Yet even as his mental condition appeared to be deteriorating, Ivins maintained a government security clearance that gave him access to some of the world's most deadly pathogens.
The documents, which include excerpts of Ivins' e-mails to a friend, immediately raised questions about the scientist's top-level security clearance. At Fort Detrick, he was granted access to the Army's highly dangerous biodefense lab, where he performed research on anthrax and other dangerous substances.
Ivins kept his clearance until November, months after federal authorities acknowledge that they began closing in on him as a suspect in the anthrax investigation.
Army officials did not immediately explain how Ivins maintained his security clearance.
Mark Zaid, a Washington lawyer who specializes in national security issues, said Ivins' behavior, as described in the documents released yesterday, should have "raised many red flags."
"One would think that employees within a weapons laboratory would pay careful attention to the behavioral signs of their co-workers and appropriately report those concerns," Zaid said. "No one wants to report on a colleague and friend, but we're dealing with life-and-death situations. Scrutiny should be stricter."
He said the Army should conduct an internal investigation into the matter.
In the unsealed documents, federal investigators describe Ivins as dealing with significant mental health issues and stress in 2000 and 2001. He sought help from a psychiatrist and was immediately prescribed medication starting in February 2000, the documents show.
The papers contain excerpts from e-mails in which Ivins writes to a friend about feeling isolated and depressed.
"What is REALLY scary is the paranoia," he wrote at one point.
On Sept. 26, 2001, he wrote, "I'm really the only scary one in the group. Others are talking about how sad they are or scared they are, but my reaction to the WTC/Pentagon events is far different. Of course, I don't talk about how I really feel with them - it would just make them worse. Seeing how differently I reacted than they did to the recent events makes me really think about myself a lot."
It was not clear whether Army officials were made aware of the mental health issues.
Zaid said Ivins' top-secret clearance would likely have been reviewed every three years. The clearance includes a mental health check, he said, though having sought mental health treatment would not disqualify a person from getting the clearance.
Mark F. Riley, a retired Army intelligence officer who is now a lawyer focusing on security-clearance issues, said it is not unusual for the Army to review a person's clearance because of odd behavior. Sometimes, the Army will suspend a clearance until the employee undergoes a psychological evaluation, he said.
According to Defense Department regulations, anyone who handles biological select agents and toxins shall be "emotionally and mentally stable, trustworthy and adequately trained. ... "
Caree Vander Linden, a spokeswoman for the U.S. Army Medical Research Institute of Infectious Diseases, or USAMRIID, while not addressing Ivins' mental state, said employees undergo mental health checks at Fort Detrick. She pointed out that Ivins played a key role in anthrax vaccine research and development until last year.
Jeffrey Taylor, the U.S. attorney for the District of Columbia, said yesterday that Ivins was able to maintain a seemingly normal professional and personal life, not arousing suspicion among those around him: "He has been this way for a number of years and was still able to carry on his professional life at USAMRIID."
Sun reporters Stephen Kiehl and David Wood contributed to this article.