A systematic review and meta-analysis of observational studies has investigated the change in mental health after smoking cessation compared with continuing to smoke.
Eligibility criteria were longitudinal studies of adults that assessed mental health before smoking cessation and at least six weeks after cessation or baseline in healthy and clinical populations.
26 studies that assessed mental health with questionnaires designed to measure anxiety, depression, mixed anxiety and depression, psychological quality of life, positive affect, and stress were included.
Follow-up mental health scores were measured between seven weeks and nine years after baseline.
Anxiety, depression, mixed anxiety and depression, and stress significantly decreased between baseline and follow-up in quitters compared with continuing smokers: the standardised mean differences were anxiety -0.37; depression -0.25; mixed anxiety and depression -0.31; stress -0.27.
Both psychological quality of life and positive affect significantly increased between baseline and follow-up in quitters compared with continuing smokers 0.22 and 0.40, respectively.
There was no evidence that the effect size differed between the general population and populations with physical or psychiatric disorders.
In conclusion, smoking cessation is associated with reduced depression, anxiety, and stress and improved positive mood and quality of life compared with continuing to smoke.
The effect size seems as large for those with psychiatric disorders as those without.
The effect sizes are equal or larger than those of antidepressant treatment for mood and anxiety disorders. ( Xagena )
Taylor G et al, BMJ 2014;348:g1151