We observed that although primary care healthcare providers in a state with an established program generally believe that medical cannabis is a legitimate medical therapy and safer than illegal cannabis, significant knowledge gaps existed about effectiveness related to state designated qualifying medical conditions and one-half were not prepared to answer patient questions about it. Most providers indicated they were aware that some of their patients were using cannabis illegally to treat medical conditions, but few believed that medical cannabis improved patient quality of life domains. A significant proportion of providers endorsed that medical cannabis had potential interactions with medical therapies. Most providers were interested in learning more about medical cannabis.

Only three of thirteen Minnesota state designated qualifying medical conditions had a majority of providers endorsing that medical cannabis was an effective management strategy for them. However, more than one-half of providers believed that medical cannabis was effective for the management of nausea/vomiting, muscle spasms including those characteristic of M.S., and pain, three conditions for which the best evidence exists [6]. Knowledge gaps in the literature exist regarding the effectiveness of medical cannabis for different medical conditions, and data available supporting the potential efficacy of medical cannabis for state designated qualifying medical conditions varies substantially. For example, available data suggests cannabinoid use is associated with only short-term reductions in intraocular pressure [16]; the National Academies of Sciences, Engineering, and Medicine (NASEM) concluded that limited evidence suggests that they are ineffective for the treatment of glaucoma [6], one of the most common qualifying medical conditions among state medical cannabis programs [17]. States interested in maintaining medical cannabis laws for medical indications could consider a more evidence-based approach when adding additional qualifying conditions. This approach may increase the perceived legitimacy of medical cannabis for qualifying conditions among certifying clinicians and increase the likelihood that providers would consider medical cannabis as part of a comprehensive treatment strategy.

Most providers did not endorse that they believed medical cannabis improved aspects of patient quality of life (QOL). Systematic reviews have demonstrated that cannabinoids improve QOL among patients taking them for chronic neuropathic pain [18]. This particular review included studies evaluating dronabinol (THC), nabilone (THC biosimilar), and nabiximols (THC and cannabidiol, CBD). Such information is informative for both patients and providers in Minnesota as products available through the state program consist exclusively of THC and/or CBD. However, exceptionally few studies on medical cannabis have collected QOL measures [6] making it difficult for providers to be informed about potential benefit in these domains. Researchers should be encouraged to include quality of life measures, such as the SF-36 [19], especially in prospective studies as this questionnaire is publicly-available, validated, and easily collected. Patient QOL considerations have significant impact on provider clinical decision-making [20]. Adding QOL measures to an assessment battery along with the outcomes of interest (e.g., pain and spasticity) should not be viewed as overly burdensome and will critically advance the science.

We observed that over one-third of providers believed that medical cannabis has significant interactions with medical therapies. Providers need to be informed of potential interactions between medications they prescribe and products obtained from state dispensaries. Even when products contain only THC and CBD as constituents, providers and allied health professionals have little understanding of the concentration of these cannabinoids in the formulations patient receive from the state dispensary and this information is not loaded into electronic medical records. As a result, software automatically flagging drug interactions cannot assist prescribers. To address this concern, clinicians may stop medical cannabis in order to avoid these interactions when starting new medications, a problem that may be exacerbated in states making available smoked cannabis which contains over 100 phytocannabinoids (i.e., natural plant products) [21]. Although the evidence for significant drug interactions with THC and CBD is rare, THC and CBD are metabolized by CYP1A2, CYP2C9, CYP2C19, and CYP3A4 and serum concentrations of these molecules may theoretically increase with medications that inhibit or induce these enzymes [22]. Greater information sharing between dispensaries, patients and providers regarding the dosing of medical cannabis and the relative concentrations of medical cannabis constituent components present opportunities to improve patient safety.

We observed that 50% providers were not ready or did not want to answer patient questions about medical cannabis. This is consistent with previous research among US residents and fellows observing that only 35.3% of respondents felt ready to answer patient questions about cannabis [23]. Reassuringly, we found that over three-quarters of providers were interested in learning more about medical cannabis. Previous surveys have reported a strong desire among providers to obtain and support additional education on medical cannabis [12, 24]. Given the expansion of medical cannabis in the US, medical education and continuing medical education needs to include curricula on cannabinoids or these profound knowledge gaps will put patients and providers at risk.

The strengths of our survey include that it was conducted among primary care providers in a large, integrated healthcare system in a state where medical cannabis laws have been present for two years, we assessed beliefs about the effectiveness of medical cannabis for state designated qualifying conditions, and we observed a high response rate. Our study is limited by sample size and generalizability as questions were referential to the Minnesota state cannabis program, but this program is very similar to other state programs.