What does Judaism say about therapy and mental health? Is it a lack of faith to need it?

Needing help is not a lack of faith — it is taking the body and mind God gave you seriously. We are commanded v'nishmartem me'od l'nafshoteichem, to guard our lives carefully, and the same tradition that tells you to see a doctor for a broken arm tells you to get help for a hurting mind. Going to therapy is not betting against God; it is using the healers God put in the world.