Characters throughout the book take strides to hide their mental illnesses. After being labeled a “freak” by a classmate when attempting to share disordered thoughts, Theodore Finch learns to keep his feelings and moods to himself. Amanda Monk, a popular cheerleader, attends a suicide support group but swears Finch to secrecy. Violet hides the extent of her grief. The book shows the ultimately disastrous consequences of silence surrounding mental health.

Finch is the primary vehicle through which this theme is explored. On the surface, he is extremely intelligent, has achieved early acceptance to NYU, and is a gifted musician and lyricist, but in reality he struggles with symptoms of agitation and depression. His narratives indicate that he has experienced atypical thoughts and feelings since childhood but has refused to disclose them because of the way he might be perceived. Specifically, he mentions having the ability to “see” headaches to a friend, Gabe Romero, when the two are in eighth grade. “Roamer” subsequently tags Finch as a “freak,” leading the young man to experience marginalization by his peers. Finch writes about his long periods of being “Asleep” (clinically depressed) and “Awake” (manic). He makes heroic strides to remain “Awake” by running for miles every night and composing lists of methods to keep himself from falling asleep.