Co-occurring Use of Cannabis and Tobacco and the Presence of Acute Respiratory Symptoms among Young Adult Light and Intermittent Smokers.

BACKGROUND: Cannabis use and intermittent smoking are becoming increasingly prevalent among young adults. Thus, identifying health consequences of co-occurring use of these substances represents an emerging research priority. Purpose/
Objectives: This study evaluated the relationship between tobacco/cannabis co-use and acute symptoms of respiratory illness among young adult intermittent smokers. We hypothesized that tobacco/cannabis co-use would be more strongly associated with respiratory symptoms relative to use of neither or one product.
Methods: A secondary analysis of a three-year observational study was conducted. Non-daily smokers (n = 563) aged 18-24 were recruited via social media and completed electronic surveys at baseline and annually for two years, producing three total assessments. Past-two-week use of tobacco and cannabis was measured at each assessment, as was severity of six acute respiratory symptoms. The respiratory measure was dichotomized to indicate the presence or absence of symptoms.
Results: Tobacco/cannabis co-use decreased from 54.8% at baseline to 43.4% at year two (p < .001). Mean respiratory symptoms also declined significantly over time (ps < .05). At each timepoint, co-use was more strongly associated with presence of respiratory symptoms than the use of neither product (aORs = 2.73-4.39, ps ≤ .013). Co-users were also 38%-183% more likely to endorse the presence of respiratory symptoms than single product users at each timepoint (aORs = 1.38-2.83, ps = .023-.212). Conclusions/Importance: Although co-occurring use of tobacco and cannabis by young adults may represent experimental use of multiple substances, it may also promote or exacerbate acute symptoms of respiratory illness. Further exploration with more granular patterns of co-use and across different routes of administration is warranted.