Anxiety all by itself is very vague; please give more details if you can. What triggers it, etc.
Anxiety as a state of being is caused by fear, doubt, and worry. These all stem from ignorance (not knowing). So, to treat it, you simply have to study what you fear. Don't run from it.
By understanding the problem, you learn how to deal with it.
If it is social anxiety, which is pretty common nowadays, that is a manifestation of low self-esteem. You can address this with a Sun Square or other magickal workings as you see fit.