Some major themes in "Speak" by Laurie Halse Anderson include communication, depression, female empowerment, gender roles and sexuality. Anderson said the book is about more than just rape, but is about the depression it causes. Depression explains all the struggles of the protagonist, Melissa, as she deals with the other themes.
On the surface, the theme of communication appears in Melinda's silence. However, communication appears in other forms: sticky notes, notebooks and letters passed between students, notes on the chalkboard, and remembered and overheard spoken and telephone conversations. Melinda's communication is nonverbal until the end of the novel, when the title and theme come to fruition in the implication, but not explicit inclusion, of Melinda's revelation of her story.
The theme of communication connects with female empowerment when Melinda refuses to give a speech. Through standing up for her right to not speak, she likens herself to the suffragettes who fought for women's rights to speak. Female empowerment, or lack thereof, emerges in the gender role and sexuality themes evident in the Marthas, in the avoidance of the cat-calling janitor and in Melinda's mother's Thanksgiving dinner. In addition, Melinda's struggle with communication echoes the gender roles that leave women voiceless. Melinda dislikes the sexuality of her classmates, and her concern that revealing her sexual attack will make her attacker more appealing reaffirms the themes of gender roles and sexuality.