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J Adolesc Health. 2019 Jun;64(6):770-775. doi: 10.1016/j.jadohealth.2019.02.019.

Adolescents' E-Cigarette Use: Increases in Frequency, Dependence, and Nicotine Exposure Over 12 Months.

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Department of Psychiatry and Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, California.
Stanford Prevention Research Center, Department of Medicine, Stanford University, Stanford, California.
University of California, Berkeley, Berkeley, California.
Division of Adolescent & Young Adult Medicine, University of California, San Francisco, San Francisco, California. Electronic address:



This study examined changes in e-cigarette and dual-use frequency, levels of nicotine exposure and e-cigarette dependence, and device and e-liquid preferences over 12 months.


Adolescents (N = 173, aged 13-18 years) who reported past-month e-cigarette use and at least 10 lifetime uses were recruited from the San Francisco Bay Area. The sample was 75.1% male, 54.9% non-Hispanic White, mean age 16.6 years (standard deviation = 1.2); 26.6% reported past-month cigarette smoking at baseline (i.e., dual use). At baseline, 6-month, and 12-month follow-up, participants provided saliva samples for cotinine testing and self-reported e-cigarette use frequency, dependence, past-month smoking, product preference, and flavor preference.


Most (80.3%) were still using e-cigarettes at 12 months, and daily use increased from 14.5% to 29.8%. Model testing indicated an overall increase from baseline to 12 months in frequency of e-cigarette use (F(2, 166) = 5.69, p = .004), dependence (F(2, 164) = 5.49, p = .005), and cotinine levels (F(2, 103) = 4.40, p = .038). Among those reporting only e-cigarette use at baseline, 28.8% reported combustible cigarette use during follow-up. Among those reporting dual use at baseline, 57.1% were still dual using at 12 months, 31.4% reported e-cigarette use only, and none abstained from both products. Higher nicotine delivering e-cigarette devices (i.e., Juul, mods) became more popular over time, whereas flavor preferences (i.e., fruit, mint/menthol, and candy) remained stable.


Adolescents' e-cigarette use persisted over a 12-month period with significant increases in frequency of use, nicotine exposure, and e-cigarette dependence. Transitions from single to dual and dual to single nicotine product use were observed in approximately one in three users over the study period.


Addiction; Adolescent; Cigarettes; Dependence; E-cigarette; ENDS; Nicotine

[Available on 2020-06-01]

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