Going to the movies was the worst: the crowds, the dark, the whispering.

“I would constantly be scanning for who was going to come stab me from behind,” says Robert Soliz, a 31-year-old former Army Specialist from San Joaquin, California. He was discharged in 2005 after serving in a heavy artillery quick-reaction force in South Baghdad. But fear, anxiety, depression and substance abuse swept into his life, and Soliz became one of 300,000 U.S. veterans of the wars in Iraq and Afghanistan with a diagnosis of post-traumatic stress disorder.

Isolated, his family deteriorating—“I couldn’t show affection, couldn’t hug my kids”—Soliz turned to the Palo Alto V.A. Medical Center. One recent morning, he talked about his progress. Hanging from his belt was a container of doggie treats, a link to the treatment he credits with saving his life. Soliz participates in Paws for Purple Hearts, one of four experimental programs nationwide that pair veterans afflicted by PTSD with Labrador and golden retrievers. Launched in 2008 by a social worker named Rick Yount, the program arranges for a veteran to spend six weeks with a dog, training it to be a mobility-assistance animal for a physically disabled veteran.

It’s no surprise that a doe-eyed creature like the one at Soliz’s feet can soothe, but other benefits are less predictable. The animals draw out even the most isolated personality, and having to praise the animals helps traumatized veterans overcome emotional numbness. Teaching the dogs service commands develops a patient’s ability to communicate, to be assertive but not aggressive, a distinction some struggle with. The dogs can also assuage the hypervigilance common in vets with PTSD. Some participants report they finally got some sleep knowing that a naturally alert soul was standing watch.