The rs1800795 is a functional polymorphism affecting IL6 gene transcription, and the minor allele is associated with significantly lower levels of plasma IL-6 (Fishman et al., 1998).
Barkhordari et al., 2010 report no association with irritable bowel syndrome for a second, intronic SNP (nt565, SNP number not given), but did see overrepresenation of a two-SNP haplotype in patient group.
Negative results: A previous study on pain in lung cancer (Reyes-Gibby et al., 2007) found no significant associations, possibly due to small sample sizes. Rainero et al., 2003 reported no significant association with migraine.