WASHINGTON — The Pentagon's top uniformed officer is calling for all returning combat troops, from privates to generals, to undergo screening for post-traumatic stress with a mental health professional, a move aimed at stemming an epidemic of psychological issues among veterans.

Adm. Michael Mullen, chairman of the Joint Chiefs of Staff, said there's a reluctance to acknowledge psychological problems for fear of showing weakness. Troops now fill out questionnaires after combat tours that help determine if they have suffered psychological damage. They're examined by medical professionals for physical injuries, but not by mental health experts.

"I'm at a point where I believe we have to give a (mental health) screening to everybody to help remove the stigma of raising your hand," Mullen said. "Leaders must lead on this issue or it will affect us dramatically down the road."

About one in five combat veterans from Iraq and Afghanistan suffer from post-traumatic stress or depression, according to a study by the RAND Corp. In all, RAND estimates that 300,000 veterans have been affected and it could cost more than $6.2 billion to treat them.

Half of the troops RAND surveyed reported that they had a friend who was seriously wounded or killed. Rates of post-traumatic stress disorder (PTSD) and depression were highest among soldiers and Marines, the study said.

"The PTS issue is something we just all have to focus on," Mullen said. "I think it's a bigger problem than we know."

Mullen's proposal is in its infancy, and there are no estimates about its potential costs or when it would start. Another potential complication is the number of available mental health professionals, such as psychiatrists, psychologists and social workers. Pentagon budget records show the military has increased signing and retention bonuses for these professionals in recent years to make up for shortages.

Troops also know how to evade certain mental health questions to avoid treatment. Mullen said the Pentagon still has not addressed the negativity surrounding mental health care, which has kept many troops from seeking help.

A trained mental health professional who meets one-on-one with a service member can detect signs of post-traumatic stress in as few as five minutes.

Troops worry their careers will suffer if they seek mental health care, said Terri Tanielian, co-director of RAND's Center for Military Health Policy Research. If Mullen's plan increases access to confidential care, she said, "we will go a long way to removing the stigma associated with getting mental health care."