A new pilot study released by the American Academy of Neurology (AAN) Tuesday further bolsters the case for a link between irritable bowel syndrome (IBS) and certain types of headache, especially migraine.

The researchers studied patients suffering from either migraines or episodic tension type headaches (ETTN) and found that migraine sufferers were twice as likely to also report IBS symptoms when compared to ETTN patients (54 percent vs 28 percent). The flip side of that equation was also confirmed among the IBS sufferers they additionally studied, since 36 percent of IBS sufferers reported migraine, compared to 22 percent who reported ETTN headaches. Lastly, when compared to healthy control subjects, all three groups of sufferers were more likely to have genetic mutations associated with the distribution of the neurotransmitter serotonin, though the specific mutations weren’t identical between groups.

"Since headache and irritable bowel syndrome are such common conditions, and causes for both are unknown, discovering a possible link that could shed light on shared genetics of the conditions is encouraging," said lead author Dr. Derya Uluduz of Istanbul University in Turkey in a statement. According to a 2010 report from the Centers for Disease Control and Prevention, 22 percent of women and 10 percent of men in the general population report having had migraines or severe headaches in the past year. 

There’s steadily growing support for the idea that migraines may share a common bond with not only IBS, but other chronic gastrointestinal disorders such as celiac disease. For instance, a 2006 prevalence study of just over 120,000 people found the odds of developing migraine were 60 percent higher among IBS patients than with healthy subjects. And a 2003 study found that restricting the diets of people with celiac and migraine successfully reduced the symptoms of both, though that study involved only four patients. Meanwhile, according to a 2010 report from the Centers for Disease Control and Prevention, 22 percent of women and 10 percent of men in the general population report having had migraines or severe headaches in the past year. 

For the current research, Uluduz and her colleagues recruited the help of 107 migraine and IBS sufferers each, as well as 53 ETTN and healthy control patients. When looking at the genetics of each group, the migraine and headache sufferers were more likely to possess a mutation to the gene responsible for transporting serotonin, while IBS sufferers were more likely to have a mutation to a gene that regulates our serotonin receptors.

Low serotonin levels are known to be associated with both headaches and certain types of IBS. Additionally, one of serotonin’s many functions is helping regulate our gut-brain axis, a complex system of communication between our digestive and nervous systems that even involves the good bacteria found in our intestines known as the gut microbiota. The researchers theorize that an impaired gut-brain axis may explain the connection between the two conditions, with low serotonin and stress as possible mechanisms. They even go so far as to coin IBS the “migraine of the bowels.”

"Further studies are needed to explore this possible link," said Uluduz. "Discovering shared genes may lead to...future treatment strategies for these chronic conditions."

Genes will likely only be part of the answer. Similarly, serotonin isn’t the only potential culprit when it comes to either condition. For instance, women are consistently more likely to have a history of migraines and worse episodes in general, signaling a possible hormonal connection.

The study findings will be presented at the AAN’s 68th Annual Meeting in Vancouver, Canada, later this April.

Source: Uluduz D, Cakmak S, Ozge A, et al. A Link Between Migraine, Tension Type Headache and Irritable Bowel Syndrome: Clinical and Genetic Indicators. ANN 68th Meeting Abstract. 2016.