David Lewis / AP file Sgt. Brandon Morgan, right, is embraced by his partner Dalan Wells, in a helicopter hangar at a Marine base in Kaneohe Bay, Hawaii, upon returning from a six-month deployment to Afghanistan in this photo taken in February 2012.

Updated at 5:40 p.m. ET: The repeal of the military’s “don’t ask, don’t tell” policy in 2011 has not had a negative impact on force readiness, recruitment or retention, contrary to predictions that it would, according to a new study published Monday.

The policy, implemented in 1993 while then President Bill Clinton was pushing for openness in the military, was repealed on Sept. 20 last year. Before its enactment and the repeal, service members had said having openly gay troops would harm the military.

But the study by the Palm Center, which conducts research on sexual minorities in the military, determined those concerns were unfounded. The research by nine scholars, some professors at military academies, began six months after the policy (known as DADT) ended and wrapped up near the one-year mark.

The scholars said they interviewed opponents and advocates of the repeal, as well as active duty service members who are gay, and conducted on-site field observations of four military units, among other research. They also reached out to 553 of the nearly 1,200 generals and admirals who signed a 2009 letter saying the repeal would undermine the military and eventually got interviews with 13 officers.

“Our conclusion, based on all of the evidence available to us, is that DADT repeal has had no overall negative impact on military readiness or its component dimensions, including cohesion, recruitment, retention, assaults, harassment or morale,” according to the study. “Although we identified a few downsides that followed from the policy change, we identified upsides as well, and in no case did negative consequences outweigh benefits. If anything, DADT repeal appears to have enhanced the military’s ability to pursue its mission.”

Their research also showed that the repeal hadn’t been responsible for any new wave of violence or physical abuse among service members and appears to have enabled some gay troops to resolve disputes around harassment in ways that were not possible before.

Related: Four Marines accused of beating man in possible gay hate crime

However, there were two “verifiable resignations” of military chaplains due to the repeal, which also triggered a drop in individual morale for some service members who were opposed to it, the study said.

Implementation of the repeal was "proceeding smoothly" across the Department of Defense, said a spokeswoman, Eileen M. Lainez.

"We attribute this success to our comprehensive pre-repeal training programs, continued close monitoring and enforcement of standards by our military leaders, and service members' adherence to core values that include discipline and respect," she said in an e-mail to NBC News. "Defense department leadership and the services remain engaged in implementation, and a formal monitoring process ensures continual assessment."

The Center for Military Readiness, an independent public policy group specializing in the military and social issues, has previously questioned success of the repeal.

“From the standpoint of a small minority of LGBT personnel, repeal certainly was a ‘success’ on September 21, the first day after repeal implementation,” the group said in a May 16 blog on its website. “It is too soon, however, to draw conclusions about the consequences of LGBT law (formerly DADT) and related policies for most people in the military. The poor economy will continue to mask potential recruiting and retention problems for years to come.”

The group did not immediately reply to a request for comment by NBC News on the Palm Center study.

Since the repeal, the Defense Department has held a gay pride event and allowed service members to march in pride parades in uniform, according to reports.

During a May 10 briefing, Defense Secretary Leon Panetta said the repeal was “going very well” and was not impacting morale, unit cohesion or readiness.

“And very frankly, my view is that the military has kind of moved beyond it,” he said. “It's become part and parcel of what they've accepted within the military.”

The Palm Center is part of the Williams Institute, an independent think tank conducting research on sexual orientation and gender identity law and public policy, at the University of California Los Angeles, School of Law.

More content from NBCNews.com:

Follow US News from NBCNews.com on Twitter and Facebook