IMPORTANCE The prevalence of the use of electronic cigarettes (e-cigarettes) in the United States has grown rapidly since their introduction to the market more than a decade ago. While several studies have demonstrated an association between combustible cigarette smoking and depression, the association between e-cigarette use and depression has not been thoroughly studied. OBJECTIVE To examine the association between e-cigarette use and depression in a nationallyrepresentative sample of the adult population in the United States. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional study of the Behavioral Risk FactorSurveillance System database, 2016 to 2017. The Behavioral Risk Factor Surveillance System is the largest national telephone-based survey of randomly sampled adults in the United States. A total of 892 394 participants with information on e-cigarette use and depression were included. Data analysis was conducted in May 2019.EXPOSURES Electronic cigarette use status defined by self-report as never, former, or current use. MAIN OUTCOMES AND MEASURES Self-reported history of a clinical diagnosis of depression. RESULTSOf the 892 394 participants (414 326 [29.0%] aged Ն60 years; 502 448 [51.3%] women), there were 28 736 (4.4%) current e-cigarette users, of whom 13 071 (62.1%) were aged between 18 and 39 years. Compared with never e-cigarette users, current e-cigarette users were more likely to be single, male, younger than 40 years, and current combustible cigarette smokers (single, 120 797 [24.3%] vs 10 517 [48.4%]; men, 318 970 [46.6%] vs 14 962 [60.1%]; aged 18-39 years, 129 085 [32.2%] vs 13 071 [62.1%]; current combustible cigarette use, 217 895 [7.9%] vs 8823 [51.8%]). In multivariable adjusted models, former e-cigarette users had 1.60-fold (95% CI, 1.54-1.67) higher odds of reporting a history of clinical diagnosis of depression than never users, whereas current e-cigarette users had 2.10 (95% CI, 1.98-2.23) times higher odds. Additionally, higher odds of reporting depression were observed with increased frequency of use among current e-cigarette users compared with never users (daily use: odds ratio, 2.39; 95% CI, 2.19-2.61; occasional use: odds ratio, 1.96; 95% CI, 1.82-2.10). Similar results were seen in subgroup analyses by sex, race/ethnicity, smoking status, and student status. CONCLUSIONS AND RELEVANCEThis study found a significant cross-sectional association between e-cigarette use and depression, which highlights the need for prospective studies analyzing the longitudinal risk of depression with e-cigarette use. If confirmed by other study designs, the potential mental health consequences may have regulatory implications for novel tobacco products.

e-Cigarettes are generally perceived to be less harmful than traditional cigarettes. 1 A considerable public health challenge is their use among young adults who have never smoked and among vulnerable subgroups, including individuals with mental health conditions and pregnant women. [2][3][4] The rapidly evolving e-cigarette market, outdated tobacco laws and regulations, and the recent outbreak of e-cigarette or vaping product use-associated lung injuries highlight the need for up-todate data on e-cigarette use.

IMPORTANCEUpdated data on the patterns of e-cigarette use among adults in the US are needed. OBJECTIVE To examine recent patterns in current and daily e-cigarette use among US adults. DESIGN, SETTING, AND PARTICIPANTS This repeated cross-sectional study used data from the 2017, 2018, and 2020 Behavioral Risk Factor Surveillance System, a nationally representative statebased survey of noninstitutionalized US adults. A total of 994 307 adults 18 years and older who were living in states and territories that provided data on e-cigarette use in 2017 (53 states and territories), 2018 (36 states and Guam), and 2020 (42 states and Guam) were included. MAIN OUTCOMES AND MEASURESThe weighted prevalence of current (past 30 days) and daily e-cigarette use was estimated for each year, and changes in prevalence from 2017 to 2020 were assessed, first overall and then stratified by participant characteristics, including state or territory of residence. RESULTS Among 994 307 adults from states with data on e-cigarette use, 429 370 individuals (weighted 51.3% female) were participants in the 2017 survey, 280 184 (weighted 52.1% female) were participants in the 2018 survey, and 284 753 (weighted 52.1% female) were participants in the 2020 survey. The weighted proportions of young adults aged 18 to 24 years were 12.6% in 2017,

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