There is no known specific cause, but some experts suggest people who suffer from IBS have a colon that is more sensitive and reactive to certain foods and stress. (The disorder is also known as spastic colon.) Although IBS can be painful and uncomfortable, it is not permanently damaging to the intestines, nor does it cause other gastrointestinal diseases.
People with IBS frequently suffer from anxiety and depression, which can worsen symptoms. That’s because the colon is in part controlled by the nervous system, which responds to stress. Evidence also suggests that the immune system, also responding to stress, plays a role. IBS can also make you feel more anxious and depressed.
https://adaa.org/understanding-anxiety/related-illnesses/irritable-bowel-syndrome-ibs
