As an exploration of duality in women, “Two Sisters of Persephone” is significant to Plath’s place in the literary canon. She was widely believed to have undiagnosed bipolar disorder. A famous entry from her journal reads, “It is as if my life were magically run by two electric currents: joyous positive and despairing negative—whichever is running at the moment dominates my life, floods it.” The essences of both “sisters” in the poem were within the poet; duality was a reality of her daily life. In fact, the controversial link between mental illnesses and creative fire has been called the “Sylvia Plath Effect” (Smith Bailey, Deborah. “The 'Sylvia Plath' effect.” American Psychological Association, 2003).

The concept of duality continues into the divide between Plath’s creative youth and her marriage to the poet Ted Hughes. She began publishing her poetry very young, and writing was an integral part of her young identity. This poem was written in the same year as Plath’s marriage to Hughes; the two sisters of the poem are a metaphor for the two stages of Plath’s life and the two potential roads she might take.