Re: Change in mental health after smoking cessation: systematic review and meta-analysis
On the subject of causation, I would like to point out that there are multiple plausible and relevant factors which are easily overlooked when interpreting the results of a study pertaining to such an emotinally laden topic. Some of them might in fact be overlooked simply because they seem too obvious.
For example, metacognitive abilities and personality traits like delayed gratification or neuroticism are well known to affect both addictive behavior and the development of mood disorders. A person adversely affected by such background factors would seem less likely to both recover from adverse life events and to cease smoking, even controlling for anxiety, etc, at the beginning of a study.
Or from another angle, even if cessation really does causally affect mood, it still matters whether the causation is direct or mediated by an intermediate variable. One obvious such candidate variable is freely disposable income: a pack a day is nowadays rather an expensive habit. Unlike in the case of exercise as the mediator, in this case the most effective intervention would also not seem to be medical, but rather fiscal.
Competing interests: 2+ packs of Camel per diem.