This is like a two sided sword... Depressants are supposed to bring you up, while anti-anxiety meds are supposed to calm you down.. If both Anti-Depressant and Anti-Anxiety medications are used in conjunction, they equal out and seem to treat either condition slightly better..
Some Anti-Anxiety medications treat both, but if you have Anxiety and are just taking an Anti-Depressant, I would talk to your Pharmacist regarding what your current medication treats.. I've been taken off Anxiety meds and put just on Anti-Depressants, simply because the Dr's don't know enough Like the Pharmacists, and assume it will treat both..
I hope this post has helped some and that I haven't rambled on too much..