Among others, Chromogranin A has been negatively correlated with gut microbial diversity (Sundin et al., 2018; Zhernakova et al., 2016) and has been shown to be increased in irritable bowel syndrome (IBS) patients as well as to correlate with abdominal pain in IBS (Ohman et al., 2012). This evidence concerns the gene CHGA and irritable bowel syndrome.