We also noticed that some dependence-associated DEGs could be induced by both morphine and heroin, e.g., among DEGs upregulated in the IE phase, Dapk1 and Plekhf1 were correlated with psychological dependence, while Dusp12 and Pim3 were associated with physical dependence after exposure to both morphine and heroin. This evidence concerns the gene DAPK1 and substance dependence.