Second, chronic cigarette smoking enhances tachykinin synthesis, stimulates neurogenic substance P release (Kwong et al., 2001; Xu and Xu, 2010), and accelerates the thinning of the brain’s cortex (Karama et al., 2015), which is one factor resulting in peripheral neuropathy (Richardson et al., 2009), such as axon loss and demyelination. This evidence concerns the gene TAC1 and peripheral neuropathy.