Based on recent epidemiological data and current public perceptions of safety of cannabis use in general, we had hypothesized a 10% current usage among patients with infertility. In our study, which included a population of patients with infertility attending a metropolitan academic hospital-based fertility clinic, we found that the self-reported prevalence of cannabis use in the last year is 13%. Given that patients are not typically referred to a fertility clinic until they have been trying to conceive for at least 1 year, one would expect patients open to reducing cannabis use would have already reduced any modifiable behaviours that are perceived to have a negative impact on fertility prior to being referred for fertility treatment. This suggests that people who continue to use cannabis recreationally do not perceive any negative impact on fertility. Our findings confirmed the assumption that current marijuana users are less likely to perceive a negative impact on fertility than past years or non-users, and thus one can conclude it is this perception that leads to such a high incidence of use among people who are actively trying to conceive, despite medically relevant concerns that cannabis use can negatively impact fertility.

It is also important to note that the 13% prevalence of past-year cannabis use likely represents an underestimation of the true prevalence of use among infertility patients, a fact highlighted by the data from Kaiser Permanente Health Care Institutions, USA (Young-Wolff et al. 2017). The higher prevalence found via toxicology versus that determined by self-reporting suggested that use has commonly been underestimated in survey studies. Likewise, in a study comparing umbilical cord sampling to a survey of self-reported cannabis usage in pregnancy in a US state with marijuana legalization, 22.4% of umbilical cord assays had detectable cannabis metabolites compared with only 6% of participants reporting use within the past 30 days (Metz et al. 2019). Of note, in the Metz et al. (2019) study the self-reported prevalence of cannabis use within the last year was 14.7% among these pregnant patients, which is similar to the 13% reported in our study. Given that marijuana was not yet legal for recreational use at the time of our survey, it is possible that participants were being even less forthcoming about cannabis use than in other reported studies, in which case the true prevalence in our patient population may be much higher. Patients may also not have been forthcoming about cannabis use if they believed that recreational drug use might exclude them from fertility care, which may be the case at other fertility clinics around the world, but is not at our fertility centre. Furthermore, the data from Statistics Canada demonstrates a growing rate of use in Canada from early 2018 until early 2019 suggesting that usage among infertility patients has likely continued to grow since legalization (Statistics Canada 2019).

While the process of recreational cannabis legalization plays out within Canadian borders, it is difficult to predict exactly how and if usage trends will be affected. In American states where MM is legal, higher rates of marijuana use are reported compared with non-legal states, which is hypothesized to be related to four societal mechanisms: existing state-level community attitudes and behavioural norms may lead to MM legalization; enacting MM laws may lead to reduced disapproval and perceived riskiness of use, medical endorsement for its use as a treatment and increased commercial availability, promotion and access (Cerda et al. 2012). While these proposed mechanisms were created in the context of MM legislation, they can be used to discuss recreational legalization and provide us with a framework to understand the current climate in Canadian society. Based on these mechanisms, it is reasonable to infer that many of them are already in place in much of our society and that the prevalence could remain relatively stable.

In our study, previous cannabis use at any time was predicted by having been born in Canada, by Caucasian ethnicity and by alcohol consumption. This differs to the previously mentioned study in the USA, which only demonstrated correlations between cannabis use and young age (22–25 years old) and Medicaid instead of private medical insurance (Metz et al. 2019). These differences between studies likely represent the difference between the general pregnancy population in the USA where private medical insurance plays a pivotal role in medical care compared with the population of patients included in this fertility clinic study who are generally older, are almost all covered under public health insurance and are of a more varied ethnic background.

Regardless of whether use increases, decreases or stays the same, the fact that 13% of patients seeking fertility consultation or treatment used cannabis within the past year should be alarming. Patients are typically only referred to a fertility clinic after at least 1 year of infertility; therefore, this should be a motivated group of patients looking to optimize their chances of successfully achieving a pregnancy, and one would expect a low level of cannabis use compared to the general population if cannabis is known to have a negative impact on fertility. The prevalence of use in our study is indicative of the mixed information on cannabis that is readily available to patients.

Our study highlights that those infertility patients who are current users of cannabis are less likely to perceive that there is a harmful effect of cannabis on fertility compared with those who have never used cannabis, suggesting that perceptions of harm are clear motivators of use while actively trying to conceive. In a study assessing online Tweet messages about cannabis use in pregnancy, of the 550 Tweets captured from 2006 to April 2017, 77.6% had a neutral tone, making it seem that the health effects of cannabis use in pregnancy and the post-partum period are unclear despite the known adverse outcomes in pregnancy (Dakkak et al., 2018). When performing a Google search of ‘marijuana and fertility’, reassuring headlines, such as the following, are common and likely contributing to public perception of little to no risk of use while trying to conceive: ‘Marijuana use does not lower chances of getting pregnant’ (Abdalla, 2018). These types of headline commonly cite two large survey studies in the USA both of which demonstrated no statistically significant difference in time-to-pregnancy and fecundability in non-users compared with daily users (Kasman et al., 2018, Wise et al., 2018). However, these studies were surveying the general population and thus cannot be assumed to be generalizable to people struggling with infertility. Recently, the Canadian Medical Association Journal published a short article about marijuana and fertility, highlighting some of the potential negative effects of marijuana use while actively trying to conceive. The article has the potential to influence the sentiment of articles reported online (Ilnitsky and Uum, 2019).

A critical issue that this study leads us to consider is whether the prevalence reported in our study merely indicates that infertility patients use cannabis at similar rates to those in Canadian society not dealing with fertility challenges or whether cannabis use is a contributing cause to the patient’s infertility and resulting need for fertility healthcare. We note that 16% (43/270) of the sample population was either using cannabis or gave up using cannabis due to infertility; however, 16% is not materially greater than the average usage rate in the broader Canadian population, so this indicates that marijuana may not be a key driver of infertility. A public perception of the safety and potential health benefits of cannabis is predominant in Canadian society but there are potentially harmful effects on both fertility and, most importantly, pregnancy. The effect of cannabis on male fertility, in particular on semen analysis parameters, has been studied and that information has been used to counsel patients on cessation (Pacey et al. 2014, du Plessis et al. 2015, Gunderson et al. 2015). Our study reflected that there is some public awareness of this effect since 40% of <1 year users perceived there to be a negative effect on male fertility compared with only 20% for female fertility. This discrepancy highlights that the contemporary understanding of cannabis’ effect on female fertility is less robust, but it does continue to garner attention. Despite our findings on marijuana use in our population compared to that in broader society, future research should focus on delineating the effects of cannabis use on female fertility and whether simple interventions to reduce use among patients with infertility can improve conception rates.

Furthermore, there is growing evidence of the potential detrimental effect of cannabis use in pregnancy, including an increased risk of preterm birth, neonatal morbidity and stillbirth (Varner et al., 2014, Metz et al. 2017, Corsi et al., 2019). Patients who are attending a fertility clinic are actively trying to conceive and therefore should be aware of these potentially detrimental effects in pregnancy as it is likely the most motivating factor for reducing use. In a cross-sectional survey study at a tertiary antenatal care clinic in Baltimore, MD, USA, researchers found that for women who successfully quit cannabis use in pregnancy, the most common motivator was to prevent harm to their pregnancy (Mark et al. 2017). We found in our study that 25% of past-year cannabis users quit as a result of infertility issues within that same year. However, only 9.4% of respondents reported that they were instructed to curb use by their doctor. This could be because doctors were not asking about cannabis use or were aware of the use and not recommending cessation. In either case, the fertility clinic may represent a practical, effective and under-utilized arena for intervention and cessation.

While there may be fertility centres around the world that require patients not to be using cannabis prior to fertility treatment, this is not typical in Canada where there are few eligibility criteria for fertility treatment, even for government-funded IVF cycles. Fertility clinics and government-funded fertility services that typically have eligibility criteria that encourage improvement in health status prior to treatment, such as a healthy weight and being a non-smoker, should consider whether being a non-user of cannabis should be added to the list of requirements to potentially improve pregnancy outcomes. As more jurisdictions globally consider legalization of marijuana, and with growing numbers of articles on the benefits and safety of marijuana posted on social media, it is anticipated that fertility clinics around the world will be seeing more patients using cannabis. Our study highlights the need to start addressing this issue with patients early on in their fertility treatment.

Studies to better characterize the complex relationship between cannabis, female fertility and patient care are warranted given the limited status of our scientific understanding and the perceived uncertainty of its effect among fertility patients. HCPs should be equipped with the evidence needed to accurately counsel patients who are using cannabis and receiving reproductive care. We hope this study of cannabis prevalence and perceptions among infertility patients helps to better prepare HCPs for addressing this issue with patients who are planning conception.