Short tandem repeats in the CNR1 gene were reported to be associated with the vulnerability to irritable bowel syndrome (Park et al., 2011; Jiang et al., 2014), multiple sclerosis (Ramil et al., 2010; Rossi et al., 2011, 2013), schizophrenia (Ujike et al., 2002; Martínez-Gras et al., 2006), and substance use disorders (Comings et al., 1997; Zhang et al., 2004; Ballon et al., 2006). Here, CNR1 is linked to irritable bowel syndrome.