By Joan Shim

(LifeWire) -- Jo Hanna Schaffer's dog is more than a best friend. The 67-year-old Vietnam veteran, a former Army medic, suffers from post-traumatic stress disorder (PTSD), and three years ago, she decided to get a service dog, a Chihuahua named Cody. Cody barks if someone is approaching from behind and cuddles with her when she is depressed.

"I never took a pill for PTSD that did as much for me as Cody has done," says the Billerica, Massachusetts, resident, who no longer takes medication for the disorder.

Schaffer is one of a growing number of veterans with PTSD who are turning to an alternative therapy: psychiatric service dogs.

Like guide dogs for the blind, psychiatric service dogs aid people with mental illnesses, from anxiety disorder to bipolar disorder to PTSD. The dogs are trained to know when their owners are depressed or having a panic attack, for example, and the animals might calm them down by curling up in their lap or giving a nudge.

The use of service dogs for mental illness has emerged in the past decade, says Dr. Joan Esnayra, founder and president of the Psychiatric Service Dog Society. Esnayra coined the term "psychiatric service dog" in 1997 and has worked with thousands of people who are using the animals. She estimates that the society's online community is adding more than 400 members each year.

The cost of a dog can vary widely, Esnayra says, depending on whether the animal is being obtained through an professional organization or through a private trainer. Professional organizations like the St. Francis of Assisi Service Dog Foundation in Roanoke, Virginia, which have their own breeding programs, may spend upwards of $20,000 to produce a dog, but charge applicants only a few hundred dollars by offsetting the expense with corporate donations, she says.

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