WASHINGTON — More than half of all veterans who took their own lives after returning from Iraq or Afghanistan were members of the National Guard or Reserves, according to new government data that prompted activists yesterday to call for a closer examination of the problem.

A Department of Veterans Affairs analysis of ongoing research of deaths among veterans of both wars — obtained by the Associated Press — found that Guard or Reserve members accounted for 53% of the veteran suicides from 2001, when the war in Afghanistan began, through the end of 2005.

The research, conducted by the department’s Office of Environmental Epidemiology, provides the first demographic look at suicides among veterans from those wars who left the military.

A public affairs director for the Veterans of Foreign Wars, Joe Davis, said the Pentagon and VA must combine efforts to track suicides among those who have served in those countries in order to get a clearer picture of the problem.

“To fix a problem, you have to define it first,” Mr. Davis said.

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% of all American military forces deployed to Iraq or Afghanistan or in support of the operations, according to Defense Department data through the end of 2007.

Many Guard members and Reservists have done multiple tours that kept them away from home for 18 months, and that is taking a toll, Senator Murray, a Democrat of Washington, said in a statement yesterday.

“Until this administration understands that repeated and prolonged deployments are stretching our brave men and women to the brink, we will continue to see these tragic figures,” Mr. Murray said.

Executive director of Iraq and Afghanistan Veterans of America, Paul Rieckhoff, said 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, but a more long-term, comprehensive approach is needed to help them. “National Guardsman and Reservists are literally in Baghdad in one week and in Brooklyn the next, and that transition is incredibly tough,” Mr. Rieckhoff said.

The VA has said there does not appear to be an epidemic of suicide among returning veterans, and that suicide among the newer 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 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 October 7, 2001, through the end of 2005. Of those, 35 veterans, or 24%, served in the Reserves and 41, or 29%, had served in the National Guard. Sixty-eight — or 47% — 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% were white. About one in five was seen at least once at a VA facility. Last year, the VA started a suicide hot line. 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,” a VA spokeswoman, Alison Aikele, said.

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 a 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.