schleswig–Holstein; northeast: Berlin, Brandenburg, Mecklenburg–Western Pomerania, Saxony–Anhalt; southwest: Baden–Württemberg, Bavaria, Hesse, Rhineland–Palatinate, Saarland; southeast: Saxony, Thuringia (a clustering similar to a previous study [36])
Discussion
Our national household survey showed that 4.6% of the population of Germany aged 14 or older had used cannabis in the past year, 2.2% in the past month. Past-year cannabis use was more common among co-users, particularly in current users of e-cigarettes and waterpipes. About nine out of ten respondents predominantly consumed cannabis by smoking, and mixing with tobacco was the most common form of consumption. Smoking cannabis versus other routes of administration was more common among 14- to 24-year-olds, persons with migration background, and co-users, particularly those who were current users of waterpipes.
In our sample of persons aged 14 years or more (including a large group of persons aged 65+ years) and using aggregated data over a period of approximately 1 year (April 2022 to February 2023), we estimated a past-year prevalence of cannabis use of 4.6%. Another general population survey, conducted in Germany from May to September 2021 and restricted to a sample aged 18–64 years, reported a past-year prevalence of 8.8%. Various survey methods were used (in writing, online, or by telephone) (4). Another recent study, conducted in Germany from April to June 2021 and based on telephone interviews, reported past-year rates of 7.6% in 12- to 17-year-olds and 25.0% in 18- to 25-year-olds (3). Our estimate of 11.4% in 14- to 24-year-olds was somewhat lower (but in between the two prevalences). These discrepancies in prevalence may be explained by differences between the studies in their periods of data collection, the age ranges of their respondents, and their survey methods. With regard to the survey methods, the methods used in our study could have led to slight underestimation of the actual prevalence, because some persons—particularly the young—may not feel comfortable reporting illegal behavior.
We observed higher rates of cannabis use in co-users, particularly in current users of e-cigarettes (13.3%) and waterpipes (27.0%). Previous international studies also showed that cannabis use is more common in smokers than in non-smokers (25). One mechanism that links the two products is that they are mostly consumed via the same route (26, 27). The co-use of cannabis and inhaled nicotine and tobacco products is of concern because of the increased risk of health problems. A longitudinal cohort study in young adults, for example, showed additive effects of cannabis use and tobacco smoking on lung function (28).
Smoking cannabis with tobacco was the predominant route of administration in our study; only 1.7% preferred to vape cannabis. In our previous study, 7.2% of current e-cigarette users reported that they had ever used e-cigarettes to vaporize cannabis (29). The Global Drugs Survey 2014 reported that 87.2% of cannabis users in Germany usually smoke cannabis with tobacco and 2.2% vape cannabis (23). Hence it seems that preferred routes of administration have not changed much in Germany in recent years. This is in contrast to the USA and Canada, where vaping cannabis is much more common and has increased recently in adolescents and young adults (16, 23, 30, 31). A possible reason for this difference is that the use of e-cigarettes is generally much lower in Germany (32) than in the USA (33) and Canada (34). Studies from the USA show that 62% of adolescent cannabis users (17) and 34% of adult cannabis consumers use multiple routes (19).
Our study has several limitations. We relied on self-reported data collected by face-to-face interviews. These data can be biased due to socially desirable response behavior, especially on the part of younger interviewees, as the use of cannabis is currently illegal in Germany. This bias may be higher in our study, in which face-to-face interviews were conducted, than in other studies featuring methods of data acquisition such as telephone interviews or online questionnaires, which create a more confidential environment. A recent study conducted in Sweden suggested that traditional approaches like ours may result in underestimating past-year cannabis use prevalence by 50% (35). Furthermore, 8% of the sample refused to answer our questions on cannabis. If use of cannabis was the reason for not responding, our prevalence figures are underestimated. We therefore conducted a post-hoc sensitivity analysis assuming that 50% of non-responders are past-year cannabis users. This doubled the estimated prevalence from 4.6% to 8.4% overall. It should be noted, however, that the assumed 50% usage rate among non-responders was arbitrary, as the real rate is unknown. Furthermore, underreporting of cannabis use can also result from respondents not telling the truth. Another limitation is that we only asked for the preferred route of administration. It is obvious that cannabis users may use various routes of administration, but with only one item we were not able to distinguish between different combinations of routes. We were also unable to separate medical from recreational use, which may also determine the preferred route of administration.
In conclusion, our study provides timely and relevant data on the baseline situation regarding the use of cannabis and co-use of inhaled nicotine and tobacco products prior to the forthcoming legalization of cannabis for recreational consumption in Germany. Further monitoring of the use of these products during the coming years will be of high importance in order to detect beneficial or adverse effects of the law changes. Any plans by the federal government to legalize recreational cannabis should be accompanied by preventive and harm-reduction efforts regarding the health risks of combined cannabis and tobacco, e-cigarette, and waterpipe use.
Acknowledgments
Funding
The DEBRA study was funded from 2016 to 2019 (waves 1–18) by the Ministry of Innovation, Science, and Research of the German federal state of North Rhine–Westphalia (MIWF) in the context of the “NRW Rückkehrprogramm” (the North Rhine–Westphalian postdoc return program). Since 2019 (wave 19 onwards), the study has been funded by the German Federal Ministry of Health.
Footnotes
Conflict of interest statement
JM has worked as consultant for and received honoraria from public health agencies; furthermore, he was involved in designing a study protocol for an experimental pilot study for licenced cannabis sales, funded by the federal state of Berlin (Germany).
EH is consultant to the EMCDDA and WHO, conducts cannabis-related research funded by the German Federal Ministry of Health, developed a cannabis treatment guideline funded by German scientific medical associations, and gives talks and training sessions on the therapeutic use of cannabis and treatment of cannabis use disorders in the public health system. She is president of the German Society for Addiction Research.
The remaining authors declare that no conflict of interest exists.
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