An Army memo says Sgt. Bowe Bergdahl showed signs of mental illness when he walked off his post in Afghanistan in 2009.
The memo was one of a number of new documents released by Bergdahl's defense attorneys Thursday.
It details the findings of a Sanity Board Evaluation that Bergdahl had a "severe mental disease or defect" when he walked off his post and was clinically diagnosed with schizotypal personality disorder.
Bergdahl is facing a court-martial for charges of desertion and misbehavior in front of the enemy for leaving his post in Afghanistan.
He was subsequently captured by the Taliban and held prisoner for five years. He was released in 2014 as part of a prisoner swap by the Obama administration for five senior Taliban commanders held at Guantanamo.
In interviews aired on NPR's "Serial" podcast, Bergdahl said he left his post because he hoped to trigger an alert and gain the attention of senior military leaders. He wanted to alert them to what he believed were dangerous actions by his commanders.
Bergdahl said he believed his commander hated his unit and could purposely send it out on suicide missions.
The board also said, however, that "though SGT Bergdahl did have a severe mental disease or defect at the time of the alleged criminal conduct, he was able to appreciate the nature and quality and wrongfulness of his conduct."
It also said that Bergdahl was not "presently suffering from a mental disease or defect rendering him unable to understand the nature of the proceedings against him or to conduct or cooperate intelligently in the defense."
The documents appeared on a website created by Bergdahl's defense attorneys.
Bergdahl is being prosecuted by a military court, and there is no federal repository for court documents.