Elsevier

The Lancet

Volume 357, Issue 9272, 16 June 2001, Pages 1929-1932
The Lancet

Articles
Smoking cessation and the course of major depression: a follow-up study

https://doi.org/10.1016/S0140-6736(00)05064-9Get rights and content

Summary

Background

Smokers with a history of major depression who attempt to stop smoking have a higher risk of failure than non-depressed smokers. Anecdotal and post-hoc data suggest that those who successfully abstain are at increased risk of depression compared with individuals who continue to smoke. However, these studies confound effects of abstinence and history of depression. We aimed to assess whether there is an increased risk of depression and for how long that increase lasts.

Methods

We enrolled 100 smokers (>pack per day) with a history of major depression, but who were currently free from major depression and had not been on antidepressant medicine for at least 6 months, in a 2-month smoking-cessation trial. The primary outcome was recurrence of major depression, which we assessed by structured clinical interviews 3 and 6 months after the end of treatment. We verified smoking status by serum-sample cotinine concentrations.

Findings

76 participants (42 successful abstainers, 34 smokers) were followed up. 13 abstainers and two smokers had an episode of major depression (odds ratio 7·17 [95% CI 1·5–34·5]; Kaplan-Meier survival curve, log-rank statistic 9·11 [p = 003]). Risk of major depression was similar between the first and second 3 months of follow-up.

Interpretations

Smokers with a history of depression who abstain from smoking are at significantly increased risk of developing a new episode of major depression. This risk remains high for at least 6 months.

Introduction

In 1988, we noted that smokers attending a smoking-cessation clinic had a much higher than average frequency of past episodes of major depression,1 and even those who had been free of such episodes for many years were twice as likely as those who had never been depressed to start smoking again. In many clinical and epidemiological investigations, associations have been shown between smoking and major depression, and depression and inability to stop smoking;2, 3, 4, 5, 6, 7 although in other studies this association has not been shown.8, 9 A likely explanation seemed to be that smokers' depressive symptoms returned when they tried to stop smoking. However, in the early 1990s, depression was not thought to be a symptom of smoking withdrawal. Therefore, we assessed smokers, with and without a history of major depression, and noted that depressive symptoms were significantly more frequent and intense during nicotine withdrawal in smokers with a history of major depression than in those without such a history.10

Some smokers also had episodes of major depression. Unlike withdrawal symptoms, these episodes did not subside within 1 or 2 weeks of stopping smoking and sometimes did not start for several weeks after cessation.7, 11, 12 However, many of these findings were merely anecdotal and did not control for the incidence of depression among individuals with a history of depression who continued to smoke. Any individual with a history of major depression is more likely to develop depression than people without that history, irrespective of whether they have stopped smoking.13 A study of the efficacy of an antidepressant drug to help smokers with a history of major depression to stop smoking gave us an opportunity to prospectively investigate this issue.

In cessation studies, abstinent participants are normally followed up for at least 6 months to check whether differences between drug and placebo groups disappear after treatment is withdrawn. We followed up all participants for 6 months after active treatment ended, and recorded smoking status and onset of new psychiatric symptoms or diagnoses. All people in the study had a history of major depression; hence we were able to prospectively assess the effect of smoking cessation on the risk of relapse to major depression, while controlling for participants' history of depression.

Section snippets

Participants

Smokers were mostly recruited by newspaper advertisements. We screened respondents by telephone for history of smoking, depression, and use of antidepressant drugs. Smokers who had no history of depression were referred to other programmes, as were smokers who had a history of major depression and who had taken antidepressant drugs in the past 6 months. If phone contact suggested that the candidates were suitable a personal interview was arranged. Interviews included the sections of the

Treatment

Eligible smokers were randomly assigned sertraline or an identical placebo. They were told that the study drug was an antidepressant that would take several weeks to work, and were advised to select a day to stop smoking as close to 21 days after starting treatment as possible. 9 weeks after the start of the study, participants reported their smoking status, which was confirmed by serum cotinine concentration. Sertraline or placebo was gradually reduced and stopped in the next 2 weeks. We

Results

100 smokers came to their quit appointment on their chosen date to stop smoking (3 weeks after start of treatment). Follow-up data were obtained for 76 participants. They smoked a mean of 27·4 (SD 9·2) cigarettes daily. Mean age was 43·7 years (11·3). 49 (64%) were women and 65 (86%) were white. 43 (57%) had had recurrent episodes of major depression and 58 (76%) had sought professional help. Mean time since their last depressive episode was 7–4 (7·3) years. The table shows baseline

Discussion

Smokers with a history of major depression who stopped smoking were seven times more likely to have a recurrence of major depression than people who continued to smoke. Our study was prospective and we controlled for a history of depression. However, it was a follow-up study not a randomised trial.

A randomised controlled trial of the relation between smoking cessation and depression is neither ethical nor practical. Smokers cannot be randomly selected to abstain from or to continue smoking, or

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