Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses showed that the upregulated genes were closely related to system development, the extracellular region, regulation of molecular function, and the interleukin-17 pathway (Figure 4A, 4B), whereas the downregulated genes were closely related to RNA processing, the nucleolus, signaling receptor activity, and the nicotine addiction pathway (Figure 4C, 4D). This evidence concerns the gene IL17A and nicotine dependence.