In this study, we report the results of the first prospective cohort study to survey cannabis use amongst patients with IBD following the legalization of cannabis in Canada. The Cannabis Act was new legislation that was passed in 2018 with the aims of providing access to a quality-controlled supply of cannabis, displacing the illegal cannabis market and preventing youth from accessing cannabis. The Act allows any person over the age of 18 to possess up to 30 grams of legal cannabis and grow up to 4 plants for personal use. At the time the Act was passed, it made Canada one of four countries to legalize recreational use of cannabis. Indeed, the United States Drug Enforcement Administration in contrast continues to list cannabis as a Schedule 1 drug alongside drugs such as heroin. Reasons often cited for this include that approximately 1 in 10 people who experiment with cannabis will become addicted.¹⁴ Additionally, chronic daily use of cannabis is associated with impaired respiratory function, psychotic symptoms, impaired educational attainment, and subtle cognitive impairment.¹⁵

Consistent with previous reports, we found that 53% of patients with IBD had used cannabis in their lifetime.^4,16 In this study, however, we found that rates of recent cannabis use were more than twice that previously reported in studies from 2006 (CD 41% vs 15.9%; UC 31% vs 11.6%).⁴ The Cannabis Act has likely led to increased reporting of cannabis use by boosting access and lowering the stigma associated with cannabis. Indeed, cannabis use in Canadians increased from 14.0% to 17.5% in the first year after legalization.¹⁷ Our findings that 51% of responders started using cannabis only in the preceding 3 years is consistent with legalization increasing its adoption. Interestingly, the rates of recent cannabis use in our study were similar to a 2017 survey study of British Columbia patients with IBD done prior to cannabis legalization (50.6% CD and 35.7% UC).¹⁶ While the rates reported in that previous study were high, British Columbia was well known to have a higher rate of cannabis use when compared to the national Canadian average even prior to legalization. In fact, according to the 2017 Canadian Tobacco, Alcohol, and Drugs Survey, 23.4% of British Columbians had reported using cannabis in the previous year versus only 14% of Ontario residents.¹⁷ We acknowledge that our study was conducted during the COVID-19 pandemic when Canadians faced unprecedented financial and social upheaval. Despite these stressors, the percentage of individuals using cannabis in Ontario increased marginally from 23% in 2020 to 24% in 2021.¹⁸ Thus, the pandemic alone is not likely to have significantly contributed to the large increase in cannabis consumption observed during our study.

In the present study, 30% of survey responders stated they used cannabis to relieve their gastrointestinal symptoms, while others consumed cannabis for reasons applicable to the general public such as recreation. Active users of cannabis also reported more abdominal pain, poor appetite, and flatulence, coinciding with lower SIBDQ scores indicating a lower quality of life when compared to non-users of cannabis. Subgroup analyses revealed that individuals with IC, but not CD or UC, reported lower SIBDQ scores with recent cannabis use. The UC group, however, trended towards lower SIBDQ scores. Pi et al. similarly found lower SIBDQ scores in patients with UC, but not in patients with CD who used cannabis.¹⁶ Our findings point to a possible difference in the mechanism of disease between CD and UC. The exact mechanism by which cannabis exerts its action on disease activity, however, is currently unknown. A recent double-blind, randomized, placebo-controlled trial of 32 patients with UC found that daily inhalation of THC-predominant cannabis did not alter endoscopic Mayo scores.¹⁹ Other markers of disease activity including serum C-reactive protein levels, hemoglobin, or fecal calprotectin also did not differ between treatment arms. Similarly, other studies have also failed to demonstrate any impact of cannabis on empiric markers of IBD severity.²⁰ In contrast, a trial by Naftali et al., reported an improvement in quality of life scores with cannabis use.¹⁹ The discrepancy between our results and that reported by Naftali et al., likely stems from their use of the Short Form Health Survey, a 36-question survey designed to compare generic illness and measure quality of life. In the present study, we used the SIBDQ, a validated IBD-specific questionnaire.²¹ Thus, the improved quality of life scores observed by Naftali et al. may be attributable to the psychoactive and euphoric effects associated with daily cannabis use.

Cannabis may also be associated with lower SIBDQ scores as a result of higher use amongst those patients with more severe diseases. Indeed, we found a difference in SIBDQ scores in patients with IC. Patients in this group were more likely to be recently diagnosed and have received no IBD-specific therapy. This IBD group likely relied on cannabis to alleviate their symptoms in the absence of adequate medical therapy. In fact, 30 percent of our survey responders reported using cannabis primarily to alleviate their GI symptoms despite numerous studies showing no benefit.⁶ Complementary and alternative medicines such as herbs, acupuncture, homeopathic medicines, and meditation are commonly used by 30-50% of patients with IBD.²² Consistent with this, predictors of CAM use in IBD have previously been reported to include experiencing side effects or dissatisfaction with conventional medication, extra-intestinal manifestations or long-term progression of disease, and prolonged steroid use.^23–25 Similarly, predictors of cannabis use include previous abdominal surgery, use of pain medication, and use of other complementary and alternative medicines.⁴ Thus, it is reasonable to speculate that individuals with increased disease burden use cannabis when other therapies fail them. While many of our survey responders believed cannabis is safe and innocuous, its use has been reported to be associated with a higher risk for surgery in patients with CD.⁸

This study clearly highlights the prevalence of cannabis use amongst patients with IBD and its impact on these patients, particularly in the post-legalization era. We acknowledge several limitations of the current study, however, including the reliance on self-reported data, which could introduce recall bias and affect the accuracy of reported cannabis use and symptom severity. The cross-sectional study design also limits our ability to infer causal relationships between cannabis use and IBD outcomes. Moreover, our study sample was drawn from a specific geographical area, healthcare setting, and largely Caucasian population, potentially limiting the generalizability of the findings to other populations. These limitations highlight the need for further research, including longitudinal and randomized controlled trials, to better understand the impacts of cannabis use on IBD. Nevertheless, our study underscores the need for physicians caring for patients with IBD to be aware that cannabis use has significantly increased following its legalization in Canada, and that its use is associated with worse disease outcomes. This association does not necessarily indicate causality but does suggest that the underlying severity of IBD could impact cannabis use or vice-versa.

Thus, physicians should always inquire about cannabis use and look for opportunities to optimize their patients’ symptoms with proven therapies. Additional high-quality randomized controlled studies may be warranted to evaluate the potential benefits or harm of cannabis in IBD management.