I am certain it could Jen. Doctor's appointments, especially with the psychiatrist, can be very stressful. Two hours is not too short for physical symptoms to begin either in my experience. Evie does not have IBS however she does have serious digestive problems and she can have nausea, vomiting, diarrhea and so on within a few minutes of having a difficult or stressful experience. Additionally if he has already started the new medications those could be bothering him as well. I do hope he is feeling better soon.