Why Do Human Friends (But Not Pets) Make People Live Longer?

Every year, researchers who study human-animal relationships get together at the annual meeting of the International Society for Anthrozoology (ISAZ for short) to schmoose and trade the results of our latest studies. This year’s meeting was in Chicago, and one of the keynote addresses was by the psychologist Louise Hawkley. Her talk spun my head around. And it has caused me to question my belief that our pets are, literally, our friends.

Hawkley studies the effects of loneliness and social connections on human health. In her ISAZ talk, she made the case that socially isolated people die sooner than people who have friends. (This article summarizes some of her findings.) She is right. An article in the journal PLOS summarized the results of 148 studies of the effects of social isolation on human mortality among 300,000 people. The effects of not having a social network on your chance of dying an early death are surprisingly high. Indeed, people without friends have a 50% greater mortality rate than people with strong social networks.

Why was I was so surprised by these findings? Because, in contrast with having human friends, living with a pet doesn’t seem to have any effect on overall human mortality rates. True, some studies have found that pet owners are more likely to survive heart attacks. And a recent report by a high-powered working group of the American Heart Association concluded that dogs may convey some protection to their owners from cardiovascular disease. But as the authors of the AHA report stated, pet owners, on average, do not seem to live any longer than non-pet owners. (See, for example, here.)

The Mystery

Thus the mystery -- why should human companionship be so highly related to our longevity while living with a companion animal is not? After all, many people think of their pets as friends. Indeed, in a recent Harris poll, 91% of pet owners said they considered their pet to be a member of their family. And a 2008 survey found that two out of three pet owners said they would prefer to be stranded on a desert island with their dog or cat than with their present human partner.

However, I recently ran across a 2010 study by professor Hawkley and her University of Chicago colleague John Cacioppo that suggests the people who prefer to live on a desert island with their pet are making a big mistake. As part of a long-term investigation of impact of social relationships on health in a group of Chicago adults, Hawkley and Cacioppo assessed the relationship between the social connections and psychological well-being. The psychological well-being factors they measured included self-esteem, loneliness, isolation, depression, and general satisfaction with life. The subjects were also asked how satisfied they were with their relationships with: (a) the most important person in their life, (b) their most important social group, (c) God, and (d) their pet.

The results were fascinating. The participants’ satisfaction with their best friend and their most important social group was positively related to the all the indexes of psychological well-being. No surprise there. The shocker was that degree of satisfaction with companion animals was completely unrelated to the measures of well-being – not self-esteem, nor loneliness, nor sense of isolation, nor levels of depression, nor life satisfaction. In other words, having human friends made substantial differences in the participants’ happiness and well-being. Satisfaction with companion animals had no effect. Zip.

Perhaps I should not have been surprised. This is not the first study to show that when it comes to loneliness and health, pets are not panaceas. For example, this study found no differences in loneliness or health of elderly Australians who owned or did not own pets. This study in the journal Anthrozoös found that individuals who acquired a pet were just as lonely six months after they got their companion animal as they were before they brought a pet into their lives. And the American Heart Association working group recommended that people not acquire pets in hopes of reducing their risk of heart attacks.

My feline friend Tilly.

My feline friend Tilly.

The Paradox

A picture seems to be emerging, but I can’t quite put my head around it. Some excellent studies have found that interacting with pets can reduce stress in their owners (here, here, and here), and the notion that pets enhance our quality of life seems intuitively obvious.As I write this, my wife Mary Jean is away for a couple of days at the beach with her long-time social network of gal pals. So it’s just me and our cat Tilly, home alone. Tilly is sitting next to me in an arm chair. Every now and then she meows, the signal for me to rub her belly. A few minutes ago, I asked her if she wanted to go out on the porch. She yawned.

Tilly makes the house seem less empty, less lonely. And like nearly every pet owner, I feel like she is my companion. Yet, after hearing Dr. Hawkley’s ISAZ talk and reading the scientific findings on the importance of human social connections to longevity and loneliness, I am starting to think that there is a big difference between our human friends and our animal “friends”. Sure, both a human friend and a dog or cat can provide solace, a sympathetic ear, and somebody to love. But the differences of the effects of human versus animal companions on human mortality rates appear to be large and real.

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Though I have a few ideas, I am not really sure what people get from their real human friends (as opposed to, say, Facebook “friends”) but not from their pets. While, I hate to say it...”More research is needed.”

PS: In the Hawkley and Cacioppo study, “satisfaction with God” did not fare any better than “satisfaction with pets” when it comes to improving their subjects' psychological well-being.

PS: While living with animals will probably not make you live longer, not eating them will. (Here is the evidence.)

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To learn more about anthrozoology (and why it is not the study of ants) read this excellent post by Scientific American blogger and dog researcher Julie Hecht.

For more on the effects of pets on human health, see these Animals and Us posts:

-Puppies, Kittens, and Human Health: Science Versus Wishful Thinking

-Will Getting a Pet Make You Healthier?

-Do Pets Prevent Sudden Deaths In Children With Epilepsy?

Hal Herzog is author of Some We Love, Some We Hate, Some We Eat: Why It's So Hard To Think Straight About Animals.