WASHINGTON — National Guard and Reserve troops who have fought in Iraq and Afghanistan make up more than half of veterans who committed suicide after returning home from those wars, according to new government data obtained by The Associated Press.

A Department of Veterans Affairs analysis of ongoing research of deaths among veterans of both wars, obtained exclusively by The AP, found that Guard or Reserve members were 53 percent of the veteran suicides from 2001, when the war in Afghanistan began, through the end of 2005.

The research, conducted by the agency's Office of Environmental Epidemiology, provides the first demographic look at suicides among Iraq and Afghanistan veterans who left the military — a situation that veterans and mental health advocates worry might worsen as the wars drag on.

Military leaders have leaned heavily on Guard and Reserve troops in the wars. At certain times in 2005, members of the Guard and Reserve made up nearly half the troops fighting in Iraq.

Overall, they were nearly 28 percent of all U.S. military forces deployed to Iraq or Afghanistan or in support of the operations, according to data from the Defense Department through the end of 2007.

Many Guard members and Reservists have done multiple tours that kept them away from home for 18 months. When they returned home, some who live far away from a military installation or VA facility have encountered difficulty getting access to mental health counseling or treatment, activists have said.

Paul Rieckhoff, executive director of Iraq and Afghanistan Veterans of America, said the study's findings reinforce the argument that Guard and Reserve troops need more help as they transition back into the civilian world. The military's effort to re-screen Guard and Reservists for mental and physical problems three months after they return home is a positive step, Rieckhoff said, but a more long-term comprehensive approach is needed to help these troops — particularly in their first six months home.

"National Guardsman and Reservists are literally in Baghdad in one week and in Brooklyn the next, and that transition is incredibly tough," Rieckhoff said.

The VA has said there does not appear to be an epidemic of suicide among returning veterans, and that suicide among the Iraq and Afghanistan veterans is comparable to the same demographic group in the general population. However, an escalating suicide rate in the Army, as well as high-profile suicides such as the death of Joshua Omvig, an Iowa Reservist who shot himself in front of his mother in December 2005 after an 11-month tour in Iraq, have alarmed some members of Congress and mental health advocates.

In November, President Bush signed the Joshua Omvig suicide prevention bill, which directed the VA to improve its mental health training for staff and do a better job of screening and treating veterans.

According to the VA's research, 144 veterans committed suicide from the start of the war in Afghanistan on Oct. 7, 2001, through the end of 2005. Of those, 35 veterans, or 24 percent, served in the Reserves and 41, or 29 percent, had served in the National Guard. Sixty-eight — or 47 percent — had been in the regular military.

Statistics from 2006 and 2007 were not yet available, the VA said, because the study was based in part on data from the National Death Index, which is still being compiled.

Among the total population of Iraq and Afghanistan veterans who have been discharged from the military, nearly half are formerly regular military and a little more than half were in the Guard and Reserves, according to the VA.

Among those studied, more than half of the veterans who committed suicide were aged 20 to 29. Nearly three-quarters used a firearm to take their lives. Nearly 82 percent were white.

About one in five was seen at least once at a VA facility.

Last year, the VA started a suicide hotline. The VA and the military have also made other improvements in suicide prevention care, such as hiring more counselors and increasing mental health screening.

"The challenge is getting people to come to us before they commit suicide, knowing they can come and get help and knowing they have access to those resources," said Alison Aikele, a VA spokeswoman.

The VA study does not include those who committed suicide in the war zones or those who remained in the military after returning home from war.

Last year, the Army said its suicide rate in 2006 rose to 17.3 per 100,000 troops, the highest level in 26 years of record-keeping. The Army said recently that as many as 121 soldiers committed suicide last year. If all are confirmed, the number would be more than double the number reported in 2001.

Some mental health advocates have complained that there is no comprehensive tracking in one place of suicide among those who served in the wars, whether they be still in the military or discharged.

In October, the AP reported that preliminary research from the VA had found that from the start of the war in Afghanistan on Oct. 7, 2001, and the end of 2005, 283 troops who served in the wars who had been discharged from the military had committed suicide.

The VA later said the number was reduced to 144 because some of the veterans counted were actually in the active military and not discharged when they committed suicide.