A systematic review of medical students’ and professionals


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Weisman and Rodríguez J Cannabis Res (2021) 3:47 https://doi.org/10.1186/s42238-021-00100-1

Journal of Cannabis Research

REVIEW

Open Access

A systematic review of medical students’ and professionals’ attitudes and knowledge regarding medical cannabis
Jared M. Weisman1,2*  and Marcus Rodríguez1,3 

Abstract 
Background:  Recently, the renewed global interest in cannabis’ therapeutic properties has resulted in shifting attitudes and legislative policies worldwide. The aim of this systematic review is to explore the existing literature on medical professionals’ and students’ attitudes and knowledge regarding medicinal cannabis (MC) to assess any relevant and significant trends.
Methods:  This systematic review was conducted in accordance with PRISMA guidelines. Using PubMed and Google Scholar, a literature search was performed to identify studies pertaining to healthcare professionals’ and medical students’ knowledge and attitudes regarding MC. There were no search limits on the year of publication; however, studies without primary data (e.g., abstracts, systematic reviews, meta-analyses) and non-English language papers were excluded. Studies were coded according to the following research questions: (1) Do respondents believe that cannabis should be legalized (for medicinal and/or recreational purposes)? (2) Are respondents confident in their level of knowledge regarding cannabis’ clinical applications? (3) Are respondents convinced of cannabis’ therapeutic potential? 4) What current gaps in knowledge exist, and how can the medical community become better informed about cannabis’ therapeutic uses? and (5) Are there significant differences between the knowledge and opinions of healthcare students versus healthcare professionals with respect to any of the aforementioned queries? Chi-square tests were used to assess differences between medical students and medical professionals, and Pearson’s bivariate correlations were used to analyze associations between survey responses and year of publication—as a proxy measurement to assess change over time.
Results:  Out of the 741 items retrieved, 40 studies published between 1971 and 2019 were included in the final analyses. In an evaluation of 21 qualified studies (8016 respondents), 49.9% of all respondents favored legalization (SD = 25.7, range: 16–97%). A correlational analysis between the percentage of survey respondents who support MC legalization and year of publication suggests that both medical students’ and professionals’ support for MC legalization has increased from 1991 to 2019 (r(19) = .44, p = .045). Moreover, medical professionals favor the legalization of MC at a significantly higher rate than students (52% vs. 42%, respectively; χ2 (1, N = 9019) = 50.72 p < .001). Also, respondents consistently report a strong desire for more education about MC and a substantial concern regarding MC’s potential to cause dependence and addiction. Pearson’s correlations between year of publication and survey responses for both of these queried variables suggest minimal changes within the last decade (2011–2019 for addiction and dependence, 2012-2019 for additional education; r(13) = − .10, p = .713 and r(12) = − .12, p = .678, respectively).
*Correspondence: [email protected] 2 MCR Labs, LLC, Framingham, MA, USA Full list of author information is available at the end of the article
© The Author(s) 2021. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://​creat​iveco​mmons.​org/​licen​ses/​by/4.​0/.

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Conclusion:  The finding that both medical students’ and professionals’ acceptance of MC has significantly increased in recent decades—in conjunction with their consistent, strong desire for more educational material—suggests that the medical community should prioritize the development of MC educational programs. MC is far more likely to succeed as a safe and viable therapy if the medical professionals who administer it are well-trained and confident regarding its clinical effects. Limitations include a lack of covariate-based analyses and the exclusion of studies published after the literature search was performed (June 2019). Future research should analyze studies published post-2019 to draw temporal comparisons and should investigate the effect of numerous covariates (e.g., gender, religiosity, prior cannabis use) as newer studies gather data on these factors [PROSPERO Registration: CRD42020204382].
Keywords:  Medical cannabis, Cannabis policy, International comparisons, Medical students, Medical professionals, Attitudes

Background Archaeological inquiry has revealed that cannabis use has been pervasive throughout human society for at least five millennia. In fact, it was widely used as a medical therapy in the USA in the 19th and early 20th centuries and was first incorporated into the United States Pharmacopoeia in 1850 (Bridgeman and Abazia 2017). The first federal restrictions on cannabis occurred in 1937 with the passage of the Marihuana Tax Act, which heavily regulated its usage and sale. Subsequently, cannabis was dropped from the United States Pharmacopoeia in 1942, and legal penalties for its possession increased in 1951 and 1956 with the enactment of the Boggs and Narcotic Control Acts, respectively. Finally, the Controlled Substances Act of 1970 relegated cannabis to Schedule I status at the federal level, imposing limitations on research by restricting the procurement of cannabis for research purposes (Bridgeman and Abazia 2017). Moreover, cannabis remains illegal under international law. From 1961 to 2020, The United Nations’ Single Convention on Narcotic Drugs (1961) placed cannabis and its derivative products in Class IV: the most restrictive category—analogous to the DEA’s Schedule I designation (United Nations 1964). However, in December 2020, the UN Commission on Narcotic Drugs reclassified cannabis and cannabis resin to recognize its medicinal value. Reclassification will rescind some longstanding procedural barriers to research and development of cannabisbased medicinal products; however, it will not affect its recreational use or promote legalization, and it will remain under strict international control. According to international law, cannabis will now be classified as having a similar degree of abuse and dependence potential as opiate-based drugs such as morphine and oxycodone (World Health Organization 2020).
Notwithstanding, as of May 2021, 36 US states, 4 US territories, the District of Columbia, and several dozen nations around the world have passed laws permitting the renewed medicinal usage of cannabis (Bifulco and Pisanti 2015; Hanson 2021). Fortunately, dozens of studies

assessing healthcare professionals’, medical students’, and patients’ knowledge and attitudes towards medicinal cannabis (MC) have been published in that time frame. Several such studies predate the first legislative bill legalizing MC in California (in 1996), and many studies were conducted between 1996 and 2019, when 32 other states and several countries—including Canada, Australia, and Ireland—legalized MC (Bridgeman and Abazia 2017; Crowley et al. 2017; Fischer et al. 2015; Hanson 2021; Thomsen 2016).
Notably, in 2019, Gardiner et al. published the first systematic review of health professionals’ beliefs, knowledge, and concerns surrounding MC (Gardiner et al. 2019). They found that healthcare providers generally supported MC use, despite a nearly unanimous lack of self-perceived knowledge regarding all of its clinical effects. Additionally, a preponderance of respondents voiced concerns about cannabis’ direct harm to patients and its indirect societal harms. While Gardiner et al.’s review provides a valuable compendium of data regarding health professionals’ general attitudes and knowledge of MC, this review broadens the scope of theirs by additionally assessing the responses of healthcare students. Furthermore, this review expands upon the following three questions investigated by Gardiner et al.: (1) How do health professionals feel about the use of MC in clinical practice? (2) How knowledgeable are health professionals regarding MC? and (3) What concerns exist for health professionals regarding the delivery of MC? With respect to question one, this review seeks to expand the scope of Gardiner et al.’s query by independently assessing respondents’ opinions regarding: medicinal versus recreational legalization; potential federal rescheduling; and clinical efficacy. With respect to question two, this review expands the scope of Gardiner et al.’s query by assessing both respondents’ self-reported knowledge regarding MC and assessing their desire for further education. Finally, with respect to question three, this review specifically assesses respondents’ concerns regarding MC’s potential to cause addiction and

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dependence—thereby expanding upon Gardiner et al.’s generalized query and seeking to inform future policy by addressing one of MC’s most pressing and pointed issues.
Additionally, in 2021, Zolotov et al. published a scoping review exploring the status of MC education among healthcare trainees (Zolotov et al. 2021). Their review of 23 studies across ten countries found that healthcare trainees lack sufficient knowledge about MC and do not feel prepared to counsel patients on the subject. They also found that deans and educational faculty agree on the need to educate students on MC, with an emphasis on a competencies-based curriculum. While Zolotov et al.’s review provides the most detailed investigation into MC education to date, this review expands upon their study by analyzing previously unaddressed temporal, geographic, and demographic factors. Moreover, this study provides a holistic review of MC literature, with education being one topic among several which are considered and analyzed.
Ultimately, the limited scope of Gardiner et al. and Zolotov et al.’s reviews—in addition to a preexisting wealth of published, peer-reviewed survey data addressing several other specific issues—led to the formation of the following seven guiding research questions which constituted the backbone of this novel systematic review.
1. Do you believe that physicians deserve the legal right to prescribe cannabis to patients? (i.e., Do you believe that cannabis should be legalized for therapeutic purposes?)
2. Do you believe that cannabis has any therapeutic utility?
3. Do you believe that cannabis should be legalized for recreational use?
4. [For US-based papers only] Do you believe that the USA should amend cannabis’ federal status as a Schedule 1 controlled substance (the most restrictive classification, asserting that the substance has no accepted medical use)?
5. Do you feel confident in your level of knowledge regarding the health effects of cannabis?
6. Do you desire additional education regarding MMJ and/or do believe that education on (medical) cannabis should be made readily available to medical professionals?
7. Are you concerned about cannabis’ dependence/ addiction potential?
In light of the legislative hurdles and cultural stigmatization surrounding cannabis, we hope this systematic review will provide an important framework for better understanding how the medical community can work to overcome sociocultural obstacles which currently

impede the acceptance of MC and other emergent, alternative therapies.
Methods Using both Google Scholar and PubMed, a literature search was performed between July 4th, 2019, and September 12th, 2019, to identify studies investigating healthcare students’ and professionals’ knowledge and attitudes regarding cannabis. Studies which solicited the opinions of physicians, nurses, physician’s assistants, pharmacists, and medical and pharmacy students were all deemed relevant. The searches utilized three main keyword categories: (1) keywords pertaining to various respondent types (e.g., “physician” or “health professional”); (2) keywords identifying specific types of response solicitation (e.g., “attitudes” or “opinions”); and (3) keywords corresponding to various substance-related topics (e.g., “cannabis” or “cannabinoids”). A comprehensive list of all the keywords utilized in the literature searches is provided in Appendix A. Moreover, the reference lists of selected papers were assessed to identify additional studies of relevance, and both databases provide investigators with extensive lists of related studies— helping to augment the simple keyword search protocol. The entire protocol was conducted in accordance with PRISMA guidelines and was registered and added to the University of York’s PROSPERO systematic review database, and given the ID number: CRD42020204382.
Studies met criteria for inclusion if they satisfied all of the following requirements: (1) they were complete, primary data studies rather than abstracts, meta-analyses, or systematic reviews; (2) they provided relevant data with respect to one or more of the aforementioned guiding research questions; (3) they were published in English; and (4) they contained medical professional or student respondents only; or, if a study included mixed groups with non-medical professionals or students, it segregated and sorted data based on one’s status as a medical professional or non-medical professional. Studies were excluded from further analyses if they failed to meet any one of these four specified requirements (see Fig. 1). There were no fixed search limits regarding year of publication. Overall, out of the 741 studies retrieved in the literature search, 40 studies were identified as meeting all the necessary inclusion criteria (see Table 1). The Cochrane Collaboration Risk of Bias Assessment Tool (version 2) was used to assess the risk of bias for each study (see Table 2) (Higgins et al. 2021). This tool investigates the following primary sources of bias: selection bias, performance bias, detection bias, attrition bias, and reporting bias. The Cochrane Risk of Bias Assessment Tool outlines the following criteria for assessing for risk of bias in studies: sequence generation (selection

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Fig. 1  Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram of included studies

bias), allocation concealment (selection bias), blinding of participants and personnel (performance bias), blinding of outcome assessment (detection bias), incomplete outcome data (attrition bias), selective outcome reporting (reporting bias) and other potential sources of bias. Each entry was coded as “high risk” and “low risk,” or “unclear” if there was insufficient information to determine potential bias. Several criteria—including allocation concealment, blinding of participants and personnel, and blinding of outcome assessment—unanimously received ratings of “unclear” due to the nature of the survey-based studies under review.
Data from studies which met all the inclusion criteria were subsequently logged and organized on a master

spreadsheet. While sorting through papers to extract data pertaining to the seven guiding research questions, it became apparent that while most papers addressed similar topics, they often phrased their questions in slightly different ways. For example, Chan et al. (2017) asked respondents to either agree or disagree with the following statement: “physicians should recommend marijuana as medical therapy,” whereas other researchers, such as Ananth et al. (2018), asked respondents to state whether or not they—as physicians—would be willing to prescribe marijuana to a patient (Ananth et al. 2018; Chan et al. 2017). Although these survey questions may not be exactly analogous, they both address the question of whether or not physicians

Table 1  Tabulated data from each of the studies included in the systematic review

Study

Country (state)

Total #

Participant Mean age

participants type

% male

Q1: Legal MC (% yes)

Ablin (2016) Israel

23

Rheumatolo- 45

78

N/A

gists

Ananth

USA

288

Pediatric

35

15

92

(2018)

oncologists

Balneaves Canada

182

NP’s

N/A

N/A

97

(2018)

Bega (2017) Multi-

56

Neurologists N/A

55

70

national

Berlekamp USA (OH) 319

Pharmacy N/A

N/A

N/A

(2019)

students

Braun (2018) USA

237

Oncologists N/A

66

N/A

Burke (1971) USA

1586

Med &

N/A

N/A

16

pharmacy

students

Caligiuri

USA (IA)

238

Pharmacy N/A

29

N/A

(2018)

students

Carlini (2015) USA (WA) 494

Mixed pro- N/A

31

72

fessionals

Chan (2017) USA (CO) 236

Medical

<30

52

74

students

Charuvastra USA

960

Mixed physi- N/A

N/A

36

(2005)

cians

Cogswell

USA (CA)

175

Medical

<30

23

N/A

(2015)

students &

social work-

ers

Crosby

USA (WA) 120

Healthcare <24

11

N/A

(2018)

students

Crowley

Ireland

565

GP’s

N/A

49

59

(2017)

Doblin

USA

978

Oncologists N/A

N/A

53

(1991)

Ebert (2015) Israel

72

Mixed physi- 51

65

83

cians

Fitzcharles Canada

128

Rheumatolo- 45

57

N/A

(2014)

gists

Hwang (2016)

USA (MN) 738

Pharmacists 49

N/A

N/A

Q2: Therapeutic Utility (% yes)

Q3: Recreational (%yes)

Q4: Amend Schedule I (% yes)

Q5: Knowledge (% yes)

Q6: Education (% yes)

74

N/A

N/A

26

N/A

92

N/A

N/A

N/A

N/A

72

N/A

N/A

N/A

76

N/A

50

52

N/A

93

N/A

44

N/A

N/A

N/A

67

N/A

N/A

29

N/A

N/A

41

57

66

N/A

N/A

N/A

74

N/A

86

64

N/A

N/A

24

N/A

N/A

16

77

72

N/A

96

72

N/A

91

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

69

N/A

63

N/A

79

23

N/A

N/A

43

N/A

N/A

63

N/A

N/A

N/A

N/A

54

70

N/A

N/A

80

89

N/A

26

N/A

N/A

10

N/A

Q7: Addiction (% yes)
N/A 37 N/A N/A N/A N/A N/A
N/A 62 88 N/A N/A
N/A N/A N/A N/A N/A 49

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Weisman and Rodríguez J Cannabis Res (2021) 3:47

Table 1  (continued)

Study

Country (state)

Total #

Participant Mean age

participants type

% male

Jacobs (2019)

Australia

86

Psychiatrists N/A

57

Karanges Australia

640

GP’s

N/A

33

(2018)

Kondrad

USA (CO) 520

Family physi- 50

56

(2013)

cians

Kusturica Serbia

316

Medical

N/A

32

(2019)

students

Lieff (1973) USA (MA) 35

Mixed physi- N/A

N/A

cians

Linn (1989) USA

303

Mixed physi- 48

87

cians

Luba (2018) USA

426

Mixed medi- 49

43

cal profes-

sionals

Martins

USA

137

Mixed medi- 39

44

(2017)

cal profes-

sionals

Mathern

Multi-

776

Mixed physi- N/A

N/A

(2015)

national

cians

Michalec

USA (DE)

87

(2015)

Mixed physi- >50

78

cians

Mitchell

Canada

769

Hospital

41

41

(2016)

pharmacists

Moeller

USA

311

Pharmacy N/A

39

(2015)

students

Norberg

Australia

664

GP’s (503) & 48

21

(2012)

Nurses (162)

Philpot

USA (MN) 62

Mixed physi- 46

57

(2019)

cians & PA’s

Ricco (2017) USA (MN) 60

Family Physi- N/A

N/A

cians

Schwartz USA

1122

Oncologists 47

N/A

(1997)

Sideris (2018) USA (NY) 164

Mixed physi- N/A

63

cians

Q1: Legal MC (% yes)
N/A

Q2: Therapeutic Utility (% yes)

Q3: Recreational (%yes)

Q4: Amend Schedule I (% yes)

Q5: Knowledge (% yes)

Q6: Education (% yes)

86

N/A

N/A

N/A

N/A

57

44

N/A

N/A

10

N/A

19

67

30

37

N/A

92

76

82

N/A

N/A

65

N/A

69

N/A

48

N/A

N/A

N/A

N/A

N/A

41

N/A

N/A

N/A

N/A

89

N/A

N/A

N/A

N/A

Q7: Addiction (% yes)
58 56 86 62 N/A N/A N/A

N/A

95

N/A

N/A

N/A

N/A

13

83

35

N/A

N/A

N/A

N/A

N/A

55

N/A

59

91

35

34

N/A

N/A

39

58

N/A

N/A

25

N/A

28

N/A

15

71

N/A

N/A

N/A

N/A

N/A

N/A

N/A

39

31

29

N/A

17

N/A

N/A

59

N/A

90

N/A

N/A

42

97

N/A

N/A

50

77

N/A

N/A

5

N/A

58

28

N/A

N/A

N/A

N/A

40

N/A

N/A

Page 6 of 20

Weisman and Rodríguez J Cannabis Res (2021) 3:47

Weisman and Rodríguez J Cannabis Res (2021) 3:47

Table 1  (continued)

Study

Country (state)

Total #

Participant Mean age

participants type

% male

Q1: Legal MC (% yes)

Q2: Therapeutic Utility (% yes)

Q3: Recreational (%yes)

Q4: Amend Schedule I (% yes)

Q5: Knowledge (% yes)

Q6: Education (% yes)

Q7: Addiction (% yes)

Stojanovic (2017)
Szyliowicz (2019)
Uritsky (2011)

Serbia USA (CA) USA

Ziemianski (2015)
Zylla (2018)
TOTAL

Canada
USA (MN) N/A

80

Pharmacy N/A

N/A

75

students

474

Pharmacists N/A

41

N/A

194
426
153 Total: 15,200 Mean: 380 SD: 345 Median: 263 IQR: 419 Range: 1563

Hospice medical professionals
Mixed physicians
Oncologists
N/A

47
N/A
N/A Mean: 43.81 SD: 4.812 Median: 47 IQR: 4 Range: 16

17
N/A
N/A Mean: 41.33 SD: 17.24 Median: 44 IQR: 26 Range: 76

91
85 N/A 49.9 (25.7)5

91 75 86
73 N/A 64.4 (18.7)5

N/A N/A 90
N/A N/A 36.5 (17.7)5

N/A

N/A

68

50

N/A

18

92

N/A

N/A

N/A

N/A

45

N/A

N/A

N/A 50.5 (15.4)5

63 41.0 (25.3)5

64
85 86.2 (13.8)5

N/A
N/A 57.8 (18.4)5

Note: GP general practitioner, PA physician’s assistants, NP’s nurse practitioners
*Fully-phrased questions: Q1 = Do you believe that physicians deserve the legal right to prescribe cannabis to patients? [i.e. Do you believe that cannabis should be legalized for therapeutic purposes?]; Q2 = Do you believe that cannabis has any therapeutic utility; Q3 = Do you believe that cannabis should be legalized for recreational use?; Q4 = [For US-based papers only] Do you believe that the USA should amend cannabis’ federal status as a schedule 1 controlled substance (the most restrictive classification, asserting that the substance has no accepted medical use)?; Q5 = Do you feel confident in your level of knowledge regarding the health effects of cannabis?; Q6 = Do you desire additional education regarding MMJ and/or do believe that education on (medical) cannabis should be made readily available to medical professionals?; Q7 = Are you concerned about cannabis’ dependence/addiction potential? 1 Weighted mean for all studies providing an exact integer value for mean age; 2 weighted SD 3 Pooled and weighted percent-male value; 4weighted SD in parentheses 5 Pooled and weighted percent-yes value; weighted SD in parentheses

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Table 2  Risk of bias assessment for all contributing studies

Study

Random sequence generation (selection bias)

Allocation concealment (selection bias)

Blinding of participants and personnel (performance bias)

Ablin, et al.

?

?

?

Ananth, et al.

?

?

?

Balneaves, et al. ?

?

?

Bega, et al.

?

?

?

Berlekamp, et al. ?

?

?

Braun, et al.



?

?

Burke & Marx

?

?

?

Caligiuri, et al.

?

?

?

Carlini, et al.

?

?

?

Chan, et al.

?

?

?

Charuvastra, et al. ?

?

?

Cogswell & Harris ?

?

?

Crosby

?

?

?

Crowley, et al.

?

?

?

Doblin & Kleiman ?

?

?

Ebert, et al.

?

?

?

Fitzcharles, et al. ?

?

?

Hwang, et al.

?

?

?

Jacobs, et al.

?

?

?

Karanges, et al.

?

?

?

Kondrad & Reid ?

?

?

Kusturica, et al.

?

?

?

Lieff, et al.



?

?

Linn, et al.

?

?

?

Luba, et al.

?

?

?

Martins , et al.

?

?

?

Mathern, et al.

?

?

?

Mitchell, et al.

?

?

?

Moeller & Woods ?

?

?

Norberg, et al.

?

?

?

Philpot, et al.

?

?

?

Rapp, et al.

?

?

?

Ricco, et al.

?

?

?

Schwartz, et al.

?

?

?

Sideris, et al.

?

?

?

Stojanovic, et al. ?

?

?

Szyliowicz, et al. ?

?

?

Uritsky, et al.

?

?

?

Ziemianski, et al. ?

?

?

Zylla, et al.

?

?

?

Key: ? = unclear risk X = high risk ✓ = low risk

Blinding of outcome assessment (detection bias)
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

Incomplete outcome data (attrition/ nonresponse bias)
? ? ? ? ? ✓ ✓ ? ? ? ? ✓ ? ? ? ? ? ? ? ? ? ✓ ? ? ? ? ? ? ✓ ? ? ? ? ? ? ✓ ? ? ? ?

Selective reporting (reporting bias)
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ? ✓ ✓ ✓ ✓ ✓ ✓ ? ✓ ✓ ✓ ? ✓ ✓ ✓

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should be allowed to authorize MC. Therefore, it was determined that both questions could be coded under the same category—in this instance, both were included in analyses related to research question 1: “Do healthcare professionals believe that cannabis should be legalized for medicinal purposes?” Similar judgment calls were made in numerous other instances when the phraseology of certain studies did not directly align with the phraseology used in the spreadsheet. A full layout of the phraseological sorting process—in accordance with the seven guiding research questions—is provided in Appendix B.
Statistical analyses Chi-square tests were used to assess the presence or absence of statistically significant differences between the two main survey cohorts: medical students and medical professionals. For these analyses, the total number of individual respondents from all the relevant studies who reported either “yes” or “no” to each research question were pooled into groups; then, a chi-square analysis determined if there were significant differences in the relative frequencies between each group. Additionally, Pearson’s r bivariate correlations were used to assess any relevant differences in entire studies’ responses to the research questions over time (i.e. by the year of the study’s publication). Furthermore, some temporal analyses (all using Pearson’s r bivariate correlations) assessed respondents’ opinions regarding MC with respect to the number of years preceding or following MC legalization in the state or country of the study’s publication. For these analyses, the year of MC legalization was identified for each state or country and labeled as “year 0”; then, the year of MC legalization was subtracted from the year of the study’s publication to yield the number of years distancing the study from the year of MC legalization. Finally, some temporal analyses featured a preponderance of studies conducted in a truncated time period— with only a few outlying studies published many years apart from the central cohort; in these instances, the outliers were excluded from analysis.
Results
Descriptive statistics In total, 40 studies provided data which were included in the final analyses; 26 studies were conducted exclusively in the USA, and the other 14 were conducted either multi-nationally or in countries other than the USA. The 40 studies produced a pool of exactly 15,200 respondents, yielding a mean of 380 respondents per study (SD = 345). For the studies which reported such statistics, there was an overall mean age of 43.8 years (SD = 4.81), with 41.3% of respondents being male (SD = 17.2). Overall, 8 studies

surveyed students only (20%), 31 surveyed medical professionals only (78%), and 1 surveyed both students and professionals (3%). Within the group of studies that only surveyed medical professional, 5 surveyed pediatric or adult oncologists (16%), 4 surveyed family physicians or general practitioners (13%), 3 surveyed pharmacists (10%), 2 surveyed rheumatologists (6%), 1 surveyed psychiatrists (3%), 1 surveyed exclusively nurse practitioners (3%), 1 surveyed hospice professionals (3%), 1 surveyed neurologists (3%), and 13 surveyed a mixed cohort of various medical professionals (42%). All studies included in the final analyses were evaluated for risk of bias according to the Cochrane Collaboration. While a preponderance of studies had an unclear risk of bias, none clearly expressed a high risk of bias which could threaten the review’s overall findings or conclusions (see Table 2, above).
Question 1: Do you believe that cannabis should be legalized for therapeutic purposes? An analysis of question 1 drew data from 21 studies (8016 respondents) published between 1991 and 2019. A Pearson’s bivariate correlation between a study’s year of publication and the percentage of respondents supporting MC legalization suggests that both medical students’ and professionals’ support for the legalization of MC increased over time (r(19) = .44, p = .045; Fig. 2). Out of the entire sample, 49.9% of all respondents favored legalization (SD = 25.7, range: 16–97%). The same correlational analysis amongst only medical professionals (following the removal of the 4 student-only studies) from studies published between 1991 and 2019 did not reach statistical significance (r(15) = .42, p = .093). Additionally, a correlational analysis between the number of years following or preceding MC legalization in the state or country of a study’s publication (within ±20 years) and the percentage of respondents supporting MC legalization did not meet statistical significance (r(7) = .53, p = .143).
A chi-square test comparing students’ (N = 1911, 5 studies) attitudes towards the legalization of MC against those of medical professionals (N = 7108, 18 studies) revealed a significant difference between the two cohorts, with medical professionals favoring legalization at a significantly higher rate than students (52% vs. 42%, respectively; χ2 (1, N = 9019) = 50.72, p < .001). Finally, a cross-national comparison of respondents’ attitudes regarding the legalization of MC reveals that levels of support markedly vary between countries; Canada demonstrated the greatest support for the legalization of MC (89%, N = 608, 2 studies), followed by Israel (83%, N = 71, 1 study), Serbia (76%, N = 396, 2 studies), Ireland (59%, N = 565, 1 study), and Australia (45%, N = 1304, 2 studies), while the USA

Weisman and Rodríguez J Cannabis Res (2021) 3:47

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Fig. 2  Medical students’ and professionals’ attitudes towards MC legalization, by year of study publication. Explanatory legend: Study question 1; 2 pre-1990 outliers removed; 21 studies total; r(19) = .44, p = .045

demonstrated the least support for the legalization of MC (42%, N = 5853, 13 studies).
Question 2: Do you believe that cannabis has any therapeutic utility? An analysis of research question 2 drew data from 26 studies (9,265 total respondents) and assessed respondents’ belief in cannabis’ medical utility. Out of the entire sample, 64.4% of all respondents espoused belief in cannabis’ therapeutic utility (SD = 18.7). A chisquare test comparing medical students’ (N = 1118, 5 studies) versus medical professionals’ (N = 7589, 21 studies) belief in cannabis’ medical utility yielded a significant difference, with students reporting greater confidence in cannabis’ medical utility than medical professionals (77% vs 65%, respectively; χ2 (1, N = 8707) = 62.72, p < .001). Additionally, a cross-national comparison of respondents’ belief in cannabis’ therapeutic utility revealed that levels of belief markedly vary between countries; Serbian respondents reported the highest rates of belief in cannabis’ medical utility (84%, N = 396, 2 studies), followed by Israel (82%, N = 95, 2 studies), the USA (70%, N = 5320, 16 studies), Ireland (68%, N = 565, 1 study), and Canada (63%, N = 1353, 3 studies), while Australian respondents reported the lowest rates of belief in cannabis’ medical utility (49%, N = 726; 2 studies).
Question 3: Should cannabis be legalized for recreational use? An analysis of research question 3 drew data from 11 studies (4754 total respondents) published between

1971 and 2019 and assessed whether medical students’ and professionals’ attitudes towards the legalization of recreational cannabis have changed over time. A Pearson’s correlation between year of publication and the proportion of respondents who support recreational legalization revealed no statistically-significant relationship (r(9) = .11, p = .746). Out of the entire sample, 36.5% of all respondents believed cannabis should be recreationally legalized (SD = 17.7). A chi-square test of medical students’ (N = 1834, 4 studies) versus medical professionals’ (N = 2302, 7 studies) support for recreational legalization yielded a statistically-significant difference, with students demonstrating greater support for recreational legalization than medical professionals (43% vs. 30%, respectively; χ2 (1, N = 4136) = 78.88, p < .001).
Question 4: Should the US federal government amend cannabis’ Schedule I status? An analysis of research question 4 drew data from 8 studies (5303 total respondents) and assessed US-based respondents’ opinions regarding the federal rescheduling of cannabis. Out of the entire sample, 50.5% of all respondents believed that the US federal government should amend cannabis’ Schedule I status (SD = 15.4). A chi-square test between medical students (N = 1204, 2 studies) and professionals (N = 3045, 5 studies) yielded a significant difference between each group’s level of support for the federal rescheduling of cannabis, with students supporting more lenient federal regulations at a higher rate than professionals (60% vs. 46%, respectively; χ2 (1, N = 4249) = 70.76, p < .001).

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A systematic review of medical students’ and professionals