It's hard to tell which drug is doing what but my social anxiety has slightly decreased. Lithium was the lastest addition, I am on Zyprexa, Xanax and Lunesta (to sleep); Lithium was added a few weeks ago at a tiny dose (300mg) and we've been gradually increasing it. I am extremely sensitive to medications so everything I go on we have to try a small amount first to check for side effects before we raise it.
I probably haven't been on Lithium long enough to answer your question. I think it has seemed to help my anxiety issues in combination with the other drugs. Though my doc did say that after the Lithium gets me stabilized we can probably begin decreasing the other meds - so I guess she's thinking it will take care of the anxiety too.