I suffer from IBS as well and out of all the things that flares up my IBS, stress is a prominent one. Reading research papers, its been seen that gut biome changes based on stress - look up gut-brain connection, theres been a few books written about it as well.

Its a fairly new thing - from about 15 years back. Nowadays one of the treatments that a gastroenterologist could recommend if they have exhausted everything else is low dose anti-depressant.

Key is to identify what is causing stress and treat that