I think anxiety is pretty common with UC. I didn't leave the house for much other than work when I was really sick...I didn't want to poop my pants in a store! I was diagnosed with postpartum anxiety shortly after my son was born, but by that time I was also in the midst of my first (really bad) flare, but hadn't been diagnosed yet. I'm sure the UC made my anxiety worse than it would have been, but I think I would have had anxiety issues regardless.
Anyway, I've been on Zoloft since my diagnosis of PPA, and I've chosen to stay on it for the next little while, because it made a huge difference for me and I'm taking the lowest possible dose. I've got some potentially stressful things coming up in the next few months and I'll try going off of it once that has passed, but if it turns out I start having issues with anxiety again, then I'll go back on it. I'm really glad that I was on it when I was diagnosed with UC. I really think it helped me deal with the diagnosis.
Symptoms began in November 2008, ~4 weeks after giving birth to my son.
Eased for ~3 weeks in December, possibly b/c of probiotic use?
Returned in January 2009 (with a vengeance), diagnosed with pancolitis on January 30.
Currently taking Asacol (400mg 4 pills 3x daily), Rowasa nightly, Culturelle probiotic, and Zoloft (25 mg).