I don't know that people with IBS are more prone to headaches than others.I have migraines, I have IBS and they do not seem to track much with each other at all. Although both will come up right after an allergy shot, because histamine has been implicated in migraines and diarrhea...but that is a third thing that triggers both. If one or the other goes off at another time, it does not seem to matter. When I am not on allergy shots I usually do not get migraines or even other headaches at all and the IBS hit during one of those in between times.So it varies.However, pain is a physcial stressor. Stress of any kind (physical, social, emotional, etc) does not help any disorder, disease, pain, etc. The physical stress of the IBS or the physcial stress of the headache could certain be a trigger for the other in some people.The which triggers what may depend on which thing is more triggered by physical stress.