Dogs are know to be big stress reducers and medical studies have shown that dog owners have lower blood pressure. Petting a dog that comes over and cuddles with you, or taking your dog for a walk keeps people active and happy.
“We once had to argue why this was a valid focus to conduct research,” says Alan Beck, director of the Center for the Human-Animal Bond at Purdue University in West Lafayette, Ind., a pioneer in the field. “Today, the National Institutes of Health and science in general recognize the overall value of pets.
“What we're embarking on now is to better understand why animals have such an intrinsic value and how to use this relationship in relation to children and our aging population.”
There have been many studies regarding the chemical levels between dog owners and non-dog owners. "In her book For the Love of a Dog, Patricia McConnell, a certified applied animal behaviorist, writes that levels of oxytocin, a mood-affecting neurotransmitter and “feel-good” hormone in the brain, increase by merely petting a dog."
Scientist are trying to figure out why this is happening and what causes these stress levels to decrease.
According to Steve "Results of a decade-long study suggest cats may have special health-sustaining qualities, which is probably no big surprise to Americans, who own more cats than dogs. For 10 years, Adnan Qureshi, professor of neurosurgery and neurology at the University of Minnesota, followed 4,500 people and in 2008 announced his study's intriguing conclusions: Those who owned a cat were 40% less likely to die from heart attacks than those who had no feline in their lives. Owning a dog did not appear to convey the same protection. That statistical result is so far unexplained, Qureshi says. Other factors may contribute to the difference."
Steve also found that "Several studies have shown that dogs encourage people to exercise (that's good for the heart, of course), but cats have at least one talent no dog has: They purr. Why they purr isn't completely understood; cats purr when they're content, but they also purr as a way to soothe themselves, to relax kittens and probably to lower their own anxiety when they're sick or under stress."
Could it be that their purring is also soothing to people in ways we don't understand? Qureshi thinks so and is about to study the phenomenon. But measuring purring's importance is challenging. “Is it the purring that matters,” he wonders, “or the mere presence of the cat, petting the cat or a combination?”