Co-Use of Nicotine Products and Cannabis and Its Association with ENDS Dependence Among U.S. adults Frequently Using ENDS.

Background: People who use electronic nicotine delivery systems (ENDS) often also use other nicotine products and cannabis. This study explores the co-use of these substances among adults frequently using ENDS and examines its association with ENDS dependence. Objectives: Data came from wave 5 (February-April 2023) of a longitudinal study. A subsample of 1,290 U.S. adults (21+) who self-reported using ENDS 5+ days/week and uploaded photos of their most used ENDS devices and liquids, reported their use of nicotine products and cannabis in the past 30 days, days per week they used these substances, and ENDS dependence. Co-use patterns were categorized as: (1) exclusive ENDS use, (2) ENDS-other nicotine product(s) co-use, (3) ENDS-cannabis co-use, (4) ENDS-other nicotine product(s)-cannabis co-use. We examined the association between co-use and dependence, measuring co-use as the use of nicotine products and cannabis in the past 30 days and on 5+ days/week. ANCOVAs and multiple linear regression analyses were conducted. Results: After controlling for sociodemographic and device and liquid characteristics, participants co-using ENDS-cannabis (n = 344, 26.6%) reported significantly higher ENDS dependence (e-cigarette dependence scale [EDS, range 0-4, 4 being most dependent] = 2.5) compared to those co-using ENDS-other nicotine product(s)-cannabis (n = 81, 6.2%, EDS = 2.3, p < 0.05), and co-using ENDS-other nicotine product(s) (n = 127, 9.8%, EDS = 2.2, p < 0.05). Conclusions: Co-use of ENDS-cannabis is common among adults frequently using ENDS and is associated with greater ENDS dependence compared to other co-use patterns. Further research is needed to explore impacts of frequent co-use beyond dependence and to inform prevention efforts.