Charlotte Perkins Gilman (1892)
One of the main themes of "The Yellow Wallpaper" is nervousness. In the 1890s, it was widely believed by psychologists and sociologists that modern life was so stressful that it overloaded the nervous system and caused people to break down. Often these ideas were gendered; it was assumed that women had more fragile nervous systems and became neurotic more easily.
Gilman was arguing against the "rest cure," which required anxious or depressed women to be cooped up all day and do as little as possible in order to "calm their nerves." Gilman knew from personal experience that this "cure" only increased a person's nervousness. In her own time, Gilman was known better as an economic thinker than as a storyteller. Her work was focused on the way in which women were barred from participating in public activities (activities that took place outside of the house, like careers and politics).
She believed that nervousness in middle class women (there are a lot of outdated psychological terms for this, like neurasthenia and hysteria) was caused by a lack of opportunity for these women to do out and do things and use up this energy. If a person is stuck at home, Gilman argued, this excess energy will always find something to latch onto, and the nervous person can become unhealthily fixated or obsessed with something; in Gilman's story, this 'something' is the pattern on the wallpaper in the room that she is not allowed to leave.