Depressed smokers are an understudied population. They are typically excluded from smoking cessation trials. Most studies designed specifically to examine the effectiveness of a given treatment for smoking cessation, exclude individuals with depression (Hurt et al 1997
; Jorenby et al 1999
; Jack et al 2003
). The paucity of clinical research in this area, despite the strong epidemiologic link between depression and smoking, is likely related to the premise that depressed smokers will not accept or tolerate smoking cessation interventions.
Are depressed smokers willing to stop smoking? Prochaska and colleagues (2004)
showed that in fact about a fourth of depressed smokers surveyed were eager to quit smoking, and were willing to take action to quit within 30 days. This study also found that depression severity and history of depression recurrence were not related to willingness to try to quit smoking among depressed outpatients. Haug and colleagues (2005)
showed that 53 of 154 depressed smokers were willing to embark on a smoking cessation treatment plan that included behavioral counseling, nicotine patch, and bupropion. Haug and colleagues also found that severity of depression symptoms and depression history were unrelated to acceptance of smoking cessation treatment. On the other hand, few chronic psychiatric inpatients are ready to try to quit smoking (Hall et al 1995
Are depressed smokers able to stop smoking? Data are mixed on the effects of depression severity or history of depression on quit rates. Anda and colleagues (1990)
showed in an epidemiologic, cross-sectional study, that smokers with higher depression scores at the start of smoking cessation treatment were less likely to have quit eight years later than smokers not depressed at baseline (10% vs 18% quit). However, John and colleagues (2004)
, in a cross-sectional analysis of 4,075 smokers with past (lifetime) or current (12-month) diagnosis of depression, showed no difference in smoking cessation three years later compared to those without a mood disorder. A recent meta-analysis by Hitsman and colleagues (2003)
, looked at 15 published studies and found no difference in either short-term (less than 3 months) or long-term (greater than 6 months) abstinence rates between smokers positive versus negative for history of depression. A study of the effect of baseline depressive symptoms on smoking outcomes in 600 African American smokers, found that baseline depression also did not correlate with cessation rates at study endpoint (Catley et al 2005
). The preponderance of the evidence implies that depression does not adversely affect smoking quit rates; ie, smokers with depressive disorders are able to quit smoking at the same rates as nondepressed smokers.
The progression of depressive symptoms over the course of smoking cessation treatment, appears to be a more consistent negative correlate of quitting smoking. Killen and colleagues (1996)
have shown that worsening of depression during smoking cessation treatment, even in subjects who do not meet criteria for major depression at start of treatment, predicts a worse outcome in quitting smoking. Others have also found that individuals who become depressed while trying to quit smoking, are less likely to be successful at quitting (Cinciripini et al 2003
; Levine et al 2003
; Catley et al 2005
). Burgess and colleagues (2002)
have demonstrated that a delayed increase in depressive symptoms during smoking cessation treatment, as oppose to an initial short-lived increase or a steady decrease, is associated with lower quit rates. This is an interesting finding, implying that dysphoria in the acute withdrawal period may be different from dysphoria that begins or progresses after acute withdrawal has abated.
In summary, smoking quit rates are not clearly associated with prior history of depression, depressive symptoms at the start of smoking cessation treatment, or even necessarily briefly depressed mood in the acute withdrawal period. However, the trajectory of mood symptoms over the course of smoking cessation treatment does appear to impact quit rates: namely, worsening of depression after quitting appears to be a risk-factor for poor smoking outcomes. So who is likely to get depressed while quitting? Common clinical wisdom holds that individuals with history of depression are particularly vulnerable to worsening mood symptoms during smoking cessation. What is the evidence to support the notion that depressed smokers are more vulnerable to depression while quitting than nondepressed smokers?
A study by Glassman and colleagues (2001)
examined 76 smokers with a past history of major depressive disorder, all euthymic and off of antidepressant medication at the start of smoking cessation treatment, in order to determine the rates of recurrent depression in abstainers versus nonabstainers. Subjects were enrolled in a 2-month smoking cessation trial, and recurrence of major depression was assessed by structured clinical interviews at three and six month intervals. Thirteen of 42 successful abstainers had a recurrence of major depression; whereas two of 34 smokers had a recurrence of major depression. The findings demonstrate that depressed smokers who quit smoking are more likely to relapse to depression than depressed smokers who keep smoking; but only a minority of depressed smokers will get depressed. The study did not include a comparison group of nondepressed smokers, and so does not address the question of whether depressed smokers are at higher risk for depression than nondepressed smokers during quitting.
Covey and colleagues (1997)
compared the rates of occurrence of major depression with smoking cessation, among smokers with no prior diagnosis of depression, smokers with one prior major depressive episode, and smokers with recurrent major depressive disorder (Covey et al 1997
). Smokers who succeeded in abstaining from cigarettes for a 10-week smoking cessation program, were followed up three months after quitting (N = 126), and assessed for a major depressive episode using DSM-III-R criteria. Two of 91 subjects with no history, four of 24 subjects with past single major depression, and three of 10 subjects with past recurrent major depression, developed a major depressive episode by 3-month follow-up. In the absence of a comparison between those who did and did not successfully quit smoking, the results of the study are difficult to interpret. Those who continued smoking might have relapsed to major depression at the 3-month follow-up at the same rates as those who quit, given the recurrent nature of depressive disorders, particular in the absence of treatment. Nonetheless, the study does provide some preliminary evidence that those with prior depressive disorders, who quit smoking, are more likely to have a major depressive episode in the months following smoking cessation, than those with no prior depression history.
Even more remarkable is the apparent resiliency of smokers with depressive disorders in the face of smoking cessation, a significant physical and psychological stressor. The covey study found that 24 of 34 smokers, more than two-thirds the sample with a prior diagnosis of major depression, did not have a recurrence of major depression after quitting smoking, even without antidepressant medication or other apparent intervention. Two of the subjects who did have a recurrence of depression, experienced depressive symptoms for only two days before restarting effective antidepressant therapy.
In a study by Covey et al, placebo was compared with bupropion for smoking cessation treatment (N = 429). Depressive symptoms were measured at weeks 8 and 12. Changes in depressive symptoms were measured at these endpoints, and did not differ for those with and without a past history of depression (Cox et al 2004
The clinical studies reviewed above have included depressed smokers who were euthymic (ie, not depressed) at the initiation of smoking cessation treatment, and not on antidepressant therapy. Presumably, these individuals had a less severe form of depression, since they were able to be well without treatment for depression for some period of time. To our knowledge, smokers who are depressed at baseline, on or off medication, and smokers with more severe forms of depression, have not been included in smoking cessation studies comparing clinical outcomes with nondepressed smokers.
Is there any evidence that stopping smoking actually improves depression? Burgess and colleagues (2002)
found that of 163 smokers with a past history of depression, 40% experienced an increase in depression symptoms during quitting, and 47% experienced a decrease in depression symptoms during quitting. In a national household survey on drug abuse (N = 13,827), although current smokers were found to be at highest odds for suffering from depression, followed by former smokers, followed by nonsmokers; odds of depression were lower with more elapsed time since last smoking (Martini et al 2002
). Thorsteinsson and colleagues (2001)
used nicotine replacement therapy in smokers who were depressed at the initiation of smoking cessation treatment, independent of past history of depression, and examined both smoking and mood outcomes. One patient in the placebo group (N = 20), and no patients in the nicotine group (N = 18), became more depressed; and there was a trend for improved mood symptoms in those subjects who remained abstinent from cigarettes for 29 days. This study was limited by small sample size. A study by Kahler and colleagues (2002)
looked prospectively at 179 smokers with a history of major depression, and found that continuous abstinence was associated with short- and long-term reductions in depressive symptoms (Kahler et al 2002
). Although limited, these data suggest that abstinence may contribute to mood gains.
Improved mood with sustained abstinence from cigarettes may be related to brain serotonin levels. A study by Malone and colleagues (2003)
showed an inverse relationship between amount of cigarettes smoked and serotonin function, as measured by fenfluramine challenge tests and cerebro-spinal fluid levels of 5-hydroxyindoleacetic acid. Another potential explanation for improved mood with smoking cessation is a decrease in hypercholinergic neurotransmission at the nicotinic acetylcholine receptors (nAChR) (Shytle et al 2002