Anecdotal evidence and several studies have linked depression to smoking and suggested that depression contributes to the inability to quit smoking. Glassman and colleagues studied patients during smoking cessation to determine if they were at increased risk of clinical depression.
Newspaper advertisements were used to recruit 100 smokers who wanted to quit and had a history of major depression. At intake, participants were screened to exclude those with current depressive illness and those who had taken antidepressant drugs within the previous six months. Eligible smokers were randomly assigned to receive sertraline or placebo. Smoking status was assessed after nine weeks, and treatment was gradually discontinued over the following two weeks. Patient status was assessed three and six months after stopping treatment.
The mean age of the participants was 43.7 years, and each person smoked an average of 27 cigarettes per day. Most (86 percent) were white, and 64 percent were women. The average time since the last major depressive episode was seven years. Follow-up data were obtained on 76 participants, including 44 who successfully quit smoking. Among those who quit, 13 (31 percent) developed symptoms of major depression compared with two (6 percent) who continued to smoke. New episodes of depression were as common in the second three months after quitting as they were around the time of withdrawal. In those who quit, depression was more common in persons taking placebo than in persons taking sertraline (43 percent compared with 19 percent).
The authors conclude that smoking cessation is a significant risk factor for recurrence of major depression for at least six months after quitting smoking.