Holden's younger brother Allie died of leukemia when he was eleven years old and Holden was thirteen. Allie's death significantly affected Holden psychologically and he has never healed from the traumatic incident.
One effect that Allie's death has had on Holden concerns his inability to move on and accept the transient nature of life. Psychologically, Holden struggles to live in the moment and desires to stop time from moving forward. He desperately wishes that he could rewind time and relive the moments when Allie was alive and healthy. In addition to Holden's inability to accept the passage of time, he also becomes obsessed with death. For an adolescent with the rest of his life ahead of him, Holden certainly thinks a lot about death. Holden pretends that he is dying, replays the memory of Allie's death, and contemplates suicide.
Allie's tragic death also adversely affects Holden's psychological health as he struggles with severe depression and psychosis. Holden experiences symptoms of these two psychological disorders throughout the novel as he struggles with self-esteem issues and is completely delusional at times. Holden also experiences hallucinations, engages in dangerous, risky behaviors, and struggles to form meaningful relationships with his peers. Overall, Allie's death adversely affects Holden's psychological health and he struggles to experience a happy, fulfilling life.