Link found between inflammatory bowel disease and depression

A new study from Keck Medicine at the University of California (USC), in the United States, has found that patients diagnosed with inflammatory bowel disease were nine times more likely to develop depression than the general population. In addition, their siblings who did not have IBD were almost twice as likely to develop depression, the researchers report in the Journal of Gastroenterology and Hepatology. By contrast, patients with depression were twice as likely to develop IBD, and their siblings without depression were more than one and a half times more likely to develop IBD.

“This research reveals a clinical overlap between the two diseases, and is the first study to investigate the bidirectional association between IBD and depression in siblings,” said study co-author Dr. Bing Zhang, a gastroenterologist at Keck Medicine.

Zhang and his colleagues analyzed data on more than 20 million people from the Taiwan National Health Insurance Research Database, which contains comprehensive medical information on more than 99% of Taiwan residents. For 11 years, they followed patients with IBD or depression and their siblings without either condition, and compared the occurrence of depression or IBD with a control group of people without either condition but with similar age, sex and socioeconomic status.

Zhang hypothesizes that there are many factors that may contribute to the bidirectional nature of the disorders, including environmental stressors, the gut microbiome (made up of bacteria, fungi, and viruses), and genetics.

“The finding that people with IBD are more prone to depression makes sense because IBD causes ongoing gastrointestinal symptoms that can be very disruptive to a patient’s life,” he said. And the elevated risk of depression among siblings of IBD patients may reflect caregiver fatigue if siblings have a role in caring for the patient.”

What surprised the researchers was that depressed patients were prone to inflammatory bowel disease. Zhang speculates that this discovery may have to do with what is known as the gut-brain axis, a scientifically established connection between the gastrointestinal system and the central nervous system, made up of the spinal cord and the brain.

brain swelling

For example, he notes, inflammation of the brain, which plays a role in depression, may be related to inflammation of the gastrointestinal tract, a hallmark of IBD.

Researchers aren’t sure why siblings of patients with depression are more likely to be diagnosed with IBD. Zhang surmises that there may be a shared genetic susceptibility to either disease that presents differently in family members.

Zhang hopes that the study results will encourage health professionals to consider both family history and the relationship between gastrointestinal and mood disorders when evaluating or treating patients with IBD or depression.

Through further research and a better understanding of the gut-brain axis, he plans to harness the new connection between conditions to improve the prevention, diagnosis and treatment of IBD and mental disorders.