We have been investigated genetic influence on one’s smoking behavior, on genes related to neurotransmitters of dopaminergic reward pathways17-19 and inflammation.20 The present study was conducted because the TPH gene codes for a primary enzyme in the biosynthesis of serotonin, and its genetic variation was meaningfully able to alter the risk for smoking dependence, and two closely linked variants in intron 7 have been studied extensively.5,9-12. The gene discussed is TPH1; the disease is nicotine dependence.