The term Folk Art has no currency in Europe. They were never without an academy and they never learned to value the junk that Abbey Aldrich Rockefeller did. The very term Folk Art in Europe refers only to what can be seen as a group phenomenon such as Swiss decorative doilies or plates or Yugoslav paintings on reverse glass.
They do use the term Naive Art to describe the above two categories and, in fact, occassionally there are examples of Art Brut art even within these categories but the important information to be gleaned here is that although the genesis of the term Art Brut was specifically M. Dubuffet, there were several European psychiatrists (most notably Morganthau, Prinzhorn, Kris and Navratil) who themselves collected the works of schizophrenics. Some of them came to Dubuffet's attention most notably Wolfli, Carlo, Mueller, Aloise.
The publication of books by the psychiatrists mentioned above respectively in 1921, 1922, 1952 and 1963 began a slow but deepening interest in this material first, on the part of artists and writers and then on the part of a very few museum people, most notably Harry Szeemann.
It should be noted that, although one is told that the initial inspiration for Dubuffet's enthusiasum was Adolf Wolfli in 1945 (Wolfli died in 1930) about half the artists in Dubuffet's Collection de l'Art Brut which is now housed in Lausanne, Switzerland were not clinically insane not institutional. As far as we know only three of the American Art Brut artists (Ramirez, Podhorsky and Wentworth) were institutionalized but then we have no record in America of any psychiatrist finding any art.
In sum we can use the term Self-Taught Art to refer generically to just that and we can perceive a subset of that (just American) which is, by force of habit, called Folk Art. Another subset is called Art Brut and that category has some Americans and some anything else (one of the Art Brut artists I represent is Japanese).