Outside of the feminist perspective provided above regarding the oppression in Gilman's "The Yellow Wallpaper", one could look at the oppression both the environment and mental defect have upon the unnamed protagonist of the story.
First, the room alone oppresses the protagonist. She finds it impossible to become well again (she is suffering from Post-partum depression) in a room as littered with evidence of past horrors. The scratched floor, marks in the bed posts, and (above all else) the wallpaper. The room alone oppresses the protagonist.
Outside of the environment, the post-partum depression oppresses the protagonist. Her inability to pull herself out of this mental deficiency adds to her oppression. No one really helps her overcome the PPD. Instead, she is left to fight against it on her own. The fact that the PPD oppresses her mentally speaks to the fact that she is driven even further into insanity.
In order to answer this question we should consider the feminist approach in literature. According to the feminist methodology, the traditional roles of women are constrained to the patriarchal order, in which masculine ways of thinking are privileged. Furthermore, this approach allows us to identify the misrepresentations of women’s role in society and helps us to look for social misconceptions that treat masculine behavior as a norm and feminine viewpoint as a deviation.
In the case of “The Yellow Paper”, in order to treat her wife’s postnatal depression, the narrator’s husband, John confines her to a room in a certain summerhouse. He also forbids her to execute any task, including reading or writing. This attitude exemplifies two distinct roles: the narrator’s husband, who personifies order, authority, and law, and the narrator who has no other choice but to be restraint to the role of good mother and wife, or as the feminists would call the angel in the house.
However, the narrator seems to defy the traditional feminine roles and becoming hysterical is her way to revolt. The wallpaper is full of symbols reflecting the narrator’s wish for defiance of the patriarchal order. For instance, the woman she sees behind the wallpaper is her own image trying to free from the oppressor, in this case, the husband, John.
Conclusion, if we place John at the discursive centre, as someone who represents the patriarchal authority, we consider the narrator as being ill. However, taking into account the narrator’s point of view, as a possible victim of the patriarchal system, we may say that her illness is a way to defy the traditional women roles in society.