It's the few instances of new onset IBD and generally the GI side effects. I'm lucky enough to have a pretty solid GI system that I don't want to risk messing with. I get very anxious with medicine, and my ankylosing spondylitis is sufficiently slow moving on MRI and tolerable enough that I prefer not to use the medicines. I had too many strange side effects whilst on Humira/Remicade such that it scares the crap out of me.