The central conflict that is present in Edgar Allan Poe's "The House of Usher" involves the unstable conditions of Roderick Usher.
In this Gothic thriller, Roderick Usher suffers from internal conflicts. These conflicts are composed of three components: his sensory sensitivity, his fears, and his anxiety. Although the terminology was unavailable to Poe in his time, Poe describes in Usher the psychological condition of hyperesthesia, which is an extreme sensory sensitivity. For instance, he is extremely affected by such things as light, sounds, smells, and tastes. This "constitutional and family evil" involves Roderick's suffering from "a morbid acuteness of the senses":
...the most insipid food was alone endurable; he could only wear garments of a certain texture; the colors of all flowers were unendurable; his eyes were tortured by even a faint light.
There are also sounds that seem "peculiar" to Roderick. Some of these sounds are made by stringed instruments, and their vibrating sounds cause Roderick to become fearful.
As his fear grows, Roderick becomes terrorized by his acute anxiety. Because of this anxiety, Roderick has frightening anticipations of going mad and dying. In fact, as the narrator makes efforts to relieve his friend's fears and melancholy by engaging in painting with him and by listening to Roderick's dirges and unusual interpretive renditions of the music of Von Weber, he perceives:
...a full consciousness on the part of Usher of the tottering of his lofty reason upon her throne.
That is, Roderick Usher himself realizes that he is becoming mentally unstable. Usher's instability also becomes apparent as he tells the narrator that the old house itself is making odd sounds.
Roderick also suffers from hypochondria, the fear of illness. The Usher family has virtually wasted away, and only he and his sister remain. Roderick is especially worried about his sister's illness and the fact that if Madeline Usher dies, his only remaining relative will be gone. He is also probably anxious about his own health since she is his twin sister.
As he tries to cheer Usher by painting and reading with him, the narrator specifically alludes to hypochondria in his comments upon Roderick's painting:
...there arose out of the pure abstractions which the hypochondriac contrived to throw upon his canvas, an intensity of intolerable awe.
These unstable conditions of Roderick Usher contribute to the internal conflicts which develop the strange narrative and its horror in Poe's Gothic tale.