Feeling under the weather? Need a pick-me-up? Give a furry friend a pat on the belly, and call me in the morning.

As far back as prehistoric times, humans kept domesticated animals for hunting, protection and other practical needs. Then around 400 years ago, people began to sense intrinsically what researchers today are proving empirically: that keeping animals for companionship is also good for the body and soul.

Studies show that owning a pet—dog, guinea pig, horse or any other animal a person connects with—can lower the owner’s blood pressure, reduce anxiety, improve social interactions, establish caring and empathetic behaviors, and even aid in recovery from illness and disease.

One landmark study revealed that patients with heart disease were less likely to die of the condition within a year if they owned a pet than if they did not. And a 2011 study published in the Journal of Personality and Social Psychology found that pet owners are happier, more physically fit, less lonely and more content with themselves than those who don’t own pets.

For healing purposes, the animal needn’t be a pet or even familiar to a patient, says Dr. Sandra Barker, director of the School of Medicine Center for Human-Animal Interaction at Virginia Commonwealth University. “I continue to be amazed by the very powerful therapeutic effect that a single unfamiliar therapy dog can have on a particular patient,” she says. “Some patients have responded to nothing else.”