I am an art therapist. The term "art therapy" or "Art Therapy" is specific to the visual arts (drawing, painting, sculpture, etc.). I think the term "visual arts" should be added to this definition.
It cannot be made plural.
One may correctly say "arts therapies" (notice the "s" is on both words), which would then refer to all the different disciplines in which the arts are used in therapy. For instance, there is music therapy, poetry therapy, drama therapy, and others. Collectively they are referred to as "arts therapies", "creative arts therapies", or "expressive therapies".
I think the plural should be eliminated, and there should be links to the other arts therapies added.
Sorry, but I do not have the skills to make these changes myself.