Yet not everyone is convinced "the VA has the right stuff" to conduct the necessary experiments, said Corey Hudson, CEO of Canine Companions for Independence and president of the North American chapter of the umbrella organization, Assistance Dogs International.

Hudson said he hopes the study will be large enough to consider the broad gamut of symptoms associated with PTSD, as well as the anecdotal evidence suggesting canine companions can help tug the disorder's sufferers from their shells.

"There's something mystical and magical about dogs and people and placing them together," said Hudson, who has "worked with and against the VA" during his 22 years of experience with assistance dogs. Canine Companions for Independence has more than 900 puppy raisers and works to pair veterans with dogs regardless of whether the VA shells out for it.

Hudson doesn't cite scientific studies, such as the one that says canine interaction increases a human's level of oxytocin, a hormone that reduces anxiety and blood pressure.

Instead, he speaks about how dogs love unconditionally and don't judge. He explains how they naturally spark social interaction -- "Cool dog; can I pet her?" -- and how ownership precludes people from locking themselves in their homes, away from society.

"You can also use them as an excuse to get out of things or leave early," Hudson said.

Case in point

Shadow is one pooch accustomed to being used for such occasions.

The 2-year-old Labrador-Bernese mountain dog mix is the inseparable pal of Jennifer Haeffner, a seven-year Army veteran who had been housebound for about five years before meeting Shadow in the summer.

"He's a very active dog. It makes me do things. I don't have the option of hiding in the house. I have to go out," said the 41-year-old Ripon, California, resident.

During Operation Desert Storm, where she served for about nine months between 1991 and 1992, she was sexually assaulted on multiple occasions by other service members, she said. It's a fairly common occurrence that befalls about one in four women in the military, according to the VA.

It left her feeling alone in the world. She wanted to disappear. She forgot how to deal with people and eventually became a recluse, considering it a "good month" if she got out just once to shop for groceries.

She didn't attend any of her large family's gatherings. Too many people and too much noise, she said. It terrified her.

"For years after that, I would go out and wander the streets late at night, just hoping someone would kill me because I wasn't brave enough to kill myself," she said.

About five months ago, her therapist recommended that she meet Cortani.

Cortani recalls Haeffner wouldn't look her in the eye when they met. Her leg bounced when she spoke, and she pressed her fingernails into her arm. Her boyfriend was constantly by her side.

"You could just tell the pain and the anguish that even meeting me for the first time was causing," said Cortani, an Army veteran herself.

Operation Freedom Paws teaches participants to train their own dogs, to customize their behavior. First, the dogs learn to sit, then heel -- the basic stuff.

Shadow now knows how to pick things up for Haeffner so she doesn't put stress on her bad back and hips. He acts as a barrier, physically putting himself between her and any new people she meets.

When she wakes up feeling gloomy, he lets her stay in bed and pet him until she's ready to face the day. If she hears a sound during the night, he stays by her side as she checks it out, and Shadow is quick to snap her out of nightmares.