Kawakami et al34 found that in asthma exacerbation triggered by emotional stress, functional SNPs in the stress-related μ-opioid receptor gene (OPRM1; A118G SNP, rs1799971) may induce eosinophilic inflammation in mouse lungs by increasing the generation of effector Th2 cells in peripheral lymph nodes. Here, OPRM1 is linked to asthma.