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 with 242 in 2009, senior Army officials said.

The overall increase comes despite a massive effort by the Army's senior leaders to hire hundreds of mental health and substance-abuse counselors, along with a major push to reduce the stigma among soldiers of seeking mental health care. Most of those efforts have been focused on the active-duty force, which saw 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 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 they are deployed in combat, senior Army officials said.

The officials said they were puzzled by the significant increase in suicides in National Guard and Reserve units; that figure 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 a broader national trend driven by high levels of unemployment 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.

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

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 a third of National Guard combat veterans didn't have jobs when they returned home.

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

It is particularly hard 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 do active-duty soldiers, 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.

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.