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

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.