Wayne Pacelle has a demanding job as president and chief executive of the Humane Society of the United States. This is one of the reasons he brings Lily, his beagle mix, to work with him. He is convinced that animals "are a necessary ingredient in our emotional well-being,'' he says. "I deal with many stressful issues, and I see terrible cruelty,'' he adds. "But when Lily puts her head on my lap, it calms me.''
Pacelle can't scientifically document the positive effects he gains from his connection with Lily (and Zoe, his cat.) But his experience supports what researchers who study human/animal interaction have concluded: Pets, especially dogs, seem to be good for our health.
"Dogs make people feel good,'' says Brian Hare, an associate professor of cognitive neuroscience at Duke University, who points out that dogs are found now in some courtrooms, exam study halls, hospitals, nursing homes, hospice-care settings, classrooms, airports and elsewhere, "and their only job is to help people in stressful situations feel better. Many people seem to respond to dogs in a positive way.''
Scientists believe that the major source of people's positive reactions to pets comes from oxytocin, a hormone whose many functions include stimulating social bonding, relaxation and trust, and easing stress.
Research has shown that when humans interact with dogs, oxytocin levels increase in both species. "When parents look at their baby and their baby stares into their eyes, even though the baby can't talk, parents get an oxytocin boost just by eye contact,'' Hare says. "Dogs have somehow hijacked this oxytocin bonding pathway, so that just by making eye contact, or [by] playing and hugging our dog, the oxytocin in both us and our dog goes up. This is why dogs are wonderful in any kind of stressful situation.''
Miho Nagasawa, a postdoctoral fellow at Jichi Medical University in Shimotsuke, Japan, has found that mutual gazing between humans and their dogs increases the owners' oxytocin levels. This helps decrease anxiety and arousal levels, and slow the heart rate. "The positive interaction between humans and dogs via mutual gazing may reduce stress activity for each other,'' she says.
About 43 million American households have dogs and about 36 million households have cats, according to the 2012 U.S. Pet Ownership & Demographics Sourcebook, a publication of the American Veterinary Medical Association.
History provides numerous stories - some of them probably apocryphal - of the therapeutic benefits of dogs, both physical and psychological. In ancient Egypt, for example, people believed that a dog's lick could heal sores or lesions (there may be a basis in fact for this, because dogs' saliva contains antibacterial and antiviral substances, as well as growth factors); in 19th-century mental institutions in England, pets were used to calmresidents; in 1880, former Civil War nurse Florence Nightingale wrote that a small pet "is often an excellent companion for the sick, for long chronic cases especially.''
In modern times, science has stepped in to provide a clearer link. A 1980 study found that more heart-attack victims with pets survived beyond the one-year mark than those without, a finding that was reproduced 15 years later.
Other studies have shown that pet ownership seems to decrease coronary-disease risk factors involving blood pressure, cholesterol and triglycerides, among other things.
A 2009 study, for example, looked at 4,435 people, more than half of them with cats, and found a significantly lower risk of heart-attack deaths for the cat owners.
Another study, which looked at 240 married couples, found lower heart rates and blood pressure among those with pets than among those without. The pet owners also experienced milder stress responses and a faster recovery from stress when they were with their pets rather than with a spouse or friend.
As for staying healthy in general, it's no surprise that having a dog can help you stay more active. One study involving more than 2,000 adults found that dog owners who regularly walked their dogs were more physically active and less likely to be obese than those who didn't own or walk a dog.
Another, which looked at more than 2,500 people ages 71 to 82, found that regular dog walkers tended to walk faster and for longer periods each week than those who did not have dogs to walk. They also showed greater mobility inside their homes.
Some research suggests that childhood exposure to dogs and cats can protect against developing allergies and asthma later in life, possibly because the contact with pet microbes occurs while the immune system is still developing.
Denise Harris of Columbia, Md., has had rheumatoid arthritis for 30 years; when she's feeling ill, she often naps with her Irish wolfhounds, Carrick and Fearghus. She says Fearghus mothers her when she's getting sick, sensing what's coming before she does and herding her to the bed or sofa. "Sure enough, a couple of hours later, I'm running a fever," she says. "He then literally watches over me till the fever breaks."
She calls Carrick her crutch. "When I fell in the blizzard last winter, he ran to my side, stood over me until I could sit up, let me use him to pull myself up, then supported me, letting me lean against him all the way into the house and to the sofa."
Of course the hounds are good for her health, she says. For one thing, she takes long walks with them. "And I can always count on Fearghus for a hug when I'm feeling down," she says.
Both the Centers for Disease Control and Prevention and the National Institutes of Health are interested in the potential health value of having pets: NIH first raised the human/pet connection nearly 30 years ago, recommending that scientists take pets into account when conducting health research, and the agency has funded a number of studies into the impact of pet ownership.
Lori Kogan, an associate professor of clinical sciences at the Colorado State University College of Veterinary Medicine and the editor of the Human-Animal Interaction Bulletin, says that pets can be especially helpful for people facing emotional difficulties. "Dogs have a positive impact on depression and anxiety,'' Kogan says. "When someone loses a spouse or partner, for example, having a dog provides a reason to get up and be social,'' she says. For many older people, "it's the only relationship they have.''
In one study, researchers concluded that women living alone were "significantly more lonely" than those who were living with pets, and noted that having a pet might "compensate for the absence of human companionship."
This may explain the value many people find in therapy dogs, which are trained to help people deal with worry, unhappiness and anxiety, and have been found to even reduce the perception of pain.
While dogs are most frequently used for therapy purposes, says Mary Margaret Callahan of Pet Partners, the group's registry of available therapy animals also includes cats, horses, rabbits, guinea pigs, llamas, potbellied pigs, birds and domesticated rats.
Therapy dogs are widely used to help veterans cope with post-traumatic stress disorder and have been used to help calm autistic children. In June, therapy dogs were brought in to relax swimmers competing in the U.S. Olympic trials in Omaha suffering from pre-race jitters.
Therapy golden retrievers from Lutheran Church Charities were sent to Orlando in June to comfort survivors as well as those who lost loved ones in the Pulse nightclub shooting that left dozens dead. A New York funeral home provides mourners with a dog that even "prays'' with them.
A recently released study found that therapy pets can help first-year university students suffering from homesickness and possibly help in lowering college dropout rates.
Of course, there are times when the emotional interaction with pets can be difficult. When they misbehave or are sick (or worse), we feel it.
"Dogs are just like kids: They can be the sources of enormous joy and enormous worry," says Hare, who has two children and two dogs. "But overall, despite the worry and pain, most dog owners I know, including me, would say that there is overwhelming benefit."