The "reported rates" are a different matter ~ I have a problem with the Apostolic Charismatic Church of the First Born because they don't use doctors (except to set broken bones); some, but not all, Plain Church people can have a similar problem. Even worse, some of the First Born actually live in Amish communities, dress like the Amish, live like the Amish, but keep their own separate customs ~ very strange bunch.
They also don't have the pacifist standards of the Amish.
The causes are not always physical/chemical. If they were, psychologists would be out of business.