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This Is What Your Brain and Body Do When You Hang Out With Animals

Here’s everything we know about how pets affect your mood.
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Most people adopting a dog expect furry affection and bright-eyed companionship. Ingrid Pipes is looking for that and something a step above.

Pipes, a 27-year-old copywriter in Pittsburgh, and her husband recently adopted Hudson, a miniature Bernese mountain dog/poodle mix, with the intent of enrolling the puppy in an obedience school that will train and certify him as a therapy dog to help treat Pipes’ depression.


“Mostly, his job would be to see signs of sadness and depression and get my attention to distract me,” she says, “like bringing me one of his toys to play, or sitting in my lap and asking to be pet.” He will be more responsive and interactive in the presence of human distress. Pipes found a few services in the Pittsburgh area that provide such training. (Some trainers even prepare pups to relieve anxiety by using their paws to put gentle pressure on a human's chest.)

“I have high-functioning depression,” Pipes says, “so I usually make it to work, can do my chores and whatnot, but it’s always there.”

She hopes Hudson can fulfill the role of DJ, their recently deceased chow-chow. While not a trained therapy dog, DJ was a natural. “[H]e was good at distracting me,” she says. “He would lay at my feet and follow me around the house, calmly and quietly. He was the perfect shadow and never gave me a minute alone, but also would be cool with whatever we wanted to do.”

Pipes worried about relaying her stress onto a new puppy, so she sought training that would allow Hudson to thrive in occasional atmospheres of gloom and dispirit. “Some dogs definitely just get it,” she says. “If you're feeling sad, they know to come to you. The reliability of companionship is a big part of it because your dog is molded to your schedule. They're never going to be too busy to take your call. If you train your dog right and treat them nicely, your dog is going to love you and need you, even if you're failing in every other part of your life.”


Research has consistently shown that animals, particularly dogs, provide psychological benefits for humans—although the exact reasons are not known. “It’s a popular topic right now,” says Lori Kogan, a professor at the College of Veterinary Medicine and Biomedical Sciences at Colorado State University and editor of The Human-Animal Interaction Bulletin, the journal of the American Psychological Association’s group dedicated to that topic.

“People are trying to validate what people already know: that animals make us feel better.” As researchers attempt to parse out why and how animal-assisted therapy works on the human brain, debate continues about if pets should be considered a valid healthcare treatment or disability issue.

The connection between pets and oxytocin

One lab result has been consistent: When interacting, humans and their pet dogs both experience increased levels of oxytocin, a “love hormone” that is also triggered by hugging, orgasm, and lactation. Oxytocin helps the brain modulate social concepts, such as empathy, trust, and in-group preference and memory of social cues. The chemical lets you know when you should take comfort in others. It surges when people see their parent or child—sometimes doubling in a parent when reunited with a young child.

It also works cross-species: Dog owners experienced an average oxytocin boost of 6.6 percent after scratching and petting their canine companions, in a 2014 Swedish study that measured the effect in real-time. Canine contact also causes a decrease in levels of cortisol, a hormonal alarm system for stress, in humans.


If spikes in oxytocin reveal how much humans love dogs, they really show how much dogs love humans. Dogs experience a 57-percent increase over baseline levels of oxytocin when playing with their humans.

Oxytocin levels also increase the chances a dog will turn to their human for help. Another Swedish study gave a set of golden retrievers the impossible task of getting a treat in a tightly sealed jar. Some of the dogs got a hit of oxytocin via a nasal spray beforehand. Those dogs tended to approach their owner for help more often, compared to a control group that inhaled a neutral salt water solution. Other dogs given an infusion of oxytocin were more likely to make eye contact with friendly faces in photos and ignore threatening ones, a Finnish study documented. These studies show the brain chemical plays a role in the interplay of affection and receptivity between the two species.

In 2016, a BBC2 documentary ventured into the little-explored area of brain chemicals in pet cats, hiring a lab to compare oxytocin changes in both species when cats interact with people. While the chemical did increase in the felines, the change was much less than it was in canines (a result that should surprise no one who has interacted with both species). Oxytocin increased by an average of 57 percent in dogs when playing with their humans, but only by 12 percent in cats. There haven’t been any studies testing the oxytocin effect of humans interacting with cats, and feline-related research is scant compared to studies of the impact of dogs.


The benefits of animal-assisted therapy

If you are looking for evidence that animals make people feel better, particularly when they are distressed, there are seemingly endless examples: Therapy dogs were shown to have reduced anxiety in people hospitalized with depression in Germany and did the same for long-term residents of a senior home in South Africa.

They were also a pacifying presence in a pediatric center, according to a Brazilian study. In patients, the presence of therapy dogs decreased pain, irritation, and stress and other depressive symptoms. Caregivers also felt less anxiety, mental confusion, and tension.

John Hopkins Hospital in Baltimore has allowed therapy dogs into several departments, including the intensive care unit, as a “nonpharmacological intervention.” The hospital has kept up with a shift in critical care—from keeping patients sedated to allowing them to be awake and engaged as soon as possible, says Megan Hosey, a psychologist specializing in rehabilitation at the hospital.

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“When [patients] are awake, there is a need to take care of them on a deeper level,” Hosey says. “As clinical psychologists, what have observed in other settings is that dogs provide wellbeing. Patients that are partnered with a dog might get to walk the dog or give the dog a treat. That gives them a purpose, and we know that there is good data to support that dogs help patients with their mood.”


There is no overarching theory as to why dogs are such mood-boosters. Hosey speculates that well-trained canines show emotional consistency, which could help a person in distress stabilize their own equilibrium. The benefits could also be as simple as reducing loneliness and giving the person something on which to focus besides their own condition.

Limitations of the research

The exact mechanism of the benefit of human-animal interaction may be foggy because the study of it is faulty, according to Hal Herzog, professor of psychology at Western Carolina University. He became concerned about the state of animal-assisted therapy research when writing his book, Some We Love, Some We Hate, Some We Eat: Why It’s So Hard to Think Straight About Animals. “Ninety-five percent of publications showed a positive result and that was just too good to be true,” Herzog says.

Many studies simply show the efficiency of one program and those that don’t have a positive result tend not be publicized or, in some cases, even published. He points to the doctoral thesis of one researcher, Alisa Greenwald. She studied the impact of a therapeutic horse riding program on 81 emotionally disturbed boys in a residential treatment center while earning her doctorate at Pace University in New York. Greenwald found it had no significant effect on the kids’ self-esteem or frustration tolerance. Although the study, completed in 2001, had “a reasonably large sample size,” according to Herzog, it was never published.


Studies trying to show the effectiveness of animal-assisted therapy are often plagued by small sample sizes, lack of control groups, and failure to control for expectancy effects, Herzog says. The methods that scientists use to create consensus, such as trying to replicate results and including a control group, are rarely employed.

“Part of animal-assisted therapy is that a person comes in with the dog regularly,” Herzog says. “Maybe it’s the dog or maybe it’s the person. Maybe it’s just getting attention regularly.”

He admits that there is some challenge in applying the usual scientific rigor to animal-assisted therapy. “How do you come up with a placebo for a dog?” he asks. “I don’t know that.”

The problem, Herzog says, is that there is a mismatch between what we know and what people think we know. "People want to think that animals are miracle workers,” he says, adding that comparisons between animal interaction and more tested medical treatments—like drugs or physical therapies—are not apt. There just isn't the same kind of scientific scrutiny applied.

Pets as a scientifically tested health remedy is the exact message pushed in some materials from the Human Animal Bond Research Institute. HABRI began in 2010 to act as a funder and hub for research on human-animal interaction and has spent $2 million and approved 26 research projects for funding. For its “The Pet Effect Campaign,” the organization created parodies of prescription drug commercials encouraging adoption of cats and dogs for relief from a litany of health problems.


“I found a way to relieve my depression,” says a voice matched with familiar sunny stock video-looking footage. “I found a way to lower my cholesterol,” explains another. “I found a way to strengthen my immune system. I found better health, with cat!” These is even a side effects rundown (“difficulty breathing because a cat is sleeping on your face, difficulty working because your cat is on your computer, issues packing because a cat is in your suitcase…”). The video ends with a suggestion to “discover better health; ask your veterinarian about cat.”

Pet Effect brochures, posters, and flyers link pet ownership to better management of autism, blood pressure, cardio health, depression, post-traumatic stress, obesity, and childhood allegories—usually without citing specific studies.

One reason this campaign seems similar to prescription drug marketing is that the effort is led by Zoetis, one of HABRI’s sponsors and a producer of medicine and vaccinations for pets and livestock. Zoetis is a former subsidiary of Pfizer, a pharmacological juggernaut that’s mastered slick TV advertising.

Other HAMBRI sponsors have a financial incentive to encourage pet ownership, a $72 billion industry in the US. Among them are the American Pet Products Association, Petco’s charity arm, and PetSmart. Steven Feldman, HABRI’s executive director, says funding and promoting this research is a natural act of corporate philanthropy for these businesses. “There is always a need for research and for more and better research,” Feldman says.


HABRI has a scientific advisory board that approves the research projects it funds and ensures the efforts it supports are driven by scientific interest and validated by standards, Feldman says. “We are most interested in studying the scientific benefit,” he says but “the research will lead where it leads.”

He adds that HABRI’s scientific leadership is aware of “some of the gaps” in animal-assisted therapy research and one of the organization’s purposes to is to help fill them. As for the videos, he notes that some prescription drugs that had been widely used have later been shown to be ineffective. “Veterinarians really like to show the videos," he says.

The rise of emotional support animals

Perhaps the trend that most shows the medicalizing of pets is the increase in “emotional support animals.” ESAs, unlike therapy dogs (such as Pipes’ miniature Bernese mountain/poodle mix), require no special training for the designation. All they need is a statement from a mental health professional stating that the animal is beneficial to a patients’ wellbeing. This concept came to public awareness rather ostentatiously last January when United Airlines barred the “emotional support peacock” of a New York City performance artist from a flight.

ESA designation allows pets to bypass certain transportation and housing bans on animals via federal disability law. ESAs exist at the crossroads of psychology, handicapped rights, and public policy, making them an awkward subject for any one of the above. “It’s a big topic,” Kogan says. “College campuses are struggling with what to do with it. They are allowed in dorms and rental properties.” She adds there is confusion among housing and transportation providers and the general public and even some psychologists about the difference between these animals and trained working animals.

The federal Department of Transportation has said that disability-related complaints about service animals nearly quadrupled from 2012 to 2016, signaling an increase in the use of the “emotional support animal” designation. (American Airlines has a hilarious list of stipulations on them, precluding ferrets, goats, hedgehogs, and miniature horses not trained as service animals.)

Kogan says that—given the benefits of animal-human interaction in general—researchers are not sure “how emotional support animals are different,” she says. “There is not a clear distinction between them and pets.”

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