Bidirectional Association Between E-Cigarette Use and Depression: A Meta-Analysis.

Introduction: Previous studies have indicated the potential bidirectional association between the use of e-cigarettes (ECs) and depression. However, this hypothesis is yet to be thoroughly investigated. In this meta-analysis, the two-way relationship is examined.

Methods: As of November 2024, major electronic databases were searched. Two sets of pooled risk estimates were computed by employing random effects models: one for EC use predicting depression and the other for depression predicting EC use. The forms of depressive presentation involved in this study include major depressive disorder, dysthymia, and general depressive symptoms. The results were presented in terms of adjusted odds ratios (ORs) along with 95% confidence intervals (CIs).

Results: We identified a total of 1601 references and included 27 studies involving 1 671 773 participants. Both current EC use (OR 1.96, 95% CI: 1.73-2.23) and ever EC use (OR 1.88, 95% CI: 1.59-2.21) could notably forecast depression. Pooled results also indicated that depression might significantly predict current EC use (OR 1.36, 95% CI: 1.15-1.61) and ever EC use (OR 1.53, 95% CI: 1.25-1.88).

Conclusion: EC use might be a significant predictor for depression and depression might be a significant predictor for EC use, highlighting the need to strengthen mental health warnings on e-cigarettes and integrate EC use screening in depression assessments.

Implications: Considering the bidirectional link between EC use and depression, clinical screening, public health interventions and stricter marketing regulation are crucial to mitigate risks. Future research should focus on the mechanisms and causal pathways of e-cigarettes and depression.