The Army will conduct a "thorough, multidisciplinary review" in response to a call from a group of 12 senators to investigate reports that the service discharged for misconduct as many as 22,000 soldiers who had been diagnosed with mental health problems.

"We strive to have a process that is fair, objective and deliberate, and that ensures due process and the maintenance of good order and discipline within the ranks," Acting Army Secretary Eric K. Fanning wrote in a letter to Sen. Chris Murphy, D-Conn. "The decision to separate a soldier from the Army for any reason is not an easy one, which is why we require a thorough review of the facts in each and every case. Nevertheless, I appreciate the concerns you raised in your letter and take them very seriously."

To address those concerns, Fanning directed the assistant secretary of the Army for manpower and reserve affairs to "conduct a thorough, multidisciplinary review of the issues you raised," Fanning wrote in the Nov. 30 letter.

The team tasked with the review will include the Army's inspector general and auditor general, Fanning wrote.

The letter was released by Murphy's office.

National Public Radio in October reported that the Army, since 2009, has separated 22,000 soldiers for misconduct after they returned from Iraq or Afghanistan and had been diagnosed with mental health problems such as post-traumatic stress and traumatic brain injury.

Murphy and 11 fellow senators called on the military to investigate the allegations in a Nov. 4 letter to senior Army leaders.

"We are troubled by recent allegations that the U.S. Army is forcefully separating for misconduct service members diagnosed with PTSD or TBI," they wrote. "We are concerned that it may be easier to discharge service members for minor misconduct — possibly related to mental health issues — than to evaluate them for conditions that may warrant a medical discharge."

As a result, they said, many of these soldiers will not receive "crucial" retirement, health care and other benefits. These actions also may discourage other service members from seeking the medical help they need, the lawmakers said.

Murphy on Thursday released a statement saying he was "especially troubled" to learn of reports of the soldier separations, and he applauded the Army's decision to conduct a review.

"I'm relieved that the U.S. Army is conducting a thorough investigation into what may have gone wrong and remain optimistic that they will fix their mistakes," he wrote.

In addition to the newly-directed review, the Army has in place a process to review discharges of soldiers who were separated for misconduct but who also were diagnosed with PTSD or TBI, Fanning wrote in his letter.

According to federal law, the Army Discharge Review Board expedites the review of applicants who request a change in the characterization of their discharge due to a diagnosis of PTSD or TBI, he wrote. In these cases, a physician participates as a board member, as required by the law, Fanning wrote.

The Army also has, over the last five years, put in place several steps to review and improve its behavioral health programs and administrative procedures, he said.

They include:

• Establishing a task force to conduct an extensive review of the Integrated Disability Evaluation System and implementing more than 45 recommendations to improve the system.

• Establishing an immediate appeal process where a soldier in the administrative separation process who does not agree with his or her diagnosis can receive, upon request, a second opinion.

• Establishing 58 new behavioral health clinics embedded at the brigade level. These clinics have resulted in an increase in consultations, from 900,000 in 2007 to more than two2 million in 2014.

• Publishing extensive policies to guide the diagnosis and treatment of soldiers with PTSD and establishing numerous avenues for care, including 11 intensive outpatient programs at Army installations with the highest number of deploying combat units.

"Know that the entire senior Army leadership, our commanders in the field, and every Army leader are committed to ensuring soldiers get the care they need," Fanning wrote. "We are working diligently to provide soldiers the best medical treatment available while on active duty, and to transition them seamlessly to the Department of Veterans Affairs for treatment as they re-enter civilian life."