My wife has Chron's and she was told it is genetic but does not manifest in everyone and can skip many generations. But, some studies show that smoking can cause it to manifest. As well as birth control, but that isn't what this thread is about.
Wiki also shows that smokers are 3 times more likely to have it manifest.
http://en.wikipedia....Crohn's_diseaseI guess stress can cause a flareup, so quitting smoking may cause a breakout of inflammation. But, once it is done, and you are no longer stressed out, you will have a lot less of a chance of another flareup.