Although it has long been established that tobacco smokers can lessen the harmful effects of smoking on their physical health by quitting, the effects of smoking cessation on mental health haven't been seen as so clear cut.

Smokers are sometimes wary of even attempting to kick the habit because they believe smoking lessens depression, anxiety, and stress, but the opposite may actually be true. A new review of the literature on this subject has found evidence that quitting has significant mental health benefits.

The report was based on a meta-analysis of 26 studies. The selected studies involved six different measures of mental health: anxiety, depression, mixed anxiety and depression, positive affect, psychological quality of life, and stress. The median age of the studies' participants was 44 years; the median length of follow-up was six months. On average, study subjects had moderate nicotine dependence and smoked 20 cigarettes a day.

The summary measure used for evaluating the studies' data was the standardized mean difference (SMD) from baseline to follow-up between participants who quit smoking and those who continued smoking.

According to the analysis, quitting smoking was associated with significant decreases in anxiety (-0.37 SMD), mixed anxiety and depression (-0.31 SMD), depression (-0.25 SMD), and stress (-0.27 SMD), as well a significant improvement in psychological quality of life (+0.22 SMD), when compared with continuing to smoke.

The study authors theorize that the ability of smoking cessation to improve mental health may have a biological basis, but they conclude that, regardless of the causal mechanism involved, their analysis shows that "smokers can be reassured that stopping smoking is associated with mental health benefits."-David Carter

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