Honestly, I'm not sure.
Crohn's Disease (an autoimmune disease that is very similar, but MUCH more severe than IBS) runs in my family, appearing in every generation for at least the past 5 generations. I'm almost guaranteed to get it at some point in my life. My dad has it, and I fear it incredibly because I see his .
I am lactose-sensitive, with flare-ups of intense intolerance at times. I have other autoimmune diseases (severe psoriasis, beginnings of arthritis, mild restless leg syndrome), and where there's one, there's often several to come. IBS is also an autoimmune disease.