What was wrong with Pony boy what is he sick with?

In "The Outsiders" by S.E. Hinton, Ponyboy Curtis is physically and emotionally affected by the traumatic events he experiences, particularly the deaths of his friends and the ongoing conflict between the Greasers and the Socs. He suffers from exhaustion and emotional distress, which manifests as a sort of mental breakdown after the violent incidents. While he doesn't have a specific illness, his struggles highlight the impact of violence and loss on his mental health.