We've got more evidence that legalized marijuana is not unleashing out-of-control drug use.

This time it comes from the military. A study by the Army found that fewer soldiers are testing positive for marijuana in Colorado and Washington, the two states that have legalized the drug. That means that soldiers serving in those states have not broken their commitment to remain drug-free simply because pot is legal where they live. Prior to legalization, military leaders argued that soldiers stationed in states with legalized recreational marijuana would begin using the drug at higher rates, according to military.com. Instead, there has been about a half percentage drop.

When marijuana became legal in those states, military brass made all efforts to keep pot out of military facilities:

While civilians took up the newly legal vice in Washington and Colorado, the Defense Department has redoubled efforts to get pot out of the ranks. Signs at the gates of military bases in the Pikes Peak region [in Colorado] emphasize that marijuana possession remains a federal crime and soldiers caught smoking grass face harsh punishment under the Uniform Code of Military Justice. 

The results of military drug tests in Washington and Colorado echo recent research that says more accessible marijuana does not lead to rampant use of the drug. According to Gallup, marijuana use among 18-29 year olds has fallen 20% since 1985.

The military's relationship with drugs

Drugs have been a sore subject for the military since the Vietnam War when marijuana use was common among American soldiers. The image of soldiers smoking pot amidst Vietnamese rice paddies became a fixture of pop culture's portrayal of the war. Much more dangerous, after 1970, 1 in 5 enlisted troops were addicted to heroin at some point during their time in Vietnam. Today, the military has a zero tolerance policy toward illicit drug use that includes less dangerous drugs like marijuana. This has likely contributed to the decline in positive tests since this tough policy was installed two decades ago.

"It would be a huge mistake for us to change our standards and to allow for [drug use] to be part of soldiering again," Army Gen. Chuck Jacoby told military.com. Jacoby is the top-ranking military leader in the Pikes Peak region in Washington state.

Should the military be using pot?

Some believe, though, that marijuana may be effective in reducing the effects of post-traumatic stress disorder (PTSD), which is a serious condition affecting thousands of soldiers who served in Afghanistan and Iraq. According to the Veterans Affairs Department, between 11 percent and 20 percent of Iraq and Afghanistan veterans suffer from PTSD. The disorder can lead to depression, anxiety, strained relations with family and friends, and there is evidence that PTSD correlates with suicide. Psychiatrist Sue Sisley has received a $2 million grant from the Colorado Board of Health to research marijuana's effect on 80 veterans with PTSD. She became interested in the drug's potential when some of her PTSD patients reported improvement after self-treating with marijuana. 

"I've met expert growers who are absolutely growing some of the most stunning marijuana with some gorgeous flowering plant material that would probably really benefit these veterans," Sisley told the Boulder Daily Camera.

A study published last November found that the administering of synthetic cannabinoids to rats after a traumatic event prevents symptoms of PTSD.