Approximately half of the total sample in this trial had a history of MDD, and a third had clinically significant baseline BDI-II scores (≥ 2 0; signifying moderate depression). When evaluating the relationship between these measures of depression and smoking outcomes, an association was found in which higher symptoms of depression were associated with greater smoking severity as well as poorer smoking cessation outcomes. More specifically, participants with a history of MDD reported an earlier age of cigarette smoking and greater nicotine dependence as evidenced by higher baseline Fagerström scores. Also, individuals with a history of MDD had higher nicotine withdrawal scores, greater craving scores and higher CO levels during smoking cessation treatment. Those with elevated baseline BDI-II scores smoked more cigarettes per day. In regard to smoking cessation outcomes, higher BDI-II scores were associated with a lesser likelihood of smoking abstinence, higher expired CO scores during treatment, higher nicotine withdrawal scores, and higher nicotine craving scores. These findings are similar to those in samples of smokers who do not have a substance use disorder.
Because there was no diagnosis of MDD, this study used a previous treatment history of MDD reported by the participants as a proxy for history of MDD. While this may be an underestimate of the history of MDD in our study sample, the rates we observed was similar to that seen in other studies.20
Among cigarette smokers, Hall and colleagues14
found 31% of a sample of 149 smoking treatment participants had a history of MDD. Others have reported similar rates.21,22
In this regard it has been suggested that individuals with low tolerance to mood disturbance have a greater propensity for drop out from substance abuse treatment23
and for early relapse to smoking after a quit attempt.24
The findings in the present study are consistent with this, as higher baseline depression scores were associated with lower smoking abstinence rates.
Overall, this report shows an association between depressive measures and smoking outcomes in which higher symptoms of depression are associated with poorer smoking cessation outcomes. Data from previous studies of the general population have been mixed in this regard. Anda and colleagues25
reported a lower rate of smoking cessation during a 9-year follow-up in smokers who scored higher on depressive symptoms at baseline compared with those who scored lower. Salive and Blazer26
reported on the 3-year incidence of quitting among smokers 65 years and older and found women with high baseline depression scores to have a 2-fold increase in quitting smoking (55%) compared to women with normal baseline depression scores (25%). Still other investigators5
have found no influence of depression on smoking cessation outcomes.
Haas and colleagues22
found that individuals with a history of MDD responded better to smoking cessation treatment that included a strong dose of CBT. Moreover, Hall and colleagues14
found that individuals with current depression responded better to smoking cessation treatment with motivational enhancement counseling sessions versus brief advice to quit. The current study also included a strong dose of CBT, and counseling attendance was a significant predictor of abstinence.11
Nevertheless, subjects with higher depression scores showed poorer smoking abstinence outcomes. Perhaps depression co-morbid with, drug or alcohol dependence is simply too strong to overcome.
As stated above, history of MDD or high BDI-ll scores were associated with more smoking (yrs, cig/day) and higher Fagerstrom nicotine dependence scores at baseline in the current study. Breslau and colleagues5
observed depression at baseline increased significantly the risk for daily smoking (OR 3.0) but did not decrease significantly smokers’ rate of quitting (OR 0.8). History of daily smoking at baseline increased significantly the risk for major depression (OR 1.9). Interestingly, this estimate was reduced when early conduct problems and prior alcohol use were controlled. It is unclear what the effect of other substances of abuse might have on this association. Indeed, substance abuse quantity and severity of dependence has been reported to be greater in smokers versus non-smokers,27,28,29
and more smoking is reported in comparisons of substance abusing versus non-abusing patients.30,31
This study also found an association between baseline BDI-II scores and nicotine withdrawal symptoms. The symptom overlap between nicotine withdrawal and depressive symptoms, including insomnia, anxiety, difficulty concentrating, somatic complaints, and changes in appetite may play a part in the strength of this association.
As stated above, depressed mood has often been associated with worse substance abuse treatment outcomes.9,10
Interestingly the current study did not find a significant relationship between mood and substance use during study treatment. This may have been due that fact that this was a secondary analysis and the study was not powered to answer that specific research question. Also, the participants in this trial were enrolled in substance abuse treatment for at least a month prior to study enrollment, which may have allowed for a more stable substance abuse outcome.
This study found substance abusers with either a history of MDD or an elevated BDI-II at baseline to have an earlier onset of cigarette smoking as well as worse smoking cessation outcomes. It remains unclear, however, what effect specific treatment of depressive symptoms might have on smoking cessation outcomes in this sample. In the current study, there was no difference in BDI scores during, and at the end of treatment, between SC treatment and control groups. Hall and colleagues32
conducted a 2 (nortriptyline versus placebo) ×2 (cognitive-behavioral therapy versus a health education control) × 2 (history of MDD versus no MDD history) randomized trial in 199 treatment-seeking smokers. They found that nortriptyline improved dysphoric symptoms that occurred after smoking cessation and that it improved abstinence rates greater than placebo, independent of MDD history. Brown and colleagues33
reported similar findings with bupropion and cognitive behavioral therapy. It is unclear if either of these antidepressant pharmacotherapies would have a differential effect in depressed substance abusers interested in quitting smoking.