Vaping transitions and incident depressive symptoms among young adults: a marginal structural model analysis.

The extent to which vaping influences depression is unclear but could be estimated through application of novel epidemiologic methods. Among a prospective cohort of young adults from California who screened negative for depression, we estimated repeated-measures marginal structural models to examine the association of 4 vaping transitions from time T to T + 1 (persistent use, discontinuation, initiation, persistent nonuse) with risk of clinically significant depressive symptoms at T + 1, simultaneously across three ~ 1.5-year time intervals between 2017 and 2021. Stabilized inverse probability of treatment and censoring weights adjusted for time-dependent confounders and selection bias. Among n = 3496 observations (1806 participants, mean pooled baseline age = 19.5), 8.1% reported persistent vaping from T to T + 1, 6.2% reported discontinuation (ie, use at T and no use at T + 1), 6.5% initiated e-cigarettes (ie, no use at T and use at T + 1), and 79.2% reported persistent nonuse at both time points. Compared to persistent vaping at 2 waves, persistent nonuse (relative risk [RR] = 0.76; 95% CI, 0.62-0.93) and discontinuation (RR = 0.71; 95% CI, 0.52-0.96) were associated with lower risk of depression. Associations were robust to sensitivity analyses, including restricting to tobacco-naive participants and varying temporal assumptions to reduce potential for reverse causation. Young adults who consistently avoid or discontinue vaping may be protected from depressive symptom occurrence.