Hello!
I've been looking for this specific fic that I didn't remember the title or the author is. Dean admitted into asylum since he was a kid. I remember he was admitted because he's the only one who saw what happened in the fire that killed his mother (about the yellow eyed demon killed her), but when he tried telling anyone about that, no one believe him and thought it's just trauma. But Dean always said that demon killed Mary though months (or years?) had passed, so John admitted him to an asylum, thinking the shrinks could help his son. John and Sam lived in ignorance, until Sam got vision when he's an adult. But I think they think that's just dream, because I remember they believe about supernatural after Castiel the angel came and "kidnapped" Dean.