Not specifically mental health (or maybe ), but something deep and interesting about (a special) human relationship(s):
Let the right one in (Låt den rätte komma in) 2008, the Swedish original version
(sorry I don't have enough posts to paste an Imdb link in)

(Yes, it has horror-elements and it is creepy sometimes, but it's just not a horror movie and isn't at all about what it seems like and what they did with the US remake.... watch it with original audio and English subtitles)

I could relate so much, I wonder if similar people will feel the same if they see the movie