Happy pets make happy people.

Diane Macdonald/Getty Images

Pets are a big responsibility. Not only do they demand regular meals and a steady supply of fresh water, but they have to be cleaned up after constantly, too. Depending on the species, they may also require frequent walks, a steady supply of mice or a daily changing of the newspaper at the bottom of their cages. Caring for a pet is like raising a child but without the eagerly awaited emancipation stage.

Yet despite the tedium, an astonishing number of furry, scaly or creepy crawly critters have managed to work their way into our homes. In the United States, 63 percent of households harbor at least one pet. That works out to approximately 71.1 million homes and an astonishing 382.2 million animals [source: American Pet Products Association]. They're not cheap, either: According to the American Pet Products Association, pet owners will spend upward of $45.4 billion on pet charges in 2009.

So what's the justification for this madness? With all the attention and money lavished on them, what do pets offer in return? Well, plenty, actually. Pets are a pretty wise investment. It appears that what pet owners sacrifice in terms of time and money, they get back in better health and increased happiness. Sure, you pet owners out there have known your pets make you happy all along. But now a growing body of research is here to back you up.

The pet Rx appears to work in a number of ways. For one thing, pet ownership tends to prompt people to adopt a multitude of healthy behaviors. Take a pet's need to be fed and taken outside every few hours, for instance. That responsibility gives pet owners purpose and makes them feel needed, improving their senses of self worth. It also forces them to get off the couch and go for a walk every now and then, boosting both health and happiness.

Besides the behavioral changes, studies also show that interacting with a pet helps to reduce levels of harmful neurochemicals in the body and raise the good ones.

So is Fido a dog or a furry-coated Prozac? It's a valid question, and we'll answer it on the next page.