http://newsinhealth.nih.gov/2009/February/feature1.htm.And for those who might be skeptical about the health benefits that dogs provide, there is a ton of research out there. From NIH,
If you google "health benefits of dogs" or even cats, you can get a lot of info on the scientific studies.
I know a lot of people who have animals for companionship who would be alone without them. The animals give them a reason for getting up each morning, and no matter what study you find, there is no benefit greater than love.