ADRA1D and irritable bowel syndrome: Figure 4 shows that the participants in the IBS group carrying more C alleles reported a higher fatigue level, while the trend was the opposite in the HC group. Table 3 presents the significant interaction effect of the number of T alleles of ADRA1D rs1556832 by groups (p = 0.007) on fatigue. Specifically, for each C allele at ADRA1D rs1556832, the fatigue score increased by 3.47 (p = 0.016, 95% CI = (0.65, 6.28)) among the IBS patients, whereas the fatigue score decreased by 4.27 (p = 0.084, 95% CI = (−9.13, 0.58)) in the HC group.