SCHOFIELD BARRACKS — The Army's top uniformed officer said even though the rest time between deployments is increasing for soldiers, an increasing suicide rate remains a mystery and concern.

The Army reported 24 potential suicides for January (some are still being investigated), outnumbering the 16 U.S. combat deaths in Iraq and Afghanistan for the month.

There were at least 128 Army suicides last year.

"The fact of the matter is, we just don't know" why suicides have increased, Army Chief of Staff Gen. George W. Casey Jr. said Friday. "It's been very frustrating to me with the effort that we made over the last year, and we did not stem the tide."

The Army and the National Institute of Mental Health in late 2008 began a five-year, $50 million study to examine the problem. The study includes the National Guard and Army Reserve.

Casey is in Hawai'i for the funeral of Gen. Frederick Weyand, a key figure in the Vietnam War and former Army chief of staff who died Feb. 10 at age 93 at the Kāhala Nui retirement home.

An important component in mental health is longer "dwell," or at-home time between deployments, and efforts are being made to increase that time, officials said.

"For the last five years, we've been deploying at a rate of about one year out, one year back," Casey said.

More and more, units are getting 17 to 18 months at home, and with the addition of 30,000 soldiers to the Army's ranks and a drawdown in Iraq, Casey said he expects two years between deployments by this time next year.

The four-star general and former commander of multinational forc- es in Iraq said a study showed it takes two to three years to fully recover from a one-year combat deployment, "and when you don't have enough time to completely recover, what you see is the effects start to build up, so they become cumulative."

Enrollments for drug and alcohol treatment have increased, and the divorce rate has increased slightly overall, with a greater jump for female soldiers, Casey said.

About a third of soldier suicides occur on deployment, a third occur after a deployment, and a third involve soldiers who haven't deployed, he said.

The Army is "working very hard" on a program called Comprehensive Soldier Fitness, which started in October and focuses on mental, emotional and social well-being to teach soldiers to be more resilient, Casey said.

"I just can't help but think the additional stresses brought on by these deployments exacerbate existing conditions," Casey said. "So what we're trying to do is give every soldier and family member and civilian the skills that they need to deal with life's challenges."

Casey reiterated his concern that the possible repeal of the "don't ask, don't tell" policy could affect readiness and military effectiveness.

The 1993 policy bars openly gay individuals from serving in the U.S. military, but prevents the military from asking a service member's sexual orientation.

Defense Secretary Robert Gates, who expressed support of a repeal, recently launched a review of the policy. The study is expected to take about a year.

"I've gone out over the past several months and talked to different segments of the Army, different groups, and gotten their input," Casey said. "And there's apprehension and there's uncertainty, and that's why I think it's so important that we study this."