Thirty-one Marines committed suicide in 2004, all of them enlisted men, not commissioned officers. The majority were younger than 25 and took their lives with gunshot wounds, according to Marine statistics. Another 83 Marines attempted suicide. There were 24 suicides in 2003, and there have not been more than 29 in any year in the last 10.

Although last year's suicide rate rose, it was still below the national average for a comparable civilian group, in keeping with an established pattern of suicide being lower in the U.S. military than in the civilian population.

Marine commanders say the rise in suicides continues a worrisome three-year trend that is likely linked to stress from the sharply increased pace of war-zone rotations. At the same time, they said the increase in suicides is not directly related to service in Iraq or Afghanistan; since 2001 24 percent of the suicides have been committed by Marines who have been deployed there, the statistics show.

It is "not only Iraq, it's just the ops tempo [operational tempo] in general, that's what I think," Gen. Michael W. Hagee, the Marine Corps commandant, told reporters at a breakfast meeting yesterday.

Hagee's remarks echoed a strong warning in a Dec. 13 memo that he issued on suicide prevention. "This problem is pervasive and is impacting Marines throughout the Corps, not just those who have been deployed in support of the global war on terrorism," the memo said. "The increased operational tempo that our Corps is experiencing may be affecting the ability of our Marines to deal with perceived overwhelming stresses associated with relationship, financial, and disciplinary problems."

Indeed, about 70 percent of Marine suicides over the past four years have been caused by problems in personal relationships, which can be exacerbated by heavy workloads, said Cmdr. Thomas Gaskin, a behavioral health specialist for the Corps' Personal and Family Readiness Division at Quantico. "That is the single biggest stressor," he said.

With a force that is the youngest in the military services and predominantly male, the Marine Corps has generally experienced the highest suicide rate among the military branches because its demographics mirror a high-risk group in the general population. More than 60 percent of Marines are younger than 25, and 16 percent are teenagers.

Suicide rates for all the services began rising in 2002, and the Army had an increase in 2003, the first year of the Iraq war. This leads experts to believe that stress is broadly linked to deployments.

However, despite ongoing rotations to Iraq, the Army's suicides in that country fell back closer to historic levels last year, officials said. That may suggest that, as with the Marine Corps, suicide rates may be more connected to the general demands on the force than to service in combat zones, officials said.

Marine officials said the suicides in their force show no definitive causal patterns. "There are no clear trends among any specific groups," said Greg Gordon, a spokesman for the Personal and Family Readiness Division.

Hagee warned that while some Marines have displayed obvious warning signs of suicidal tendencies -- such as a preoccupation with dying, risky behavior, withdrawal or giving away their possessions -- many do not. In his memo, he warned that some Marines feel stigmatized for seeking help.

"They may feel it is not acceptable to ask for help because they don't want to be labeled as 'weak' or 'defective' in the eyes of their subordinates, peers, or leaders," he wrote. Commanders, he emphasized, must redouble their efforts to make Marines feel comfortable in revealing problems that could lead to suicide.

Growing concerns over suicide have led both the Army and Marines to dispatch more mental health professionals to Iraq and Afghanistan, in an effort to provide more immediate prevention. In response to the rising number of suicides in Iraq in 2003, the Army deployed several "combat stress" detachments there to allow psychologists to treat soldiers who demonstrate suicidal tendencies without requiring them to leave the country.

Similarly, the Marines in 2004 launched an "operational stress control and readiness program" in which mental health professionals are embedded in Marine divisions in Iraq and travel to individual units to treat Marines. "Before, we had to ship them out of theater. Now they can provide help immediately," Gordon said.

The Marines are also developing a prevention tool for commanders called "a leader's guide for managing Marines under stress," which is expected to be issued early this year and includes checklists of what to do for suicidal behavior.