In psychiatric patients, smoking is associated with higher severity of depressive and anxiety symptoms, and with slower recovery, but only when smokers are nicotine-dependent.

Current smoking and higher number of smoking years are associated with higher levels of serum BDNF, and this is independent of the BDNF genotype. Nicotine dependence itself is not associated with a further increase or decrease of serum BDNF. Longitudinal investigations that address changes in serum BDNF in incident smokers and/or in quitters may be useful to understand the association of smoking with BDNF.

A young age at smoking onset is associated with a shorter time to first onset of an anxiety disorder. This study with psychiatric patients extends previous findings in general population samples that smoking and depression and anxiety disorders are associated.

In patients with a current diagnosis of depression or anxiety, the relationship between nicotine dependence and symptom severity may be moderated by BDNF Val(66)Met. These results suggest that inherent genetic differences may be crucial for the worse behavioral outcome of nicotine, and that Val(66)Val carriers may benefit most in mental health from smoking cessation.