"I'm both smoking and vaping": a longitudinal qualitative study of US young adults who tried to quit smoking cigarettes by using electronic cigarettes.

Objective: To describe how young adults use electronic cigarettes (electronic nicotine delivery systems (ENDS)) for smoking cessation and reasons why they may or may not successfully quit smoking.

Methods: Longitudinal qualitative data were collected annually from 2017 to 2019 for 25 young adult tobacco users (aged 18-29 years) in California (USA) who used ENDS to quit/reduce smoking. Thematic and trajectory analyses were used to identify key within-person and between-person changes in tobacco/nicotine use over time.

Results: Five types of tobacco use transition were identified among baseline dual users of cigarettes and ENDS: (n=8), (n=6), (n=5), (n=4) and (n=2). Participants' ENDS use behaviour varied over time in terms of vaping quantity and device characteristics (eg, changing nicotine concentrations/flavours, switching between multiple devices). Three themes that related to successfully replacing cigarettes with ENDS were and . Four themes for unsuccessful replacement were , and .

Conclusions: Young adults' experiences with using ENDS as a smoking cessation aid were highly variable. Adequate nicotine delivery and perceived safety and benefits contributed to successfully reducing or quitting cigarettes. Providing behavioural counselling and standardising ENDS products may enhance cessation for young adults.