Who is Dr. Madden from Next to Normal and what is their importance?

Dr. Madden is Diana's psychiatric therapist. Confident and mature, he is described as "ageless." At first he tends to baffle Diana with scientific jargon, but as he warms to her and gains more insight into her condition, and her interaction with her condition, he becomes less formal and more human. He tends to be unquestioningly confident in his abilities and treatments, and is somewhat shocked when Diana seems to repeatedly reject them. At the conclusion of the narrative, however, he has come to realize that his is not the only way; there are other ways, other methods, to approach and embrace the healing process, as manifest for him in the song "Light."