Why did Sohrab attempt suicide in The Kite Runner?

Amir hopes to be able to adopt Hassan's orphaned son Sohrab, but the process is more involved and difficult than he first thinks. There is a chance he might not be able to get his request granted. He is advised by an immigration lawyer to put Sohrab into an orphanage while he files an orphan petition, therefore making sure the boy is safe and cared for while Amir goes through the process; however, Sohrab is extremely dismayed by this idea. Earlier in the novel, Amir had promised that Sohrab would not be sent back to an orphanage and Sohrab is terrified of the idea of going to an orphanage to the point of sobbing uncontrollably. He has been sexually abused by adults in the past and does not want a repeat of that nightmarish scenario.

Despite his distress, there is little Sohrab can do in response since he is still only a child. During a night time bath, Sohrab slits his wrists and comes close to actually dying. At this point, he has given up hope that his life will ever get better and believes suicide is his only means of escaping pain. While his suicide attempt is unsuccessful, Sohrab is nevertheless drained of hope by this point in the narrative.