The exact cause of IBD is still unclear. Researchers believe an unknown factor or agent triggers an abnormal reaction by the body's immune system. The most common signs of the diseases are diarrhea and abdominal pain. IBD tends to run in families and is more likely diagnosed in young adults. People of Jewish heritage, particularly Ashkenazi Jews who are of Eastern European descent, have an increased risk of developing the disease.

Further analysis revealed that of the 163 genes associated with IBD, 110 are associated with Crohn's disease and ulcerative colitis, 30 are specific to Crohn's, and 23 are specific to ulcerative colitis. For 29 of these new and previously reported specific gene locations, the researchers observed genetic differences between people with IBD that predict changes to the protein structure. Among the remaining 134 genes, genetic variants associated with the disease did not cause changes in the structure of the encoded proteins and many of these variants may change the levels of gene expression. These clues will help investigators determine the specific genes, alleles and altered pathways responsible for increasing a person's disease risk.

"Performing the meta-analysis on these large datasets provides the statistical power and integrity to confirm the associations of these genes to IBD and identifies gene variants that until now, were only suspected to overlap with other inflammatory diseases," said Dr Judy H Cho, lead author and professor of medicine and genetics and director of the Inflammatory Bowel Disease Center at Yale School of Medicine.