Substance Use among Exclusive Electronic Cigarette Users and Dual Combustible Cigarette Users: Extending Work to Adult Users.

BACKGROUND Electronic cigarettes (e-cigarettes) have become increasingly popular in recent years. Existing evidence indicates e-cigarettes used in isolation are less harmful than combustible cigarettes, yet emerging work has demonstrated that adults use e-cigarettes largely in combination with combustible cigarettes (i.e. dual use). Despite this data, little is understood about how exclusive and dual e-cigarette users may differ across behavioral outcomes, such as substance use dependence and behaviors among adults. OBJECTIVES Thus, the current project examined differences in e-cigarette dependence, problematic alcohol use, cannabis use, and nonmedical prescription opioid use (e.g. methadone and oxycodone) across both exclusive and dual e-cigarette adult users. RESULTS Participants included 531 (53.6% female; Mage = 35.29 years, SD = 10.44) adults with past-month e-cigarette use. Dual users reported greater e-cigarette dependence, alcohol use, current cannabis use, and endorsement of nonprescription opioid use. Conclusions/Importance: Importantly, this work suggests that adults who use both combustible and e-cigarettes may constitute a group more vulnerable to experiencing problematic substance use and more severe e-cigarette dependence than exclusive e-cigarette users.