There is definitely a big impact on the gut by those drugs, in my experience... For me it was extremely negative. My digestion is much worse since then. I also gained weight, partly because severe carb craving like I've never experienced before (esp on paxil, but I tried them all..).. Plus, my stomach always hurt so all I wanted to eat was noodles and bread...
I kept telling my doctor(s) that I wasn't depressed; I felt like I was always walking around w 50% of the flu, persistent digestive problems, I always got sick, etc. They just kept telling me, "Oh, you have a somatic depression"... Then I got mono and took a nosedive....
That chapter (~15-18 yrs ago) is my biggest regret for managing this illness.. "First do no harm" is seriously BS, and buyer beware is everything.