Abnormalities in multiple systems are observed in both smoking and suicide, including serotonergic and receptor-linked signaling pathways (Pandey, 2013), inflammatory mediators (Rom et al. 2013), and neurotrophins and neurotrophin receptors. Brain-derived neurotrophic factor (BDNF) is a much studied member of the neurotrophin family, and genetic variation in the BDNF gene is strongly associated with smoking initiation (Liu et al. 2010; Thorgeirsson et al. 2010; Tobacco Genetics Consortium, 2010; Breetvelt et al. 2012). Further, smoking quantity, severity of nicotine dependence and smoking cessation affect BDNF expression levels (Bhang et al. 2010; Jamal et al. 2015; Zhang et al. 2016). Thus, BDNF expression in the brain is regulated by neurotransmitter systems involved in nicotine use.
