Indeed, in IBD patients, the μ-opioid receptor (MOR) is overexpressed in mucosal T-lymphocytes and monocytes, and the administration of low dose Naltrexone (LDN) would appear to upregulate the endogenous encephalin and endorphin levels and to have a positive modulatory effect on the MOR [90]. Here, OPRM1 is linked to inflammatory bowel disease.