The effect size is similar to that of antidepressant treatment.

Many smokers cite relief of psychological symptoms as a reason for 
continued smoking. However, the relation between smoking and mental 
health is unclear. In this meta-analysis of 26 prospective, 
observational studies conducted in various countries worldwide, 
investigators compared changes in mental health (anxiety, depression, 
mixed anxiety and depression, quality of life, positive affect, and 
stress) at ≥6 weeks’ post–smoking cessation with changes after the 
same amount of time among people who continued to smoke.

After a median follow-up of 6 to 12 months, smoking cessation, 
compared with continued smoking, was associated with significant 
decreases in anxiety, depression, mixed anxiety and depression, and 
stress and significant increases in psychological quality of life and 
positive affect (all measured via questionnaires). The effect size was 
similar between participants from general populations and those with 
physical or psychiatric illnesses.

COMMENT

In this study, smoking cessation was associated with improved mental 
health outcomes. Although these observational associations do not 
prove causality, they do challenge widely held beliefs that smoking 
relieves psychological symptoms and that trying to quit smoking 
aggravates such symptoms. As the authors note, if the associations are 
causal, the effect size of smoking cessation is similar to that of 
drug treatment for depression or generalized anxiety disorder. At 
least, these results should inspire us to be more proactive in 
encouraging smoking cessation among patients with anxiety and 
depression.

Taylor G et al. Change in mental health after smoking cessation: 
Systematic review and meta-analysis. BMJ 2014 Feb 13; 348:g1151. (http://dx.doi.org/10.1136/bmj.g1151
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