Though any animal can make a contribution to its owner’s physical and mental health, service dogs usually are trained to help with specific tasks like guiding and balance. For some of them, however, improving their owners’ mental health is the service they provide.

Since the 1990s, dogs have been trained to help people with Post-Traumatic Stress Disorder. They wake their owners out of nightmares, nudge them if they start to drive too fast, look out for them in crowded rooms, or warn them if someone behind them gets too close. Dogs’ sensitivity to the moods of humans – something that’s been bred into them for hundreds of years – equips them for these jobs. According to the AW2 (Army Wounded Warrior) blog, dogs have even been known to sense seizures, nightmares or flashbacks in their owners before they started.

On a more everyday level, dogs give simple companionship and a calming presence. They also can get their owners up, out of the house, and following a daily routine.

The U.S. military has taken up this idea and now is training dogs for the job and assigning them to combat veterans with PTSD. It’s a careful process that involves matching the dog to the person. Some veterans, instead of getting their own dogs, spend time with ones that are brought to them by their handlers.

In a twist on this story, one Marine veteran brought home a dog he’d found as a stray puppy in Iraq – and was told by a vet that the dog had PTSD. This brought him to question his own behavior with the dog and to realize that they both needed help.

It seems even when they’re suffering themselves, dogs can point the way for humans.