A group of senators Thursday called for an investigation of Fort Carson’s mental-health programs in a letter that alleges soldiers with PTSD have faced discrimination and have been unfairly discharged.

At issue is whether wardriven mental illness such as post-traumatic stress disorder in some soldiers led to misconduct that got them kicked out of the service, said Steve Robinson, an advocate with Veterans for America who has lobbied for months for an investigation.

Robinson is particularly irked that Fort Carson has publicly told its officers that mental illness does not excuse bad behavior.

“When you teach a class that says PTSD is not an excuse for drinking and drugs, then you are reinforcing bad information,” said Robinson, who contends that soldiers use drugs and alcohol to treat their own symptoms.

Eight Democrats, including presidential hopeful Barack Obama of Illinois, signed the letter along with one Republican, Sen. Kit Bond of Missouri. It asks for the Government Accountability Office, Congress’ research arm, to report on mental-health care throughout the Defense Department and on specific allegations at Fort Carson, including whether soldiers have been improperly discharged or have been discouraged from seeking care.

The letter says Obama and others want GAO to investigate because they haven’t received an adequate response from the Defense Department on mental-health questions.

The Department of Defense has an investigation of mentalhealth treatment at Fort Carson and other installations, but that report is not expected to be released until mid-May.

Alex Glass, a spokeswoman for Sen. Patty Murray, D-Wash., said the GAO letter reflects national concerns and is not aimed only at Fort Carson officials. She said Murray has been hearing about problems with mental-health care at Fort Lewis, near Tacoma, Wash.

Mental health has been a major health issue for Fort Carson soldiers returning from war. Nearly 600 Fort Carson soldiers were diagnosed with PTSD last year, up from 102 cases in 2003, when soldiers started returning from their first tours in Iraq and Afghanistan.

Fort Carson spokesman Lt. Col. David Johnson said commanders at the post welcome scrutiny.

After allegations were raised last year, commanders at the post admitted mishandling a handful of cases and implemented a training program for officers and sergeants on how to care for soldiers with mental-health issues.