It’s rare the someone gets over their lifelong anxiety/depression. That has happened to me. And how that happened to me and for me matches what the Bible says, which is “You will know the truth and the Truth will set you free.” This is not proof of God. But it’s huge evidence for His existence.
Let’s say you were wanting to be cured of a serious disease and you happened upon an ancient book that claims to cure your disease. You try the treatment in the book. And you get entirely well. You would give the book and it’s author lots of credibility, right? Same thing.