Pets can improve mood, but evidence is thin that they can improve health

Scrappy brought more than floppy ears to the author's family.
Scrappy brought more than floppy ears to the author's family. (Carolyn Butler)
By Carolyn Butler
Tuesday, January 18, 2011; 12:00 AM

I grew up in an apartment building that didn't allow pets, so I was slightly nervous when my husband, Jamie, and I adopted a dog nearly a decade ago. But it didn't take long before the aptly named Scrappy won me over, with her soft, floppy ears, oversize paws, clumsy playfulness and penchant for curling up on my feet. In fact, she quickly became a beloved member of the family, despite her unfortunate habit of running away and rolling around in foul-smelling messes.

Clearly, Scrappy brought a lot of happiness into our home, but Jamie has always insisted that having her around actually made him feel better: less anxious, for one thing, and much more relaxed.

A small body of research suggests that my husband was right. "We know that pets can have a positive health impact on people who feel positively about them," says Erika Friedmann, a professor at the University of Maryland School of Nursing and president of the International Society for Anthrozoology, whose members study human-animal interaction.

Friedmann's seminal 1980 research found that heart disease patients with pets had better one-year survival rates than similar patients without pets. More recently, studies have shown that pet ownership is associated with reduced stress, lower blood pressure, fewer doctor visits, less loneliness and increased social connectivity, and higher levels of physical activity.

Still, the findings haven't all been positive: Research published in a Scandinavian psychiatric journal followed 424 patients admitted to the hospital with acute coronary syndrome and found that pet owners - cat owners, in particular - were more likely to be readmitted or die within a year than patients who did not have cats. And the role of Fido or Fifi in childhood asthma and allergies remains an especially gray area, with some studies reporting that having a family pet early in life can trigger the development of these diseases, and others showing that the presence of an animal is a protective factor.

The confusion continued last fall, with the publication of a long-term study of 636 children in the Journal of Pediatrics. Researchers showed that kids with dog allergies were less likely to develop eczema by age 4 if they lived with a dog during their first year of life. The exact opposite was true for children who were allergic to cats and grew up with a cat in the house: They had a significantly increased risk of developing eczema later on than similar children who had no cat.

There's clearly a need for more - and better - scientific evidence about the link between pets and health.

"There is some good, solid research out there - a lot of tantalizing small studies - but there are also some methodological flaws with evidence for the positive effects of pets," says James Griffin, a scientist at the National Institute of Child Health and Human Development. One major limitation he cites is the difficulty of running "blind" studies, since people know when they are interacting with an animal. "That said, there are also a lot of methodological flaws in [studies] not showing that association or showing negative effects."

NICHD has created a partnership with the Waltham Centre for Pet Nutrition, a division of McLean-based foodmaker Mars, to encourage better research on human-animal interaction; there are currently seven such studies underway. "We need to know what are the underlying mechanisms that are actually behind these potential health benefits," says Griffin.

He notes, for example, that early research suggests a possible release of the hormone oxytocin, which can lower stress hormone levels, when people are around their dogs and possibly other pets. "This shows that at the physiological level, there's a response that corresponds with the bond people feel with animals. It's also related to stress reduction, which is thought to be what underlies some of the strong findings with the cardiovascular system, like heart attack recovery. . . . But we need to know more."

Griffin points out that one factor that must be considered is the actual relationship between a pet and its owner. "If you don't like the cat in your household, it is very unlikely that cat is going to reduce your stress levels, versus if you're very attached - it lays in your lap and you pet it - it's probably much more likely to have that effect," he explains.

But what about potential health hazards? Experts say the biggest issue is bites, although there are also a range of diseases that can be transmitted from pets to people, including worms, toxoplasmosis and cat scratch fever. A study published online in Pediatrics last summer demonstratedthat humans contracted salmonella from contaminated dry dog and cat food between 2006 and 2008, with nearly half of the cases found in young children.

"The risks are there, but they are relatively small," says Sandra Barker, a professor of psychiatry and the director of the Center for Human-Animal Interaction at the Virginia Commonwealth University School of Medicine. She notes that immune-compromised people should not have turtles and birds and may need to take extra precautions with other animals, but otherwise "common sense and appropriate hygiene go a long way towards preventing any problems: Just wash hands, wash hands, wash hands, and especially wash children's hands."

What can be far more difficult to deal with - and have a much larger impact on emotional health and well-being - is losing a treasured pet, says Barker.

That's something we discovered firsthand last fall, when Scrappy was hit by a car and died. I didn't stop crying for a week, and I'm still tearing up just writing about it. But one thing the experience has taught me is that Scrappy absolutely did make our household a calmer, more relaxed place. Our relationship was uncomplicated and unconditional, and I know now that, like my husband, I truly felt better when that sweet mutt was around.

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