anxiety and stress
"I took 10mg Celexa (increased to 20mg) for a year after experiencing panic attacks and generalized anxiety for 3 years.  My anxiety affected my stomach the worst, I'd have trouble eating anything without getting a stomach ache or diarrhea. It's as if all the butterflies in my stomach ate my food for me.  After taking Celexa my anxiety disappeared completely and my stomach went back to normal.  However, I stopped taking it due to the side effects.  I had no more sex drive, and had difficulty feeling any emotions, or at least to the extent I felt them before.  I felt foggy and not myself.  Soon as I went off it I had panic attacks again but felt more clear."