There are notable genetic correlations between irritable bowel syndrome (IBS), and mental health disorders such as anxiety, depression, bipolar disease, and schizophrenia, a new study reveals.

Researchers from the University of Oslo and the University of Bergen in Norway, and the University of California in the US say their findings shed more light on the complex relationship between our brains and our guts, and could open up more possibilities for the treatment of IBS.

Using a statistical method recently developed by one of the team, the researchers analyzed data on 53,400 people with IBS and 433,201 controls, looking for genomic risk loci – specific locations within DNA sequences where the genes can suggest an increased risk of a particular heath problem.

As polygenic traits, IBS and mental health are heavily influenced by a variety of genes. In this case, a number of them were found to be shared. The researchers identified 70 unique loci where gene variants indicate risk of IBS, with 7 of those same genes also associated with generalized anxiety disorder, 35 with major depression, 27 with bipolar disorder, and 15 with schizophrenia.

"We found extensive polygenic overlap between IBS and psychiatric disorders and to a lesser extent with gastrointestinal diseases," write the researchers in their published paper.

Almost 1 in 10 people worldwide are thought to be living with IBS, which can lead to cramps, pain, and diarrhea. While its causes are unknown, it's generally considered to be linked to the way the brain responds to nerves in the gut.

This new study backs that up on a genetic level and gives researchers and health professionals new gut-brain links to examine. The research also sheds light on pathways giving rise to IBS that are unrelated to the nervous system, which could offer alternate approaches to treatment.

On this occasion the researchers didn't look any deeper into any mechanisms related to the genetic overlap, but they suggest intestine inflammation may cause bacteria to leak into the blood and make their way to the brain, which can lead to behavioral and cognitive changes, and might explain the high co-occurrence of IBS with psychiatric disorders.

Scientists are continuing to unpick the way our brains and bellies are linked – from the way that a better education protects your gut, to how certain kinds of bacteria are associated with the development of Alzheimer's.

"This expands our understanding of the genetics of IBS and where IBS lies in relation to gastroenterological and psychiatric diseases," says Markos Tesfaye, a postdoctoral fellow from the Institute of Clinical Medicine at the University of Oslo.

The research has been published in Genome Medicine.