Suicides among soldiers serving on active duty decreased modestly in 2010 for the first time in six years, even as the Army National Guard and Reserve saw a major increase in the number of soldiers taking their own lives.

New figures released Wednesday by the Army show how difficult it has been for officials to drive down the number of suicides in a force that remains under serious strain. Last year, 301 active-duty, reserve and National Guard soldiers committed suicide, compared to 242 in 2009, senior Army officials said.

The overall increase comes despite a massive effort on the part of the Army's senior leaders to hire hundreds of mental health and substance abuse counselors and a major push to reduce the stigma among soldiers of seeking mental health care. Most of those efforts have been focused on the Army's active-duty force, which did see a small drop in the number of suicides, from 162 in 2009 to 156 last year.

Army officials credited the decline to improved outreach efforts and expressed hope that as troop numbers decrease in Iraq and the strain on the force lessens, the overall suicide rate will continue to fall.

"When we put more time between deployments, that will be a huge factor in helping with this problem," said Gen. Peter Chiarelli, the Army's vice chief of staff.

By the end of this year, most active-duty soldiers should be able to spend at least two years at home for every year that they are deployed in combat, senior Army officials said.

The officials said they were puzzled by the significant increase in the number of suicides in National Guard and Reserve units, which almost doubled from 80 deaths in 2009 to 145 deaths in 2010.

"If you think you know the one thing that causes people to commit suicide, please let us know, because we don't know what it is," Chiarelli said.

About half of the National Guard and Reserve soldiers who killed themselves last year had never deployed to a combat zone; by contrast, about two-thirds of the active-duty soldiers who killed themselves had previously deployed to Iraq or Afghanistan, or were there when they took their lives.

Senior Army officials speculated that the increase in Guard and Reserve suicides could be part of part of a broader national trend driven by elevated levels of joblessness and a bad economy. "We are the canary in the mine shaft on this issue," said Maj. Gen. Raymond W. Carpenter, the acting director of the Army National Guard.

Comparing the suicide rate among soldiers to the general population is difficult. The latest national suicide statistics, which are compiled by the Centers for Disease Control and Prevention, are now almost three years old.

Carpenter said that the strain of combat deployments likely played a role in the increase in suicides in the Guard.

It is particularly difficult for the military to reduce the suicide rate among reservists, who typically drill with their units only a couple of days each month. Reservists have far less contact with their commanders than members of the active-duty force, who often live on base.

"You may have a reservist who lives in Georgia but belongs to a unit in Tennessee,"said Lt. Gen. Jack Stultz, the Army's top Reserve officer.

Some Army officials also speculated that Guard and Reserve soldiers returning from combat were having a harder time finding jobs. In one Washington state unit, as many as one-third of returning National Guard combat veterans didn't have jobs when they returned home.

The Army also has focused less attention on reducing the suicide rate among reserve troops than it has on active-duty soldiers. "We know we have a problem that we didn't recognize before," Chiarelli said.