When you look at the facts, the jury is still out on this popular theory
By Hal Herzog, Ph.D.
While writing Some We Love, Some We Hate, Some We Eat: Why It’s So Hard To Think Straight About Animals I learned some things that really surprised me. For example, the evidence that pets enhance human health and psychological well-being (the so-called “pet effect”) is weaker than I thought.
I can hear the howls already. If, like me, you’re a pet lover, you’re probably convinced that your pets make you a happier and healthier person. Like most people, I thought “the pet effect” was a firmly established scientific fact.
I’d read books like Marty Becker’s The Healing Power of Pets, and a host of newspaper and magazine articles on the psychological benefits of pet ownership. Further, Marc Bekoff, Stanley Coren and Allen McConnell , all excellent scientists, have promoted the health benefits of pets.
I had also encountered many scientific journal articles that began with a statement like “The health and psychological benefits of pets on human physical and psychological health are now well-established.” And I’d heard a slew of conference presentations on “the pet effect.”
But when I started doing the research for the pet chapter in my book, I sorted the scientific journal articles I had amassed into three stacks based on their results—the “good” pile, the “bad” pile and the “ugly” pile. I was shocked by what I found.
First, the Good News
The good news is that a lot of studies (the “good” pile) found that health and psychological benefits do accrue from living with animals. Indeed, the field of anthrozoology (the study of human-animal relationships) was jump started by Erika Friedmann’s groundbreaking study showing that the one-year death rate of heart attack victims who had pets was one fourth that of people who did not live with companion animals.
In the three decades since Erika’s study, other benefits of pets on health and psychological well-being have been documented by researchers. These include lower blood pressure and psychological stress, decreased doctor visits and missed days of work, better sleep, increased self-esteem, decreased loneliness and depression, healthier attachment styles, and higher levels of physical activity.
Now, the Bad News
But as I began to collect more and more articles on pets and health, I was surprised at the number of studies that found there were no differences in the health or happiness of people with pets and people without pets.
Further, this “bad” pile of articles kept getting bigger and bigger. Among these were studies reporting that pet guardianship was NOT associated with decreased psychological stress, blood pressure, heart rate, or depression. Nor was it associated with increased levels of happiness, life satisfaction or exercise. And I could find no evidence that people with pets lived longer.
Finally, the really bad news
Then there was the “ugly” pile the studies that found that pet guardians were actually worse off than people without pets.
(Note: This pile did not include the studies of pet-induced injuries – for example, the 85,000 people each year who are taken to emergency rooms because of falls caused by tripping over their pets, or the 800,000 individuals, mostly children, who receive medical attention for dog bites, or the fascinating array of diseases people can contract from pets, such as MRSA, salmonella, hookworm, toxoplasmosis and cat-scratch fever.)
The ugly pile consisted mostly of epidemiological studies in which pet people were found to be at greater risk than non-pet people for problems such as depression, anxiety, panic attacks, chronic tiredness, insomnia, obesity, hypertension, gastric ulcers, high cholesterol, and migraine headaches.
There is, of course, no evidence that pets are the CAUSE of these problems – just as there is little real evidence that pets cause better health. (I discuss the problem of conflating causality and correlation in this article on pets and health.)
Nonetheless, one study found that pet owners had elevated diastolic blood pressure, higher BMI’s and were more likely smoke cigarettes.
And then there is the 2010 study of how heart attack victims fared a year after their initial coronary. After taking demographic and basic health differences into account, the researchers discovered that the pet owners in the group were twice as likely as non-pet owners to have either died of a heart attack or to have been readmitted to the hospital for cardiac problems. Ouch!
The Bottom Line
But, you ask, if the research on the “pet effect” is such a muddle of inconsistency, why do so many people believe it is an established scientific fact?
One reason is that we want to believe that our pets are good for us. Another is that the media loves “feel good” animal stories, yet usually ignores studies that do not support the pet effect hypothesis. In addition, the $50-billion dollar-a-year pet products industry is pushing the idea that a sweet little Yorkie can lower your blood pressure, make you lose weight, and drive away the blues.
The bottom line, however, is that despite 30 years of research, “the pet effect” is not an established fact but an as yet unsubstantiated hypothesis.
I will discuss some reasons why the studies on of pets on human health and happiness are so inconsistent in my next post. But right now, my cat Tilly is meowing. She wants me to stop writing and play a round of “chase the laser pointer red dot.”
For references to the research described in this post and more detailed discussions of the pet effect research literature, see Chapter 3 (“Pet-O-Philia: Why Do Humans –and Only Humans – Love Pets) in my book on human-animal relationships or this draft of my article on pets and human health in the August 2011 issue of Current Directions in Psychological Science.
Hal Herzog is a psychologist at Western Carolina University whose research focuses on our attitudes towards and interactions with other species. His book Some We Love, Some We Hate, Some We Eat: Why It’s So Hard to Think Straight About Animals is published by HarperCollins.