The narrator of The Yellow Wallpaper develops insanity as the story develops. At the beginning of the story, the narrator is just facing depression that arises out of post partum stress and the suppression she is subjected to by her husband, John, and her relatives. Her post partum depression is so overwhelming and is increased by the rest cure prescribed by her doctor and husband. She is separated from her little child, and is subjected to the rest cure treatment. She barely keeps up with the treatment, opposing it due to her rational stance against it. Her husband could not let her engage in any work, including thinking so when she has to write, she even hides her writing from him and their house help. But her condition deteriorates despite the treatment, causing her to move from depressed condition to a psychotic one.
At the beginning of the story, she is only depressed but fairly reasonable as she tells of John’s decision to take her to the house which she thinks is haunted. At the stage, she even questions why the house has remained untenanted and why it was rented out cheaply in spite of its magnificence, considerations which are rational to make. However, after living for some time under the conditions of isolation and denial of work in the house, she begins to have bizarre ideas like her identification of a woman imprisoned inside the yellow wall paper in their bedroom. Traits of insanity show as she peels off the paper in order to liberate the woman. As the narrator’s insanity develops, the imaginary woman preoccupies her mind such that their characters later merge. She gets compulsively dedicated to liberation of her repressed self, in the form of the woman in the wall, and ends up losing her mind completely. Her odd physical activities like peeling the paper of the wall are indications of her deteriorated mental condition.
The narrator reaches the point of total insanity later in the story when she presumes to have liberated the woman from the wall after successfully peeling off the paper. The actions she engages in clearly show that her situation has changed from depression to insanity. For instance, for the first time in the story, she locks the door to block her husband from entering and throws the key away. She then ties herself to the bed and starts to crawl around their bedroom. Upon discovery of her condition, her doctor husband, who has been regarding her as normal before, is shocked to a point of fainting.