I found this brief article insightful. I have always felt that math anxiety does not just materialize but comes from messages that children receive that they should be anxious. It is helpful to know that this is one source. The next step is figuring out how to address parent math anxiety so they do not pass it onto their children.
One resource I recommend to parents is YouCubed.org by Dr. Jo Boaler. She provides many practice tools and suggestions to help students learn math in ways that do not produce math anxiety.