Electronic cigarette use is associated with depressive symptoms among smokers and former smokers: Cross-sectional and longitudinal findings from the Constances cohort.

Aims: To examine the cross-sectional and longitudinal associations between depressive symptoms and electronic cigarette (e-cig) use in a large population-based sample while taking into account smoking status and sociodemographic confounders.

Methods: Participants from the French Constances cohort were included from February 2012 to December 2016. Smoking status, e-cig use (never/ever/current) and nicotine concentration were self-reported. Depressive symptoms were measured with the Center for Epidemiologic Studies Depression (CES-D) scale. Logistic regressions were used to provide odds ratios (ORs) and 95% confidence intervals (95%CI) of e-cig use according to depressive symptoms, adjusting for age, sex and education.

Results: In cross-sectional analyses (n = 35,337), depressive symptoms (i.e. a CES-D score ≥ 19) were associated with both ever (OR [95%CI]: 1.67 [1.53-1.82]) and current (1.73 [1.53-1.96]) e-cig use with a dose-dependent relationship (p-trend<0.001). In longitudinal analyses (n = 30,818), depressive symptoms at baseline were associated with current e-cig use at follow-up (2.02 [1.72-2.37]) with a similar dose-dependent relationship. These associations were mainly significant among smokers or former smokers at baseline. Furthermore, among smokers at baseline, depressive symptoms were associated with dual consumption at follow-up (1.58 [1.41-1.77]), whereas among former smokers, they were associated with either smoking only (1.52 [1.34-1.73]) or e-cig use only (2.02 [1.64-2.49]), but not with dual consumption (1.11 [0.73-1.68]) at follow-up. Finally, depressive symptoms were positively associated with nicotine concentration among e-cig users at baseline.

Conclusions: Depressive symptoms were positively associated with e-cig use in both cross-sectional and longitudinal analyses with a dose-dependent relationship. In addition, nicotine concentration and depressive symptoms were positively associated.