Several factors can affect the digestive system, but the exact cause of IBS-D is unknown. People may have IBS-D for more than 1 reason, and those reasons can be different for every person.
Ask your doctor what might be causing your IBS-D symptoms. IBS-D could be a result of 1 or more possible causes:
Explore the possible causes of IBS-D. Watch the video to get a closer look.
Some studies suggest that an imbalance in the usual numbers and proportions of normal healthy bacteria in the digestive system may be found in people with IBS-D. Your digestive system has trillions of bacteria and microorganisms, collectively called the microbiota, that are constantly working to keep your body functioning normally.
The microbiota help you digest and absorb food and work with your immune system as a barrier against other microorganisms that can cause disease. A study of over 100 people with IBS showed that 73% of people with IBS had an imbalance in their gut microbiota, compared with only 16% of healthy people. An imbalance in the microbiota can be related to genetics, infection or disease, anxiety, diet, drug use, and other causes.
There is a 2-way communication system between the brain and the digestive system, known as the gut-brain axis.
Normally, signals go back and forth between the brain and the digestive system to help your brain and body know when you have eaten enough, when to start digesting food, and when to have bowel movements.
Changes in these signals can cause problems on either the digestive or brain side, which may lead to stress, anxiety, depression, or symptoms such as pain or diarrhea.
Activation of the immune system can cause inflammation that might result in symptoms of IBS-D.
Your immune system is your body’s defense against disease. But if your immune system takes action in your digestive system—maybe because of an infection or stress—the lining of the digestive tract can become irritated and inflamed, causing pain and diarrhea.
Certain genes associated with the immune system, inflammation, digestion, and psychiatric disease may be linked to IBS. Factors such as substantial stress experienced in early childhood could also play a role.
People with family members who have IBS are more than twice as likely to develop IBS themselves.
Many people with IBS-D feel depressed or anxious, but it can be difficult to determine if these feelings are a cause or a result of IBS-D.
Some factors associated with IBS-D can cause depression, anxiety, or other mood disorders. While other studies show that stress may cause changes in the gut microbiota and contribute to the symptoms of IBS-D.