Every month, a new cycle of training begins with yet another class of veterans in a program run by the northern Florida K9s for Warriors. The seven-year-old nonprofit is one of dozens of private organizations that offer psychiatric service dogs to address the military's mental health crisis. The numbers are startling on veteran suicides, and this is working, said Rory Diamond, a former federal prosecutor who quit to become chief executive of K9s for Warriors. A recent [Purdue University] study ... used standard questionnaires to assess PTSD symptoms and other aspects of mental health among 141 K9s for Warriors applicants, half teamed with a service dog and half on a wait list. Those with dogs showed significantly lower levels of post-traumatic stress, depression and social isolation, with higher levels of psychological well-being. Dogs have provided services to humans for millennia, often as hunting and herding partners. But not until World War I were they systematically trained to assist people with disabilities, as guides for the blind. Service dogs now prompt deaf people when a doorbell rings, retrieve pills for people in wheelchairs and alert people with diabetes to blood sugar spikes. Psychiatric service dogs [blend the missions of] of task-oriented service canines and animals seen as providing emotional support. While the dogs paired with veterans with PTSD are commonly trained to wake them from nightmares ... advocates also laud their ability to soothe a panicking vet and provide companionship.