In this study, we examined the substitution of medical cannabis for pharmaceuticals, as well as doctor-patient communication patterns about substitution, among Canadian medical cannabis dispensary patients. As hypothesized, participants rated PCPs as being quite knowledgeable of cannabis (“good” on average), and the majority received PCP authorization for medical cannabis. However, our hypothesis about substitution disclosure was not confirmed, as many participants either did not communicate or delayed communicating for 6 months or more with their PCP about substituting cannabis for other medications or substances, such as opioids, alcohol, and tobacco (Boehnke et al. 2021). Overall, results suggest uneven integration between medical cannabis and mainstream healthcare, evidenced by limited doctor-patient communication concerning the substitution of cannabis for pharmaceuticals.

Given that Canada has a more mature regulatory framework than Michigan, it follows that comparatively more patients in Canada obtain licensure from their PCP (62.7% vs. 14%), and Canadian patients generally report that their PCP has better knowledge of medical cannabis (60.7% vs. 39% rated as “good” to “excellent”) and are more confident of their PCP’s ability to integrate cannabis into their treatment (48.2% vs. 18.9% rated as “very confident” or “completely confident”) (Boehnke et al. 2021). Indeed, in Canada, cannabis is legal medically and recreationally at a federal level versus in the USA, where cannabis is still classified as a Schedule I drug federally with varying laws governing its use in each state (Boehnke et al. 2019b).

These findings add to the medical cannabis and substitution literature (Boehnke et al. 2016, 2019a; Bradford and Bradford 2016, 2017; Bradford et al. 2018; Lucas et al. 2016, 2019; Reiman et al. 2017; Piper et al. 2017a; Corroon Jr. et al. 2017) and confirm Michigan results that substitution often occurs without physician oversight (Boehnke et al. 2021). Whereas substitution can have a beneficial impact, for instance by decreasing opioid use when cannabis is used as part of a harm reduction strategy (Lucas 2017), proceeding without physician involvement has associated risks. Indeed, adverse effects, such as illness recurrence, could result if patients substitute cannabis for disease-modifying drugs (Boehnke et al. 2021). Furthermore, open communication between patient and provider about medical cannabis could facilitate information sharing, as well as foster the therapeutic alliance and enable shared decision-making. Indeed, consistent with our study in Michigan (Boehnke et al. 2021), participants whose PCP authorized medical cannabis perceived their PCP to have better medical cannabis knowledge and greater confidence in their ability to integrate cannabis into treatment. In addition, a recent survey reported that 24% of participants considered health professionals to be their most influential information sources about cannabis, and these participants were less likely to believe false claims about cannabis (Ishida et al. 2020). Lastly, a qualitative study of older adults showed that most participants wanted to discuss cannabis with their physicians despite expressing concerns about provider openness and knowledge about medical cannabis (Bobitt et al. 2019). These studies highlight the importance of the doctor-patient relationship in maximizing benefits and minimizing risks associated with medical cannabis use.

Our results showed that older and female participants were more likely to disclose cannabis substitution. Polypharmacy is prevalent among older individuals (Dagli and Sharma 2014); thus, concerns surrounding drug-drug interactions may prompt older individuals to discuss medication use with their physicians. Furthermore, older individuals have more health issues and visit the doctor more frequently (Institute of Medicine 2008), providing greater opportunity for conversation. Additionally, the elderly may be more susceptible to adverse effects from THC (Kaufmann et al. 2020) and may be more cautious in guiding their own use. Women have overall higher healthcare utilization than men (Bertakis et al. 2000; Ladwig et al. 2000) and are more likely to use complementary and alternative medicine (Zhang et al. 2015) both of which may increase the likelihood of speaking with providers about medical cannabis use. Furthermore, men generally have a higher prevalence of cannabis use (Wall et al. 2019; Compton et al. 2016) and may feel less need to disclose due to their knowledge gleaned from historical use. However, this reporting difference based on gender is intriguing in light of a recent survey study showing that women in Illinois felt less supported by specialist providers in their use of medical cannabis compared with male respondents (Bruce et al. 2021). Additionally, stigma regarding cannabis use may be exacerbated for females with children (Dahl and Sandberg 2015), with some women expressing difficulty reconciling internal and external expectations of motherhood with cannabis use (Dahl and Sandberg 2015; Hathaway et al. 2011). More research on the interface between gender and substitution is needed to better contextualize these findings.

The reason for the communication gap about medical cannabis in healthcare is likely multifaceted, creating barriers for both patients and physicians to open lines of communication. One explanation for the delay in communication about medical cannabis between patient and provider could be due to a lack of regular PCP visits. While this may be a contributing factor, there are other important considerations. For instance, in addition to patient concerns about PCP knowledge and ability to integrate medical cannabis into treatment, cannabis’s historical criminalization has caused patients to fear stigma, legal, or professional ramifications—all of which may discourage open communication about medical cannabis (Boehnke et al. 2021; Piper et al. 2017b; Bottorff et al. 2013; Lau et al. 2015a, b). A recent survey study of cancer patients in Italy showed that although 34% of respondents had considered using medical cannabis, only 11% considered contacting their physicians to obtain more information (Cortellini et al. 2019). While 81% of respondents had heard about medical cannabis, only 2% reported hearing about it from their physician (Cortellini et al. 2019). Likewise, many physicians remain reluctant to use medical cannabis in clinical practice. A recent meta-analysis including data from five countries with different medical cannabis regulatory systems showed that although physicians experience a substantial rate of patients inquiring about medical cannabis, there is a wide variability in their openness to prescribing, authorizing, and/or providing it (Ronne et al. 2021). Beliefs about medical cannabis appear to depend in part on experience, with providers who have more experience authorizing medical cannabis believing more in its beneficial effects and feeling less concerned about its adverse effects than those with no experience (Ronne et al. 2021). In addition, provider knowledge about medical cannabis also appears to affect provider attitudes. A recent survey study of Italian medical oncologists and palliative care physicians showed that while only a minority (14%) of respondents could name the law governing medical cannabis use, this knowledge correlated with a greater probability of prescription (Filetti et al. 2021). Furthermore, there was a gap in respondent knowledge, with a significant minority (31%) of respondents reporting not having enough information to distinguish the side effect profiles of medical cannabis and opioids and only 9 of 140 respondents reporting medical cannabis side effects in their patients (Filetti et al. 2021).

Notably, this study extends beyond prior work to consider the role of secondary care providers. Over one-third of current participants approached secondary care providers working in specialized medical cannabis clinics, whom they rated higher on measures of knowledge and ability to integrate cannabis into treatment. Although this greater perceived knowledge is unsurprising given the specialization, this highlights an area where continued improvement is needed, especially as providers in medical cannabis clinics may potentially have a higher degree of conflicts of interest. Ideally, even if patients sought advice on cannabis use from a secondary provider, patients would obtain a recommendation from their PCPs, who are presumably more familiar with patient medical histories, have established relationships, and have continued involvement in their healthcare (Bobitt et al. 2019). In addition, without continuous visibility on important treatment changes undertaken by their patients, including changes in prescription drug use, providing appropriate care becomes more challenging. Further understanding of the secondary provider relationship is also needed, as 71.2% (n = 695) of participants reported no continued involvement of their secondary provider in their medical care, suggesting that these participants still may need ongoing support in optimizing cannabis use.

While Canada has a longstanding medical cannabis program, our results indicate that gaps persist regarding its integration into mainstream healthcare systems. Increasing provider education concerning medical cannabis could help address this gap. Indeed, a small minority of medical schools (9%) include medical cannabis curriculum content (Evanoff et al. 2017). This lack of formal education combined with the lack of robust cannabis clinical trials literature to guide physician recommendations creates a situation in which patients are largely on their own to make challenging decisions. However, by using harm-reduction and benefit-maximization strategies, physicians can help guide safe patient use of medical cannabis. Using a combination of administration routes, as well as a “low and slow” dosing technique, for instance, can help physicians tailor their treatment plans to patient needs (Boehnke and Clauw 2019; MacCallum and Russo 2018). Education about these principles, as well as clinical experience applying them to clinical care, would improve physicians’ abilities to engage in shared decision making with their patients about medical cannabis (Boehnke et al. 2021; Ronne et al. 2021).