|© Chris Reynolds (via Wikimedia Commons)|
You don't need to run any scientific studies to see one obvious health benefit of pets -- increased exercise. Most dogs love physical activity. Taking your dog for a walk or playing fetch with her in the park helps YOU get some physical activity in as well. Even though most cats aren't amenable to the idea of going for a walk, a few will eventually accept a harness and will enjoy exploring the yard with you. I even once met a lady who would put a harness on her pet parrot and let him ride on her shoulder as she walked around the block. She got exercise, and her bird got some beneficial natural sunlight. Even doing simply daily pet care chores such as feeding the little guys and cleaning up after them forces us to get off our butts and move a little.
Animals seem to have a knack for knowing when we need them, and cuddling with a pet always helps when we're stressed or upset about something. Studies have shown that our bodies actually go through changes when we're with our animals. Our levels of cortisol, a stress hormone, is lowered, and we produce more serotonin, which gives us that feeling of well-being.
Of course, if we feel better mentally and emotionally, we aren't as likely to succumb to the physical effects of stress (tension headaches, backaches, high blood pressure, increased risk of heart attack, lowered immunity, and so on). This all goes along with research that shows pet owners are less likely to die from heart attacks or strokes, have lower blood pressure and cholesterol, have stronger immune systems, and are more likely to recover from catastrophic illness.
If you don't have a pet, you may want to consider adopting one. It'll benefit both of you!