What is the exact mechanism behind stress-related stomach problems (e.g. dyspepsia)?

There are a few different mechanisms that could contribute to stress-related stomach problems. For example, when you're stressed out, your body releases more of the hormone cortisol. Cortisol not only contributes to the "fight or flight" response, but it can also have negative effects on the digestive system.

Another possible mechanism is that when you're stressed, you might be more likely to eat unhealthy foods or drink alcohol, which can lead to stomach problems. Additionally, stress can cause changes in the gut microbiota that might lead to inflammation and digestive problems.