Longitudinal Association Between Smoking Abstinence and Depression Severity in Those With Baseline Current, Past, and No History of Major Depressive Episode in an International Online Tobacco Cessation Study.

Introduction: We use multilevel modeling to parse out the effects of time-varying smoking abstinence and baseline depression (history and severity) on depression severity over 1 year.
Aims and Methods: Participants were 1000 smokers recruited worldwide for an online randomized controlled tobacco cessation trial. We examined whether changes in depression severity over time were associated with self-reported 7-day point prevalence smoking status assessed at 1-, 3-, 6-, and 12-month follow-up (FU) using baseline major depressive episode (MDE) history and baseline depression severity as time-invariant covariates. We present depression severity means and smoking abstinence at each FU.
Results: Regardless of concurrent abstinence status, baseline MDE history was significantly related to depression severity over time: those reporting a past MDE had worse depressive symptoms over time compared with those reporting no MDE history. Baseline depression severity interacted significantly with time-varying abstinence status: for every 1-unit increase in baseline scores on the Center for Epidemiological Studies-Depression Scale (CES-D), individuals who were smoking at FU reported CES-D scores that were 0.17 points higher than those who were abstinent. In this context, nicotine dependence, gender, age, or marital status did not affect depression severity.
Conclusions: In the context of cessation, having an MDE history plays a significant role in the trajectory of depression severity over the course of 1 year, regardless of abstinence status. Abstinence is related to lower depressive symptoms at each FU, and this effect was stronger at higher levels of baseline depression severity.
Implications: This study indicates that depressive symptoms are not exacerbated among individuals who are quitting smoking at 1-, 3-, 6-, and 12-month FUs. Depression severity is worse with a baseline history of MDE. Further, those with high baseline depression severity who continue smoking have worse depressive symptoms throughout a 1-year period compared with their abstinent counterparts.
(Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco 2020.)