I think one of the psychological aspects that is worthy of discussion is the character, nature and motivation of Roderick Usher. It is never precisely clear whether he has deliberately interned the body of his sister knowing that she is still alive or if it was a genuine mistake. However, a big issue is whether he and his sister are actually cursed or if his 'illness' is a result of his own choice.
The evil in the story is a psychological phenomenon, and Poe creates this atmosphere of evil throughout the story. In his description of the house, the narrator calls it a "mansion of gloom". Poe also depicts evil in the characters of Roderick and Madeline. Roderick's "ghastly pallor" and Madeline's description as ghostly, floating through the rooms, makes our skin crawl. As most of us would do, the narrator tries to find reasons for what is happening, but he's unable to sustain any logical conclusions for what's happening to Roderick, Madeline, and the house. As the story progresses, the supernatural elements really kick in, and I think forces of the supernatural scare many of us because things that shouldn't happen do happen, and we have no control over them. We fear what we can't explain or don't understand, so the reader is as psychologically affected as the narrator by what happens. This is what a good scary story should do, and Poe was one of the best writers to be able to do it.
The most interesting aspect of this story, for me, is the character of Roderick. He is obviously mentally ill, so I would love to have the story told from his perspective to see into his mind a bit more. Because the narrator is his friend who comes to visit, we don't see much into the mind of Roderick. Also interesting to me is the house itself. It is a horribly oppressive house with darkness and dreariness everywhere! It is no wonder the two Ushers are depressed and/or mentally ill. Then environment isn't conducive to happiness and joy!