PPARA and nicotine dependence: As shown in Fig. 6E, the KEGG enrichment analysis of the top 20 (filter the pathway entries corresponding to PopHits ≥ 5, and sort from largest to smallest according to the -log10P-value) was mainly enriched in p53 signaling pathway, PI3K-Akt signaling pathway, MAPK signaling pathway, PPAR signaling pathway, nicotine addiction, etc. The DEGs contained in the Top 20 signaling pathways of the KEGG enrichment analysis are shown in Supplementary Table 3.