Matt Kahl made it home after two tours in Afghanistan, but was wracked with pain from physical injuries, and on a host of anti-anxiety medication to try and treat his mental anguish.

"About ten months after I got back, I attempted suicide," Kahl told CBS News' Barry Petersen.

"I was completely hopeless," recalled the veteran, who said he was on about 15 different medications.

Until the day he tried marijuana.

"Suddenly, my extremely overactive, hyper-vigilant mind started to calm down," he told Petersen, "and my pain gradually started to go away, too. I needed less of these other medications, and shortly afterwards, I determined that I absolutely have to move to a state that allows this so that I can get my life back."

He moved his family to Colorado and now works with a group called Grow4Vets. He and other volunteers recently spent a day putting together bags of marijuana products that are given away on holidays, like Memorial Day.

The marijuana is meant to treat war wounds -- both the mental and the physical kind that doctors often treat with drugs like oxycontin. According to the VA, 20 percent of veterans returning from Afghanistan and Iraq suffer from post-traumatic stress. Current treatments range from therapy to prescription drugs, but the group wants to replace pills with pot, according to veteran and Grow4Vets founder Roger Martin.

"Anybody that's been on narcotic medication especially wants to get off of it," he said. "I really have not met anybody who just enjoys being in a drug stupor."

But because marijuana is still considered a Schedule 1 drug at the federal level, there has been very little research into the effects of pot and post-traumatic stress disorder. The House recently voted down a bill that would allow VA doctors to speak with patients about medicinal marijuana, even in states like Colorado where it's legal.

Soldiers and pot have been together since the Vietnam War, as pot shop owner Toni Fox knows well. Her father came home from Vietnam suffering from post-traumatic stress disorder. Marijuana helped but it was illegal, so not always available.

"He struggled his whole life," she said. "When I was 14 he ended up committing suicide, and it was directly related to the post-traumatic stress disorder from Vietnam."

Which is why she gives Grow4Vets marijuana from her crop area, and money from the shop's tip jar.

"I believe in my heart of hearts that, if he would have had access to cannabis, he would be alive today," said Fox.

Critics are still dubious, given the fact there is little to no scientific proof that pot actually helps with post-traumatic stress disorder.

"Why the hell not? Why don't we study it? Why don't we run these clinical trials?" said Kahl. "I'm absolutely convinced that it works."

For Matt and wife Aimeé, the relief he gets from marijuana means a second chance at healing from Afghanistan, and that's nothing less than a second chance at life.