The use of both cannabis and nicotine/tobacco products within the same individual (broadly defined as co-use) is prevalent in the United States (US) and globally (Agrawal et al., 2012, Agrawal and Lynskey, 2009, Goodwin et al., 2018, Hindocha et al., 2016a, Leatherdale et al., 2006, Leatherdale et al., 2007, Richter et al., 2004, Schauer et al., 2016, Schauer et al., 2016, Schauer et al., 2017, Tullis et al., 2003) and is associated with greater prevalence of psychiatric and psychosocial problems, additive toxicant exposure, and implications for treatment and related health outcomes (Lemyre et al., 2018, McClure et al., 2020, Meier and Hatsukami, 2016, Peters et al., 2014, Ramo et al., 2012, Smith et al., 2020). Primary care medical settings represent an important location in which to screen, advise, refer and potentially intervene on problematic substance use (Sayre et al., 2020).

Tobacco clinical practice guidelines in the US highlight the importance of addressing tobacco use in the primary care setting through screening and brief interventions (Fiore et al., 2008). Tobacco use screening has been widely implemented and is well established in primary care, but cessation assistance and connection to treatment is not as common (Jamal et al., 2015). Further, implementing screening questions for other forms of nicotine use (nicotine vaping, electronic cigarettes, etc.) and the co-use of cannabis has been not as well integrated, despite common co-occurrence. While primary care presents an opportunity to screen and intervene on tobacco/nicotine and cannabis co-use, little work has been done in this area. Two studies have found that cannabis co-use among primary care patients who also used tobacco was common (20–30 % of those currently smoking cigarettes) (Lapham et al., 2017, Thrul et al., 2020), while another found nearly 1 in 5 who report cannabis use also use tobacco (Lapham et al., 2018), providing support for routine co-use screening, referral and/or intervention in a primary care context. Few treatment-focused studies have been conducted on cannabis-tobacco co-use among a primary care population. Two observational studies have shown that: 1) primary care patients who co-use cannabis and tobacco had poorer tobacco cessation outcomes (compared to patients only using tobacco), but only among those who were using cannabis non-medically and not among those co-using cannabis for medical purposes (Voci et al., 2020), and 2) cannabis co-use was not associated with engagement in a tobacco quit-line or tobacco cessation (McClure and Lapham, 2021).

Within the context of a cross-sectional cannabis survey among primary care patients in Washington state (Lapham et al., 2022), which has a mature legal cannabis marketplace (non-medical use of cannabis has been legal since 2012), we sought to examine differences in cannabis use outcomes comparing patients who reported co-use of tobacco and/or nicotine products to those who only reported current cannabis use. Co-use is defined broadly in the current analysis as the use of both cannabis and tobacco/nicotine endorsement within a given patient. While several studies have demonstrated more severe cannabis dependence, greater cannabis use rates, and more severe clinical presentations among those who co-use cannabis and tobacco (Dierker et al., 2018, Hindocha et al., 2021, Hindocha et al., 2015, McClure et al., 2018), this has not been demonstrated in a primary care sample. Further, few studies to date have differentiated between modes of nicotine delivery and how that may affect cannabis co-use associations. The cannabis and nicotine product landscapes have evolved rapidly in the US, which may contribute to numerous combinations of co-use and may affect the relationship between substances. Therefore, the purpose of this secondary analysis was to examine measures of cannabis exposure and use characteristics, health symptoms managed, and problematic cannabis use among surveyed adult primary care patients who co-use cannabis and nicotine compared to patients who endorse current cannabis use only. The aims of this analysis were to: 1) evaluate differences on cannabis use outcomes between cannabis-only patients compared to those with any nicotine co-use, and 2) evaluate differences in cannabis use outcomes, stratifying by specific type of nicotine co-use (e.g., cigarettes, vaping nicotine, or both).