My former doctor told me I was depressed, therefore causing my IBS. Only thing is I didn't feel depressed as much as anxious.
About 10 years ago is when I decided to not let my dysfunctional family run my life. I felt better - not as many stomach aches until my car accident 7 years ago. I was lucky to walk away from it, but I got pregnant with my third child 7 months later and have never felt the same.
Make a long story short, yes, trauma can cause IBS to become worse. I'm not convinced my IBS is mostly Psych., since I do deal with GERD's, which can cause more problems without meds. I do believe there is a physcial problem causing IBS, but there hasn't been enough research to pinpoint the problem. There are doctors out there who don't believe IBS is a real problem.
If you can learn how to manage your stress better and make the choice to not allow past or current events to run your life, instead you take of your life, IBS will be easier to deal with.