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Medical cannabis use in Canadians with multiple sclerosis

  • Talia M Santarossa
    Affiliations
    EPICORE Centre, Department of Medicine, University of Alberta, 362 Heritage Medical Research Centre, University of Alberta, Edmonton, AB, Canada, T6G 2S2

    Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, 7-55 Medical Sciences Building, University of Alberta, Edmonton, AB, Canada, T6G 2H7
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  • Randy So
    Affiliations
    EPICORE Centre, Department of Medicine, University of Alberta, 362 Heritage Medical Research Centre, University of Alberta, Edmonton, AB, Canada, T6G 2S2

    Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, 7-55 Medical Sciences Building, University of Alberta, Edmonton, AB, Canada, T6G 2H7
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  • Dr Penelope Smyth
    Affiliations
    Division of Neurology, Department of Medicine, University of Alberta, 13-103 Clinical Sciences Building, University of Alberta, Edmonton, AB, Canada, T6G 2G3
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  • Dr Stefan Gustavsen
    Affiliations
    The Danish Multiple Sclerosis Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Valdemar Hansens Vej 2, 2600, Glostrup, Denmark
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  • Dr Ross T Tsuyuki
    Correspondence
    Corresponding author at: EPICORE Centre, Department of Medicine, University of Alberta, 362 Heritage Medical Research Centre, University of Alberta, Edmonton, AB, Canada T6G 2S2.
    Affiliations
    EPICORE Centre, Department of Medicine, University of Alberta, 362 Heritage Medical Research Centre, University of Alberta, Edmonton, AB, Canada, T6G 2S2

    Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, 7-55 Medical Sciences Building, University of Alberta, Edmonton, AB, Canada, T6G 2H7
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Published:January 27, 2022DOI:https://doi.org/10.1016/j.msard.2022.103638

      Highlights

      • Many people with multiple sclerosis seek alternative therapies such as cannabis.
      • Recreational cannabis use has been legal in Canada since 2018, which might affect access – for this reason, we surveyed Canadians on cannabis use.
      • We found that about two thirds of respondents used cannabis at least once, with 52% still currently using it.
      • Cannabis was used primarily for sleep disorders, pain and spasticity, with moderate to high effectiveness reported.

      Abstract

      Background

      : The extent of medical cannabis use by people with multiple sclerosis (MS) in Canada has not been evaluated for more than a decade since recreational cannabis was legalized. Legalization provided an avenue for those to whom legal cannabis was previously inaccessible to access it as an alternative therapy. Our objective was to evaluate the prevalence of medical cannabis use by Canadians with MS, the reasons it is used, adverse effects, as well as the context surrounding how it is obtained and where users learned about it.

      Methods

      : An anonymous questionnaire was distributed to prospective participants through various channels. The questionnaire included questions about participant characteristics and quality of life, their MS, and their medical cannabis use. It also employed two validated patient-reported outcome measures, the PDDS and the MSQOL-54.

      Results

      : Completed questionnaires were submitted by 344 individuals. Among respondents, 215/344 (64.5%) reported having used medical cannabis at least once, and 180 (52.3%) reported still currently using it. Based on disease and quality of life data, we found that respondents with more severe or progressive forms of MS were more likely to have tried medical cannabis. Medical cannabis was used most by current and former users to treat sleep problems (84.2%), pain (80.0%), and spasticity (68.4%), while the most reported adverse effects were drowsiness (57.2%), feeling quiet/subdued (48.8%), and difficulty concentrating (28.4%). Most current and former users obtained their cannabis from a legal, reliable source (76.1%) and many (74%) learned about medical cannabis from someone other than a healthcare provider.

      Conclusions

      : This study showed that nearly two-thirds of survey respondents, comprised of Canadians living with MS, have tried medical cannabis at least once and that those with a greater disease burden were more likely to have tried it. Users reported that cannabis is moderately to highly effective in treating several symptoms and that adverse effects are not generally severe, nor are they the main factor driving medical cannabis cessation. Our results support the need for more research examining medical cannabis use in MS and for evidence-based resources to be publicly available for those exploring it as a potential therapy.

      Keywords

      1. Introduction

      Canada legalized recreational cannabis in October of 2018. However, it has been legal for medical purposes since 2001, with over 230,000 individuals having acquired medical client registrations by early 20181. This legislation opened the door for those who may have previously been unable to obtain legal medical cannabis or who may have avoided it due to social stigma or a lack of access to reputable, regulated vendors. Owing to its purported benefits, including relief of spasticity, chronic pain, fatigue, anxiety, and depression (
      • Page S.A.
      • Verhoef M.J.
      • Stebbins R.A.
      • Metz L.M.
      • Levy J.C.
      Cannabis use as described by people with multiple sclerosis.
      ;
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ), cannabis is a popular alternative or complementary therapy among people with multiple sclerosis (MS), whose use of cannabis has been estimated as high as four times that of the general population (
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ). Despite its growing use in MS, evidence for the efficacy of cannabis-based medicines is rather weak (
      • Nielsen S.
      • Germanos R.
      • Weier M.
      • Pollard J.
      • Degenhardt L.
      • Hall W.
      • Buckley N.
      • Farrell M.
      The use of cannabis and cannabinoids in treating symptoms of multiple sclerosis: a systematic review of reviews.
      ).
      Most current clinical data concerning cannabinoid treatment of MS symptoms focuses on prescription preparations and not on whole-plant cannabis or other preparations associated with recreational use, such as ingestibles and concentrated products like resins. This excludes potential effects arising from terpenoids and other phytocannabinoids present in whole-plant cannabis as well as possible synergistic or entourage effects of these compounds (
      • Russo E.B.
      Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects.
      ). Evidence for the efficacy of cannabis-derived products in treating MS symptoms, including chronic pain, spasticity, tremor, and urinary incontinence, is inconclusive. This degree of variability is also seen in the treatments ested, sample sizes, and study designs. Insufficient data suggests that they are detrimental in this regard, although the degree of efficacy may not be large (
      • Nielsen S.
      • Germanos R.
      • Weier M.
      • Pollard J.
      • Degenhardt L.
      • Hall W.
      • Buckley N.
      • Farrell M.
      The use of cannabis and cannabinoids in treating symptoms of multiple sclerosis: a systematic review of reviews.
      ;
      • Koppel B.S.
      • Brust J.C.M.
      • Fife T.
      • Bronstein J.
      • Youssof S.
      • Gronseth G.
      • Gloss D.
      Systematic review: efficacy and safety of medical marijuana in selected neurologic disorders.
      ;
      • Yadav V.
      • Bever C.
      • Bowen J.
      • Bowling A.
      • Weinstock-Guttman B.
      • Cameron M.
      • Bourdette D.
      • Gronseth G.S.
      • Narayanaswami P.
      Summary of evidence-based guideline: complementary and alternative medicine in multiple sclerosis.
      ). Less conclusive evidence exists regarding the effects of cannabinoids in treating tremor, ataxia, and bladder function, where it currently appears that they are ineffective or only minimally effective (
      • Nielsen S.
      • Germanos R.
      • Weier M.
      • Pollard J.
      • Degenhardt L.
      • Hall W.
      • Buckley N.
      • Farrell M.
      The use of cannabis and cannabinoids in treating symptoms of multiple sclerosis: a systematic review of reviews.
      ).
      While there may be studies indicating that cannabinoids can be useful in treating certain MS symptoms, there is also evidence of adverse effects of cannabinoids in these individuals. Medical cannabis may negatively impact posture, balance (
      • Suryadevara U.
      • Bruijnzeel D.M.
      • Nuthi M.
      • Jagnarine DA
      • Tandon R.
      • Bruijnzeel A.W.
      Pros and cons of medical cannabis use by people with chronic brain disorders.
      ), and worsen cognitive impairment (
      • Suryadevara U.
      • Bruijnzeel D.M.
      • Nuthi M.
      • Jagnarine DA
      • Tandon R.
      • Bruijnzeel A.W.
      Pros and cons of medical cannabis use by people with chronic brain disorders.
      ;
      • Honarmand K.
      • Tierney M.C.
      • O’Connor P.
      • Feinstein A.
      Effects of cannabis on cognitive function in patients with multiple sclerosis.
      ). It has also been shown that people with MS who use cannabis are twice as likely as nonusers to be considered cognitively impaired (
      • Honarmand K.
      • Tierney M.C.
      • O’Connor P.
      • Feinstein A.
      Effects of cannabis on cognitive function in patients with multiple sclerosis.
      ). Furthermore, it has been suggested that smoked forms of cannabis have increased unfavorable effects upon processing speed and memory as compared to other forms of cannabis (
      • Feinstein A.
      • Banwell E.
      • Pavisian B.
      What to make of cannabis and cognition in MS: in search of clarity amidst the haze.
      ), while males with MS were shown to possibly experience more cognitive effects of cannabis as compared to females (
      • Patel V.P.
      • Feinstein A.
      Cannabis and cognitive functioning in multiple sclerosis: the role of gender.
      ). Reports of adverse effects from cannabis may include mild to moderate dizziness, dry mouth, diarrhea, and euphoria in people with MS (
      • Nielsen S.
      • Germanos R.
      • Weier M.
      • Pollard J.
      • Degenhardt L.
      • Hall W.
      • Buckley N.
      • Farrell M.
      The use of cannabis and cannabinoids in treating symptoms of multiple sclerosis: a systematic review of reviews.
      ). None of these adverse effects are severe enough to issue a blanket recommendation against cannabinoid therapy in people with MS. However, concerns have been raised regarding specific patient populations, for example, those who are cognitively impaired, the elderly, or those with psychosis (
      • Nielsen S.
      • Germanos R.
      • Weier M.
      • Pollard J.
      • Degenhardt L.
      • Hall W.
      • Buckley N.
      • Farrell M.
      The use of cannabis and cannabinoids in treating symptoms of multiple sclerosis: a systematic review of reviews.
      ).
      This cross-sectional study aimed to evaluate the prevalence of cannabis use in people with MS in Canada, its perceived efficacy in treating a variety of symptoms, and the frequency and severity of adverse effects. Importantly, this has not been evaluated in Canada since recreational cannabis was legalized in 2018, although somewhat comparable studies were published in 2003 and 2004 (
      • Clark A.J.
      • Ware M.A.
      • Yazer E.
      • Murray T.J.
      Lynch ME. Patterns of cannabis use among patients with multiple sclerosis.
      ,
      • Page S.A.
      • Verhoef M.J.
      • Stebbins R.A.
      • Metz L.M.
      • Levy J.C.
      Cannabis use as described by people with multiple sclerosis.
      ). Given that cannabis has therapeutic promise in managing MS symptoms, it is essential to learn about current patient experiences to inform future research endeavors to develop effective alternative therapeutic regimens of symptom management aiming to improve quality of life.
      The primary objective was to determine the prevalence of medical cannabis use among people with MS in Canada. Secondary objectives include determination of the symptoms it is most used to treat, the frequency and severity of adverse effects, and a comparison of the prevalence of medical cannabis use by people with MS between Canada and Denmark, where recreational cannabis is still illegal (
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ).

      2. Methods

      2.1 Ethics statement

      This study was approved by the University of Alberta Research Ethics Office (Study ID: MS2_Pro00101321).

      2.2 Questionnaire design

      The questionnaire used in this study was adapted from that employed by Gustavsen et al. to examine cannabis use by people with MS in Denmark (
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ). It was divided into three sections: participant characteristics and quality of life, information about participants’ MS, and cannabis use. Participant characteristics that were collected included age and sex. The quality of life sections employed a validated instrument for evaluating health-related quality of life, the Multiple Sclerosis Quality of Life-54 (MSQOL-54) (
      • Vickrey B.G.
      • Hays R.D.
      • Harooni R.
      • Myers L.W.
      • Ellison G.W.
      A health-related quality of life measure for multiple sclerosis.
      ). Under participants’ MS, we collected information related to clinical diagnosis, time since symptom onset and diagnosis, current medications, and degree of disability. The latter was assessed using the Patient Determined Disease Steps (PDDS) scale, a validated and non-copyrighted patient-reported outcome (
      • Learmonth Y.C.
      • Motl R.W.
      • Sandroff B.M.
      • Pula J.H.
      Cadavid D. Validation of patient determined disease steps (PDDS) scale scores in persons with multiple sclerosis.
      ). Finally, we collected information regarding participants’ use of cannabis to manage their MS symptoms. We defined medical cannabis as that used to manage MS symptoms, regardless of whether this was prescribed by a healthcare provider or self-selected. This included whether they have ever tried cannabis for their MS, how they learned about it, how they obtain it and in what form, how often they use it and for which symptoms, how effective it has been, and if they have experienced any adverse effects. If participants had never used cannabis to manage their MS symptoms or have stopped, they were asked why.

      2.3 Participant recruitment

      Using recent data that estimates that around 97,300 people in Canada are living with MS (
      • Gilmour H.
      • Ramage-Morin P.L.
      • Wong S.L.
      Multiple sclerosis: prevalence and impact.
      ), and assumptions of a 95% confidence level, a 10% margin of error, and a predicted 50% sample proportion having used medical cannabis based on previous data (
      • Koppel B.S.
      • Brust J.C.M.
      • Fife T.
      • Bronstein J.
      • Youssof S.
      • Gronseth G.
      • Gloss D.
      Systematic review: efficacy and safety of medical marijuana in selected neurologic disorders.
      ), a minimum sample size of 96 participants for this survey was calculated using a modified Cochran Formula. First, a group of 114 previous participants from an earlier study conducted by our research group (
      • Smyth P.
      • Watson K.E.
      • Tsuyuki R.T.
      Measuring the Effects of Nurse-Practitioner (NP) - Led Care on Depression and Anxiety Levels in People with Multiple Sclerosis : a Study Protocol for a Randomized Controlled Trial Trial Registration.
      ) who have agreed to be contacted regarding future studies were sent an invitation email containing the study information with a personalized link to the survey. Participants were also recruited from selected clinics in Alberta. Finally, the study was listed on the MS Society of Canada's research portal for MS Society members to access and posted across their social media accounts. To obtain the broadest cross-section of the population of people with MS and maximize the generalizability of the results, the only inclusion criteria were that participants live in Canada and have MS. There are no defined exclusion criteria.

      2.4 Statistical analysis

      Data analysis consisted of descriptive statistics. The sample population was characterized, and tests of homogeneity were performed to compare participant and disease characteristics between the groups of participants who have not, used to, and currently use medical cannabis to manage MS symptoms. The remaining data were analyzed in the same manner to determine the proportion of participants who have used medical cannabis, the perceived efficacy of cannabis in treating various symptoms, frequency and severity of adverse effects, what forms of cannabis are most used, and whether there were any significant differences between the responses of current and former users.
      Analysis was performed using R 3.4.0 (Vienna, Austria; https://www.R-project.org/) and SAS 9.4 software (SAS Institute Inc. Cary, NC, USA). Prior to analysis, data underwent preliminary screening in SAS to ensure that all surveys to be included in the analysis contained affirmative consent and that participants submitted the survey as complete. The process of screening the surveys for consent and completion is outlined in Fig. 1.
      Univariable analysis was used to test differences between participant groups using statistical hypothesis testing. For continuous variables, the independent T-test or Wilcoxon rank sum test were used (when data were heavily skewed; the assumptions of each test were verified ahead of time). For categorical variables, either the Pearson Chi-square or Fisher exact tests (when small frequencies present) were used. Data are reported as mean (standard deviation), median (interquartile range), and range for continuous variables and frequency (percentage) for categorical variables. P-values less than 0.05 were considered statistically significant.

      3. Results

      3.1 Participant characteristics

      In total, 344 respondents completed the questionnaire. Of those, 79.9% were female and the overall mean age was 44.9 years (± 11.3) (Table 1). More than three quarters (79.3%) of the participants were diagnosed with relapsing-remitting MS (RRMS), while 10.5% had secondary progressive MS (SPMS), and the remaining 10.2% either had primary progressive MS (PPMS) or did not know their diagnosis (Table 1). More than half of the participants (52.3%) were current users of medical cannabis at the time of questionnaire completion, while 10.2% were former users and 37.5% had never used it before. There were no significant differences in the sex, age, and length of time that respondents have been living with MS, with or without a diagnosis, between any of the groups of respondents (current users, former users, nonusers) (Table 1). There were, however, significant differences in the types of MS, whether respondents were prescribed disease-modifying treatments (DMTs), how inhibited they felt by their MS, and the PDDS and MSQOL-54 scores between nonusers and current users, and nonusers and former users (Table 1). No significant differences were detected between current and former users. Compared to nonusers, current and former users were more likely to have progressive forms of MS, were less likely to be using DMTs, felt more inhibited by MS in their daily lives, and were more disabled with lower quality of life, as measured by PDDS and MSQOL-54 scores (Table 1). Stated otherwise, those who have tried medical cannabis had a greater disease burden than those who have not.
      Table 1Participant Characteristics. Comparisons made between groups of participants were made using Chi-square and Fisher exact tests (*) for categorical variables and independent T-tests for continuous variables.
      VariableNonuser (n = 129)@N (%)Current User (n = 180)@N (%)Former User (n = 35)@N (%)P[email protected](Nonuser vs. Current User)P[email protected](Nonuser vs. Former User)P[email protected](Current User vs. Former User)Total (n = 344)@N (%)
      SexMale31 (24.03)32 (17.78)6 (17.65) (n = 34)0.17850. 42920.985469 (20.12) (n = 343)
      Female98 (75.97)148 (82.22)28 (82.35)274 (79.88)
      AgeMean (SD)@Median (IQR)@Range45.43 (10.56) (n = 127)@46.0 (36.0 – 53.0)@21.0 – 73.044.22 (11.69) (n = 172)@43.50 (34.50 – 53.0)@24.0 – 79.046.55 (11.51) (n = 33)@44.0 (3730 – 54.0)@290 – 68.00.34720.61740.293644.91 (11.25) (n = 332)@44.0 (36.0 – 53.0)@21.0 – 79.0
      Years since [email protected](as of end of 2020)Mean (SD)@Median (IQR)@Range10.88 (8.16) (n = 128)@9.0 (4.0 – 18.0)@0.0 – 36.010.29 (8.97) (n = 180)@8.0 (3.0 – 16.0)@0.0 – 50.010.94 (9.08) (n = 34)@9.0 (3.0 – 19.0)@0.0 – 30.00.55000.97300.704510.58 (8.66) (n = 342)@8.0 (3.0 – 17.0)@0.0 – 50.0
      Years since symptoms [email protected](as of end of 2020)Mean (SD)@Median (IQR)@Range14.22 (9.23) (n = 125)@13.0 (6.0 – 22.0)@0.0 (37.0)15.49 (10.15) (n = 178)@14.0 (8.0 – 22.0)@0.0 – 50.014.09 (9.97) (n = 34)@12.50 (7.0 – 20.0)@0.0 – 43.00.26080.94330.458114.88 (9.79) (n = 337)@14.0 (8.0 – 22.0)@0.0 – 50.0
      Type of multiple sclerosisRelapsing114 (88.37)134 (74.44)24 (70.59) (n = 34)0.00300.0332*0.2977*272 (79.30) (n = 343)
      Secondary Progressive4 (3.10)28 (15.56)4 (11.76)36 (10.50)
      Primary Progressive6 (4.65)7 (3.89)4 (11.76)17 (4.96)
      Do not know5 (3.88)11 (6.11)2 (5.88)18 (5.25)
      Disease-modifying medicalYes106 (82.17)118 (65.92) (n = 179)19 (55.88) (n = 34)0.0052*0.0049*0.4267243 (71.05) (n = 342)
      treatmentNo21 (16.28)56 (31.28)13 (38.24)90 (26.32)
      Not known2 (1.55)5 (2.79)2 (5.88)9 (2.63)
      Disease-modifying treatmentsInterferon-beta9 (8.33) (n = 108)6 (4.96) (n = 121)3 (15.79) (n = 19)0.0009
      Fisher exact test infeasible, Chi-square approximation may be incorrect.
      0.1929*0.6227*18 (7.26) (n = 248)
      Peginterferon0 (0.0)1 (0.83)0 (0.0)1 (0.40)
      Teriflunomide6 (5.56)15 (12.40)3 (15.79)24 (9.68)
      Dimethyl fumarate24 (22.22)12 (9.92)1 (5.26)37 (14.92)
      Natalizumab3 (2.78)5 (4.13)2 (10.53)10 (4.03)
      Rituximab0 (0.0)2 (1.65)0 (0.0)2 (0.81)
      Ocrelizumab24 (22.22)39 (32.23)5 (26.32)68 (27.42)
      Alemtuzumab2 (1.85)13 (10.74)0 (0.0)15 (6.05)
      Fingolimod5 (4.63)4 (3.31)1 (5.26)10 (4.03)
      Siponimod1 (0.93)2 (1.65)0 (0.0)3 (1.21)
      Cladribine1 (0.93)6 (4.96)1 (5.26)8 (3.23)
      Mitoxantrone0 (0.0)0 (0.0)0 (0.0)0 (0.0)
      Glatiramer acetate30 (27.78)13 (10.74)3 (15.79)46 (18.55)
      Do not know1 (0.93)0 (0.0)0 (0.0)1 (0.40)
      Other2 (1.85)3 (2.48)0 (0.0)5 (2.02)
      Feelings of Inhibition by MSNot at all24 (18.60)15 (8.33)1 (2.94) (n = 34)<0.00010.05190.326540 (11.66) (n = 343)
      A little63 (48.84)53 (29.44)15 (44.12)131 (38.19)
      Moderately23 (17.83)68 (37.78)11 (32.35)102 (29.74)
      Very Much19 (14.73)44 (24.44)7 (20.59)70 (20.41)
      PDDS Scores0. Normal52 (40.63) (n = 128)26 (14.44)4 (11.76) (n = 34)<0.0001
      Fisher exact test infeasible, Chi-square approximation may be incorrect.
      0.0106
      Fisher exact test infeasible, Chi-square approximation may be incorrect.
      0.9902*82 (23.98) (n = 342)
      1. Mild Disability33 (25.78)29 (16.11)7 (20.59)69 (20.18)
      2. Moderate Disability12 (9.38)36 (20.0)6 (17.65)54 (15.79)
      3. Gait Disability13 (10.16)27 (15.0)6 (17.65)46 (13.45)
      4. Early Cane6 (4.69)27 (15.0)6 (17.65)39 (11.40)
      5. Late Cane6 (4.69)12 (6.67)1 (2.94)19 (5.56)
      6. Bilateral Support5 (3.91)16 (8.89)3 (8.82)24 (7.02)
      7. Wheelchair/Scooter1 (0.78)7 (3.89)1 (2.94)9 (2.63)
      8. Bedridden0 (0.0)0 (0.0)0 (0.0)0 (0.0)
      MSQOL-54 Scores
      Overall Quality of LifeMean (SD)@Median (IQR)@Range67.36 (17.17)@68.35 (55.0 – 81.65)@28.65 – 100.058.38 (19.52)@60.0 (45.83 – 73.35)@8.35 – 100.053.88 (19.49) (n = 34)@55.0 (41.65 – 68.35)@8.35 – 86.65<0.00010.00060.222861.32 (19.24) (n = 343)@63.35 (50.0 – 76.65)@8.35 – 100.0
      Physical Health CompositeMean (SD)@Median (IQR)@Range62.16 (20.14) (n = 112)@64.09 (45.28 – 79.33)@14.02 – 95.9745.47 (18.85) (n = 157)@42.81 (31.60 – 36.35)@6.21 – 94.9245.61 (18.88) (n = 27)@46.49 (32.78 – 59.74)@10.20 – 78.99<0.00010.00020.971351.80 (20.92) (n = 296)@48.59 (35.34 – 67.54)@6.21 – 95.97
      Mental Health CompositeMean (SD)@Median (IQR)@Range63.34 (19.64) (n = 124)@66.59 (47.20 – 78.65)@18.28 – 97.9450.30 (21.70) (n = 177)@46.49 (33.49 – 65.59)@4.87 – 97.6048.03 (20.26) (n = 33)@47.92 (33.11 – 61.93)@11.19 – 87.92<0.00010.00030.562254.92 (21.76) (n = 334)@53.50 (37.90 – 72.04)@4.87 – 97.94
      # Fisher exact test infeasible, Chi-square approximation may be incorrect.

      3.2 Reasons for not using medical cannabis

      Among nonusers, the most common reasons for not trying medical cannabis were that they were unaware of the potential benefits (34.4%), they did not feel that they needed it or were uninterested in it (15%), and because of social stigma (14.4%) (Fig. 2A). A smaller number of individuals reported not having tried medical cannabis because of personal beliefs (11.9%), the cost or lack of accessibility (10%), concerns about potential complications or drug interactions (4.4%), or that they were either not allowed to or were advised against using medical cannabis (3.1%) (Fig. 2A). Conversely, among former users, the most common reasons for ceasing to use medical cannabis were cost and poor accessibility (34.4%), that they found medical cannabis ineffective for their purposes (28.6%), and that they experienced undesirable adverse effects (17.1%) (Fig. 2B). Fewer individuals cited other specific reasons for stopping medical cannabis use (14.3%) (Fig. 2B).
      Fig. 2:
      Fig. 2Reasons for not Using Medical Cannabis. Note the different y-axis scales in each panel. (A) Reasons cited by nonusers for not trying medical cannabis. Respondents could select multiple options (n = 158). (B) Reasons cited by former users for ceasing to use medical cannabis. Respondents could select multiple options (n = 35).

      3.3 Characteristics of medical cannabis use in people with MS

      Cannabis was most frequently obtained from licensed medicinal producers (31.3%) and recreational retail stores (29.4%) (Fig. 3A). Fewer people obtained it from recreational online stores (13.8%), unlicensed vendors (12%), or grew their own (8.9%). More than two-thirds (40.7%) of all responses to the question asking where participants learned about medical cannabis were attributed to personal research/self-medication or to social media, family, or friends (30.1%) (Fig. 3B). Most of the remaining answers indicated that they learned about medical cannabis through a healthcare provider, such as their neurologist, family physician, nurse practitioner, pharmacist, or another, while a small number learned about it through MS clinics, groups, or events (Fig. 3B). Similar numbers of participants reported using smoked or vaporized dried flower products (26.9%), concentrates (sublingual oil droppers or sprays, capsules) (30.7%), and ingestibles (tea, baked goods, beverages, candy/mints/chocolate) (36%), while far fewer report using extracts (hash, distillate, isolate, shatter/budder/diamonds/badder/hydrocarbon extracts) or prescription drug formulations (Fig. 3C). Finally, among current users, the vast majority (73.8%) report using medical cannabis products daily (Fig. 3D).
      Fig. 3:
      Fig. 3Medical Cannabis Use. Note the different y-axis scales in each panel. (A-C) Responses from both current and former users are combined. Multiple responses could be selected for each question. (A) Where participants reported obtaining their medical cannabis products(n = 326). (B) Where participants reported having learned about medical cannabis (n = 339). (C) Forms of cannabis used by participants for medical purposes (n = 505). (D) Only current users were queried about the frequency of their medical cannabis use and only one response could be selected (n = 164).

      3.4 Effectiveness of medical cannabis in treating selected symptoms

      Sleep problems were the most reported symptom that participants used medical cannabis for (84.1%), followed by pain (80%), spasticity (68.4%), stress (66.5%), and fatigue (59%) (Table 2). Over 80% of current users reported cannabis as being effective or highly effective in treating spasticity, pain, sleep problems, bad mood, and stress and 50–80% reported it as effective in treating anxiety, headache, and fatigue (Table 2). In all these cases, current users reported medical cannabis as being more effective than did former users (P<0.05, Table 2). Results were highly mixed regarding the treatment of sexual problems, but both over 90% of current and former users agreed that cannabis was effective or very effective in increasing appetite, while over 40% of current users and 100% of former users agreed that cannabis was either ineffective or only slightly effective in treating urination problems/difficulties (Table 2).
      Table 2Effectiveness of Medical Cannabis in Treating Selected MS Symptoms. Comparisons made between current and former users were made using Chi-square and Fisher exact tests (*).
      SymptomCurrent User (n = 180)Former User (n = 35)P-valueTotal (n = 215)
      N (%)N (%)N (%)
      Sleep problemsNot effective2 (1.29) (n = 155)6 (23.08) (n = 26)<0.0001*8 (4.42) (n = 181)
      Slightly effective14 (9.03)6 (23.08)20 (11.05)
      Effective52 (33.55)10 (38.46)62 (34.25)
      Very effective84 (54.19)4 (15.38)88 (48.62)
      Unsure3 (1.94)0 (0.0)3 (1.66)
      PainNot effective1 (0.70) (n = 143)7 (24.14) (n = 29)<0.0001*8 (4.65) (n = 172)
      Slightly effective22 (15.38)9 (31.03)31 (18.02)
      Effective64 (44.76)5 (17.24)69 (40.12)
      Very effective53 (37.06)7 (24.14)60 (34.88)
      Unsure3 (2.10)1 (3.45)4 (2.33)
      SpasticityNot effective3 (2.36) (n = 127)6 (30.0) (n = 20)<0.0001*9 (6.12) (n = 147)
      Slightly effective19 (14.96)6 (30.0)25 (17.01)
      Effective59 (46.46)4 (20.0)63 (42.86)
      Very effective43 (33.86)2 (10.0)45 (30.61)
      Unsure3 (2.36)2 (10.0)5 (3.40)
      StressNot effective2 (1.65) (n = 121)3 (13.64) (n = 22)0.0003*5 (3.50) (n = 143)
      Slightly effective15 (12.40)7 (31.82)22 (15.38)
      Effective52 (42.98)8 (36.36)60 (41.96)
      Very effective50 (41.32)2 (9.09)52 (36.36)
      Unsure2 91.65)2 (9.09)4 (2.80)
      FatigueNot effective10 (9.09) (n = 110)9 (52.94) (n = 17)0.000319 (14.96) (n = 127)
      Slightly effective36 (32.73)2 (11.76)38 (29.92)
      Effective39 (35.45)2 (11.76)41 (32.28)
      Very effective16 (14.55)2 (11.76)18 (14.17)
      Unsure9 (8.18)2 (11.76)11 (8.66)
      AnxietyNot effective2 (1.89) (n = 106)4 (40.0) (n = 10)0.00036 (5.17) (n = 116)
      Slightly effective21 (19.81)2 (20.0)23 (19.83)
      Effective43 (40.57)2 (20.0)45 (38.79)
      Very effective38 (35.85)1 (10.0)39 (33.62)
      Unsure2 (1.89)1 (10.0)3 (2.59)
      Bad moodNot effective0 (0.0) (n = 93)2 (22.22) (n = 9)0.0008*2 (1.96) (n = 102)
      Slightly effective11 (11.83)4 (44.44)15 (14.71)
      Effective31 (33.33)1 (11.11)32 (31.37)
      Very effective47 (50.54)2 (22.22)49 (48.04)
      Unsure4 (4.30)0 (0.0)4 (3.92)
      HeadacheNot effective3 (3.95) (n = 76)7 (46.67) (n = 15)<0.0001*10 (10.99) (n = 91)
      Slightly effective17 (22.37)2 (13.33)19 (20.88)
      Effective25 (32.89)0 (0.0)25 (27.47)
      Very effective27 (35.53)5 (33.33)32 (35.16)
      Unsure4 (5.26)1 (6.67)5 (5.49)
      Urination problems / difficultiesNot effective15 (30.61) (n = 49)5 (83.33) (n = 6)0.2494*20 (36.36) (n = 55)
      Slightly effective7 (14.29)0 (0.0)7 (12.73)
      Effective6 (12.24)0 (0.0)6 (10.91)
      Very effective3 (6.12)0 (0.0)3 (5.45)
      Unsure18 (36.73)1 (16.67)19 (34.55)
      To increase appetiteNot effective1 (2.13) (n = 47)0 (0.0) (n = 2)0.59181 (2.04) (n = 49)
      Slightly effective2 (4.26)0 (0.0)2 (4.08)
      Effective16 (34.04)0 (0.0)16 (32.65)
      Very effective28 (59.57)2 (100.0)30 (61.22)
      Unsure0 (0.0)0 (0.0)0 (0.0)
      Sexual problemsNot effective8 (19.51) (n = 41)2 (40.0) (n = 5)0.633610 (21.74) (n = 46)
      Slightly effective6 (14.63)1 (20.0)7 (15.22)
      Effective13 (31.71)1 (20.0)14 (30.43)
      Very effective9 (21.95)0 (0.0)9 (19.57)
      Unsure5 (12.20)1 (20.0)6 (13.04)
      ConstipationNot effective4 (18.18) (n = 22)3 (50.0) (n = 6)0.0938*7 (25.0) (n = 28)
      Slightly effective3 (13.64)2 (33.33)5 (17.86)
      Effective6 (27.27)0 (0.0)6 (21.43)
      Very effective2 (9.09)1 (16.67)3 (10.71)
      Unsure7 (31.82)0 (0.0)7 (25.0)
      ParalysisNot effective3 (17.65) (n = 17)0 (0.0) (n = 0)N/A3 (17.65) (n = 17)
      Slightly effective2 (11.76)0 (0.0)2 (11.76)
      Effective4 (23.53)0 (0.0)4 (23.53)
      Very effective4 (23.53)0 (0.0)4 (23.53)
      Unsure4 (23.53)0 (0.0)4 (23.53)
      Other causesNot effective0 (0.0) (n = 51)1 (25.0) (n = 4)0.08571 (1.82) (n = 55)
      Slightly effective8 (15.69)1 (25.0)9 (16.36)
      Effective23 (45.10)2 (50.0)25 (45.45)
      Very effective17 (33.33)0 (0.0)17 (30.91)
      Unsure3 (5.88)0 (0.0)3 (5.45)

      3.5 Adverse effects of medical cannabis

      Drowsiness (57.2%), feeling quiet/subdued (48.8%), difficulty concentrating (28.4%), balance problems (22.3%), and incoherent thoughts (17.7%) were the most reported adverse effects, however, less than 20% of current users that experienced any of these five effects reported experiencing them ‘a lot’ (Table 3). The remaining adverse effects were only reported by 2–16% of all current and former users and are much less common (Table 3). There were no significant differences in the ratings of the severity of any adverse effects reported by current and former users (Table 3).
      Table 3Reported Side Effects of Medical Cannabis. Comparisons made between current and former users were made using Chi-square and Fisher exact tests (*).
      SymptomCurrent User (n = 180)Former User (n = 35)P-valueTotal (n = 215)
      N (%)N (%)N (%)
      DrowsinessA little39 (37.14) (n = 105)5 (27.78) (n = 18)0.483344 (35.77) (n = 123)
      Moderately53 (50.48)9 (50.0)62 (50.41)
      A lot13 (12.38)4 (22.22)17 (13.82)
      Feeling quiet / subduedA little50 (55.56) (n = 90)5 (33.33) (n = 15)0.225055 (52.38) (n = 105)
      Moderately33 (36.67)9 (60.0)42 (40.0)
      A lot7 (7.78)1 (6.67)8 (7.62)
      Difficulty concentratingA little18 (38.30) (n = 47)4 (28.57) (n = 14)0.428322 (36.07) (n = 61)
      Moderately20 (42.55)5 (35.71)25 (40.98)
      A lot9 (19.15)5 (35.71)14 (22.95)
      Balance problemsA little25 (59.52) (n = 42)1 (16.67) (n = 6)0.1207*26 (54.17) (n = 48)
      Moderately10 (23.81)3 (50.0)13 (27.08)
      A lot7 (16.67)2 (33.33)9 (18.75)
      Incoherent thoughtsA little12 (44.44) (n = 27)4 (36.36) (n = 11)>0.999*16 (42.11) (n = 38)
      Moderately11 (40.74)5 (45.45)16 (42.11)
      A lot4 (14.81)2 (18.18)6 (15.79)
      Seeming remote / absentA little15 (51.72) (n = 29)1 (16.67) (n = 6)0.1258*16 (45.71) (n = 35)
      Moderately11 (37.93)3 (50.0)14 (40.0)
      A lot3 (10.34)2 (33.33)5 (14.29)
      Weakness in the bodyA little11 (47.83) (n = 23)6 (60.0) (n = 10)0.8676*17 (51.52) (n = 33)
      Moderately9 (39.13)3 (30.0)12 (36.36)
      A lot3 (13.04)1 (10.0)4 (12.12)
      HeadacheA little11 (55.0) (n = 20)2 (33.33) (n = 6)0.4876*13 (50.0) (n = 26)
      Moderately8 (40.0)3 (50.0)11 (42.31)
      A lot1 (5.0)1 (16.67)2 (7.69)
      NauseaA little11 (100.0) (n = 11)5 (71.43) (n = 7)0.1373*16 (88.89) (n = 18)
      Moderately0 (0.0)1 (14.29)1 (5.56)
      A lot0 (0.0)1 (14.29)1 (5.56)
      Financial problemsA little2 (12.50) (n = 16)0 (0.0) (n = 2)>0.999*2 (11.11) (n = 18)
      Moderately7 (43.75)1 (50.0)8 (44.44)
      A lot7 (43.75)1 (50.0)8 (44.44)
      Feeling persecutedA little3 (25.0) (n = 12)0 (0.0) (n = 2)>0.999*3 (21.43) (n = 14)
      Moderately6 (50.0)1 (50.0)7 (50.0)
      A lot3 (25.0)1 (50.0)4 (28.57)
      HallucinationsA little9 (90.0) (n = 10)3 (75.0) (n = 4)0.5055*12 (85.71) (n = 14)
      Moderately1 (10.0)1 (25.0)2 (14.29)
      A lot0 (0.0)0 (0.0)0 (0.0)
      SadnessA little4 (40.0) (n = 10)2 (66.67) (n = 3)0.5385*6 (46.15) (n = 13)
      Moderately4 (40.0)0 (0.0)4 (30.77)
      A lot2 (20.0)1 (33.33)3 (23.08)
      Problems at workA little3 (42.86) (n = 7)0 (0.0) (n = 1)>0.999*3 (37.50) (n = 8)
      Moderately2 (28.57)1 (100.0)3 (37.50)
      A lot2 (28.57)0 (0.0)2 (25.0)
      Risky behaviorA little2 (50.0) (n = 4)1 (100.0) (n = 1)>0.999*3 (60.0) (n = 5)
      Moderately2 (50.0)0 (0.0)2 (40.0)
      A lot0 (0.0)0 (0.0)0 (0.0)
      Other consequencesA little3 (60.0) (n = 5)1 (100.0) (n = 1)>0.999*4 (66.67) (n = 6)
      Moderately1 (20.0)0 (0.0)1 (16.67)
      A lot1 (20.0)0 (0.0)1 (16.67)

      4. Discussion

      The legalization of recreational cannabis in Canada in 2018 may have increased its accessibility to people with MS. As such, the study of the prevalence of use and the symptoms for which cannabis is used is apropos. Indeed, we found that about two-thirds of participants reported having used medical cannabis to manage their MS symptoms, with those who have tried medical cannabis living with a greater disease burden than nonusers. Users of cannabis reported moderately to high effectiveness in treating spasticity, pain, sleep disorders, mood, stress and appetite stimulation, and that adverse effects, including drowsiness, feeling quiet/subdued, and difficulty concentrating, are not generally severe. These patient-reported findings may inform future research into the efficacy of cannabis to treat the symptoms of MS.
      Almost 80% of our participants were female (Table 1), consistent with reported gender differences in the prevalence of MS (
      • Koch-Henriksen N.
      • Sørensen P.S.
      The changing demographic pattern of multiple sclerosis epidemiology.
      ) and with other MS studies (
      • Page S.A.
      • Verhoef M.J.
      • Stebbins R.A.
      • Metz L.M.
      • Levy J.C.
      Cannabis use as described by people with multiple sclerosis.
      ;
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ;
      • Clark A.J.
      • Ware M.A.
      • Yazer E.
      • Murray T.J.
      Lynch ME. Patterns of cannabis use among patients with multiple sclerosis.
      ). The average age of participants, around 45 years, and the relatively higher proportion of RRMS compared to other MS phenotypes (Table 1) is consistent with the relative prevalence of different types of MS (
      • Yamout B.I.
      • Alroughani R.
      Multiple sclerosis.
      ;
      • Dobson R.
      • Giovannoni G.
      Multiple sclerosis – a review.
      ) and also concurs with other studies (
      • Page S.A.
      • Verhoef M.J.
      • Stebbins R.A.
      • Metz L.M.
      • Levy J.C.
      Cannabis use as described by people with multiple sclerosis.
      ;
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ). Our findings are consistent with those of Gustavsen et al. in Denmark (
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ), whose study population was comparable to ours in terms of gender distribution, age, duration of MS, PDDS scores, and clinical diagnosis. They reported that 48.7% of respondents to their survey (upon which ours was based) had tried cannabis, although it was not specified whether it was for medical purposes or not (
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ). Their findings surrounding beneficial and adverse effects were also similar: cannabis was highly rated in treating spasticity, pain, and sleep problems, with drowsiness and feeling subdued being the most reported adverse effects (
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ). A key reason why our study found that a greater proportion of users that had tried medical cannabis might be that at the time that Gustavsen et al. conducted their investigation, a pilot program allowing physicians to prescribe medical cannabis was still in its infancy and cannabis was otherwise illegal (
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ; ). Recreational cannabis is legal in Canada and therefore more readily available to people living with MS, which could account for our finding that a greater proportion of Canadians with MS had tried medical cannabis. Overall, the perceived beneficial and adverse effects are similar between studies, emphasizing the therapeutic potential of medical cannabis. However, these potential effects must be tested in controlled studies.
      Our findings are in line with those of Page et al. (
      • Page S.A.
      • Verhoef M.J.
      • Stebbins R.A.
      • Metz L.M.
      • Levy J.C.
      Cannabis use as described by people with multiple sclerosis.
      ) and Clark et al. (
      • Clark A.J.
      • Ware M.A.
      • Yazer E.
      • Murray T.J.
      Lynch ME. Patterns of cannabis use among patients with multiple sclerosis.
      ), where medical cannabis users reported that it was generally effective in treating stress, anxiety, pain, sleep problems, spasticity, and poor mood (
      • Page S.A.
      • Verhoef M.J.
      • Stebbins R.A.
      • Metz L.M.
      • Levy J.C.
      Cannabis use as described by people with multiple sclerosis.
      ;
      • Clark A.J.
      • Ware M.A.
      • Yazer E.
      • Murray T.J.
      Lynch ME. Patterns of cannabis use among patients with multiple sclerosis.
      ). Only one of these studies examined adverse effects, with just over 25% of medical cannabis users reporting moderate to strong adverse effects (
      • Clark A.J.
      • Ware M.A.
      • Yazer E.
      • Murray T.J.
      Lynch ME. Patterns of cannabis use among patients with multiple sclerosis.
      ), which is consistent with our findings. The other study also looked at how cannabis was consumed, with most participants smoking it in whole-plant or hash form and a smaller contingent eating or drinking it in the form of ingestible products (
      • Page S.A.
      • Verhoef M.J.
      • Stebbins R.A.
      • Metz L.M.
      • Levy J.C.
      Cannabis use as described by people with multiple sclerosis.
      ). However, participants in both studies who had tried medical cannabis only represented 14% (
      • Clark A.J.
      • Ware M.A.
      • Yazer E.
      • Murray T.J.
      Lynch ME. Patterns of cannabis use among patients with multiple sclerosis.
      ) and 16% (
      • Page S.A.
      • Verhoef M.J.
      • Stebbins R.A.
      • Metz L.M.
      • Levy J.C.
      Cannabis use as described by people with multiple sclerosis.
      ) of all participants, which, given when these studies were conducted, likely reflects that medical cannabis had only been legal for a few years prior (
      • Cox C.
      The Canadian Cannabis Act legalizes and regulates recreational cannabis use in 2018.
      ), and it would be nearly 15 more before it would be legal recreationally.
      Our results also indicate that those who have tried medical cannabis were more likely to have learned about it through their social circle or on their own, rather than from a healthcare provider. This could be because not all healthcare providers are knowledgeable about the potential benefits of medical cannabis, may not be comfortable recommending it based on the lack of high-quality evidence and concerns surrounding possible addiction and other adverse effects (
      • Ko G.D.
      • Bober S.L.
      • Mindra S.
      • Moreau J.M.
      Medical cannabis – the Canadian perspective.
      ), or may not be licensed to prescribe it.
      Many people with MS learn about cannabis on their own, which underscores a need for evidence-based resources to be readily available and updated to inform those exploring medical cannabis use for MS and to encourage them to engage in discussions with their healthcare team. As more research becomes available and evidence becomes stronger, updating and increasing the availability of such resources should be a priority.
      Our results also show that the adverse effects that people report were of mild to moderate severity and generally tolerable, no serious adverse effects (e.g., psychosis, falls, arrythmias) were reported, and that adverse effects are not the main reason that people cease to use medical cannabis. Cost, accessibility, and a lack of effectiveness were the main reasons former users cite for stopping. This is encouraging, as it is in line with the findings of a 2018 systematic review (
      • Nielsen S.
      • Germanos R.
      • Weier M.
      • Pollard J.
      • Degenhardt L.
      • Hall W.
      • Buckley N.
      • Farrell M.
      The use of cannabis and cannabinoids in treating symptoms of multiple sclerosis: a systematic review of reviews.
      ), which reported that most adverse effects were described mostly as mild or moderate. These findings position medical cannabis as a potentially attractive option to both physicians considering prescribing it and prospective medical cannabis users, quelling concerns surrounding the potential for severe adverse effects.
      Although our results are encouraging and highlight the apparent benefits of medical cannabis for the majority of those who use it to manage symptoms of MS, further study, both basic and clinical, is required to fully elucidate the mechanisms behind medical cannabis’ amelioration of a variety of symptoms. Furthermore, more clinical trials are needed to examine the effects and safety of whole-plant cannabis in MS, as we and others have shown that it is a commonly used preparation by this population (
      • Page S.A.
      • Verhoef M.J.
      • Stebbins R.A.
      • Metz L.M.
      • Levy J.C.
      Cannabis use as described by people with multiple sclerosis.
      ;
      • Gustavsen S.
      • Søndergaard H.B.
      • Andresen S.R.
      • Magyari M.
      • Sørensen P.S.
      • Sellebjerg F.
      • Oturai A.B.
      Illegal cannabis use is common among Danes with multiple sclerosis.
      ;
      • Clark A.J.
      • Ware M.A.
      • Yazer E.
      • Murray T.J.
      Lynch ME. Patterns of cannabis use among patients with multiple sclerosis.
      ) and there is a distinct lack of data examining it. Finally, more research is needed into the various modalities of taking cannabis, and whether there are differences in efficacy of the cannabis products and adverse effects.

      4.1 Limitations and strengths

      Our survey was based on a previous study and included validated quality of life instruments, the PDDS and MSQOL-54, which strengthened our study design. The use of these instruments helps support our claim that individuals who have more severe MS are more likely to use medical cannabis products. Another strength of this study is its ability to reach and capture the broadest possible cross-section of people with MS by minimizing exclusion criteria and opening it up to national participation through the MS Society of Canada. This allowed us to maximize our sample size and the amount of data we could collect while working within the restrictions imposed on our study design by the COVID-19 pandemic.
      Although the survey was not just sent to a single, specific group of potential participants and was advertised over social media, our study is still likely subject to response bias; that is, those who were interested in cannabis may have been more likely to click on the link and complete the survey when it showed up on their social media feed. Since our sampling method was through electronic means, this might limit responses to those who are more technologically literate. Consequently, it is difficult to assert that our sample is truly representative of the whole Canadian MS population. Additionally, as the data is self-reported, there may also have been a degree of over- or under-reporting regarding the efficacy and adverse effects of medical cannabis, although our findings were consistent with the literature. However, based on the data that we aimed to collect and the restrictions that we needed to work around, the method that we employed was likely the most sensible option.
      Despite our limitations, the information that we gained from the individual groups of participants (nonusers, current users, and former users) is still valuable and consistent with what has been reported in the literature when examining the effects of cannabis in people with MS. It also gives us an idea of what cannabis products people with MS are using, where they are getting it, and where they learned about it. To our knowledge, this has not been examined in Canada for several years since before cannabis was legalized, and not to the degree of detail that we report. While other studies may have collected more data concerning participant characteristics (marital status, education level, income, etc.), we felt that this was not necessary for our purposes, and additional subgroup analysis based on these characteristics was beyond the scope of our objectives.
      In conclusion, we have demonstrated that nearly two-thirds of people with MS in Canada have tried medical cannabis at least once, and three-quarters of these individuals continue to use cannabis to manage their symptoms currently. Our results highlight the need for further research into the mechanisms underlying the effects of cannabis in treating MS symptoms and randomized controlled trials of cannabis and derivative products. Finally, this study underscores the need for comprehensive, accessible, objective, evidence-based resources outlining the benefits and drawbacks of medical cannabis to be readily available both to primary healthcare providers and to the public to increase awareness of medical cannabis and to reduce the social stigma that continues to surround it.

      CRediT authorship contribution statement

      Talia M Santarossa: Methodology, Investigation, Writing – original draft, Writing – review & editing, Visualization. Randy So: Conceptualization, Methodology, Writing – review & editing. Dr Penelope Smyth: Funding acquisition, Writing – review & editing. Dr Stefan Gustavsen: Methodology, Writing – review & editing. Dr Ross T Tsuyuki: Supervision, Funding acquisition, Writing – review & editing.

      Declarations of Interest

      TS and RS have nothing to declare. PS has received consultant and advisory fees from Novartis Pharmaceuticals, Roche Canada, STEDT, Sanofi-Genzyme, EMD Serono Canada, Biogen-Idec Canada, Alexion Pharmaceuticals and Bristol-Myers-Squibb Pharmaceuticals. She has engaged in research as a co-investigator funded by CIHR, Biogen Pharmaceuticals, and the MS Society of Canada. SG has received support for congress participation from Merck and has worked at a private pain clinic, Clinic Horsted, with expertise in cannabis treatment. RT has received investigator-initiated research funding from Merck, Pfizer, AstraZeneca, Sanofi, and Servier. He is the Editor-In-Chief of the Canadian Pharmacists Journal and a medical consultant to Shoppers Drug Mart/Loblaws and Emergent BioSolutions.

      Acknowledgements

      The authors wish to thank Dr. Yazid Al Hamarneh for contributing to the initial study design and for reviewing the manuscript, Dr. Sherry Woitte for providing feedback on the survey instrument design, and Lily Yushko and Bo Pan at EPICORE Centre for their support in data management and statistical analyses. The authors would also like to thank the University Hospital Foundation at the University of Alberta for graciously funding this study.

      Funding

      This study is funded by the University Hospital Foundation at the University of Alberta (RES0013590).

      References

        • Cox C.
        The Canadian Cannabis Act legalizes and regulates recreational cannabis use in 2018.
        Health Policy. 2018; 122: 205-209https://doi.org/10.1016/j.healthpol.2018.01.009
        • Page S.A.
        • Verhoef M.J.
        • Stebbins R.A.
        • Metz L.M.
        • Levy J.C.
        Cannabis use as described by people with multiple sclerosis.
        Can. J. Neurol. Sci. 2003; 30: 201-205https://doi.org/10.1017/S0317167100002584
        • Gustavsen S.
        • Søndergaard H.B.
        • Andresen S.R.
        • Magyari M.
        • Sørensen P.S.
        • Sellebjerg F.
        • Oturai A.B.
        Illegal cannabis use is common among Danes with multiple sclerosis.
        Mult. Scler. Relat. Disor. 2019; 33: 5-12https://doi.org/10.1016/j.msard.2019.05.008
        • Nielsen S.
        • Germanos R.
        • Weier M.
        • Pollard J.
        • Degenhardt L.
        • Hall W.
        • Buckley N.
        • Farrell M.
        The use of cannabis and cannabinoids in treating symptoms of multiple sclerosis: a systematic review of reviews.
        Curr. Neurol. Neurosci. Rep. 2018; 18: 8https://doi.org/10.1007/s11910-018-0814-x
        • Russo E.B.
        Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects.
        Br. J. Pharmacol. 2011; 163: 1344-1364https://doi.org/10.1111/j.1476-5381.2011.01238.x
        • Koppel B.S.
        • Brust J.C.M.
        • Fife T.
        • Bronstein J.
        • Youssof S.
        • Gronseth G.
        • Gloss D.
        Systematic review: efficacy and safety of medical marijuana in selected neurologic disorders.
        Neurology. 2014; 82: 1556-1563
        • Yadav V.
        • Bever C.
        • Bowen J.
        • Bowling A.
        • Weinstock-Guttman B.
        • Cameron M.
        • Bourdette D.
        • Gronseth G.S.
        • Narayanaswami P.
        Summary of evidence-based guideline: complementary and alternative medicine in multiple sclerosis.
        Neurology. 2014; 82: 1083-1092https://doi.org/10.1212/WNL.0000000000000250
        • Suryadevara U.
        • Bruijnzeel D.M.
        • Nuthi M.
        • Jagnarine DA
        • Tandon R.
        • Bruijnzeel A.W.
        Pros and cons of medical cannabis use by people with chronic brain disorders.
        Curr. Neuropharmacol. 2017; 15: 800-814https://doi.org/10.2174/1570159x14666161101095325
        • Honarmand K.
        • Tierney M.C.
        • O’Connor P.
        • Feinstein A.
        Effects of cannabis on cognitive function in patients with multiple sclerosis.
        Neurology. 2011; 76: 1153-1160https://doi.org/10.1212/WNL.0b013e318212ab0c
        • Feinstein A.
        • Banwell E.
        • Pavisian B.
        What to make of cannabis and cognition in MS: in search of clarity amidst the haze.
        Mult. Scler. 2015; 21: 1755-1760https://doi.org/10.1177/1352458515607652
        • Patel V.P.
        • Feinstein A.
        Cannabis and cognitive functioning in multiple sclerosis: the role of gender.
        Mult. Scler. J. 2017; 3https://doi.org/10.1177/2055217317713027
        • Clark A.J.
        • Ware M.A.
        • Yazer E.
        • Murray T.J.
        Lynch ME. Patterns of cannabis use among patients with multiple sclerosis.
        Neurology. 2004; 62: 2098-2100https://doi.org/10.1212/01.WNL.0000127707.07621.72
        • Vickrey B.G.
        • Hays R.D.
        • Harooni R.
        • Myers L.W.
        • Ellison G.W.
        A health-related quality of life measure for multiple sclerosis.
        Qual. Life Res. 1995; 4: 187-206https://doi.org/10.1007/BF02260859
        • Learmonth Y.C.
        • Motl R.W.
        • Sandroff B.M.
        • Pula J.H.
        Cadavid D. Validation of patient determined disease steps (PDDS) scale scores in persons with multiple sclerosis.
        BMC Neurol. 2013; 13: 37https://doi.org/10.1186/1471-2377-13-37
        • Gilmour H.
        • Ramage-Morin P.L.
        • Wong S.L.
        Multiple sclerosis: prevalence and impact.
        Health Rep. 2018; 29: 3-8
        • Smyth P.
        • Watson K.E.
        • Tsuyuki R.T.
        Measuring the Effects of Nurse-Practitioner (NP) - Led Care on Depression and Anxiety Levels in People with Multiple Sclerosis : a Study Protocol for a Randomized Controlled Trial Trial Registration.
        PREPRINT (Version 1). 2022; https://doi.org/10.21203/rs.3.rs-537085/v1
        • Koch-Henriksen N.
        • Sørensen P.S.
        The changing demographic pattern of multiple sclerosis epidemiology.
        Lancet Neurol. 2010; 9: 520-532https://doi.org/10.1016/S1474-4422(10)70064-8
        • Yamout B.I.
        • Alroughani R.
        Multiple sclerosis.
        Semin. Neurol. 2018; 38: 212-225
        • Dobson R.
        • Giovannoni G.
        Multiple sclerosis – a review.
        Eur. J. Neurol. 2019; 26: 27-40https://doi.org/10.1111/ene.13819
        • Danish Medicines Agency
        Medicinal Cannabis Pilot Programme.
        2019 ([accessed 2021 May 3])
        • Ko G.D.
        • Bober S.L.
        • Mindra S.
        • Moreau J.M.
        Medical cannabis – the Canadian perspective.
        J. Pain Res. 2016; 9: 735-744https://doi.org/10.2147/JPR.S98182