Several studies have been done to better understand the relationship between health and pet ownership. Dr Deborah Wells in an article published in the British Journal of Health Psychology reported that dogs owners in particular tend to have lower blood pressure, cholesterol, healthier overall and have fewer minor ailments and serious medical problems when compared to the general population.

Another study focused specifically on pet ownership and hypertension. A group of 48 New York stock brokers with hypertension were placed on ACE inhibitor therapy (lisinopril) and half of them got either a cat or dog. Resting blood pressure for the two groups throughout the experiment followed virtually the same course, with significant drops in both systolic and diastolic blood pressure. However, those who had acquired pets had much lower blood pressure and heart rates during times of stress, about 8 to 13 mmHg systolic and 5 to 10 mmHg diastolic. The study hypothesized that it was the increased social support offered by a cat or dog that led to the more stable lower blood pressure.

Sources:

“Dog-owners ‘lead healthier lives’ ” BBC News. Sunday, 21 January 2007. Can be viewed online at http://news.bbc.co.uk/2/hi/health/6279701.stm

“Home Blood Pressure Responses to Mental Stress” Karen Allen, Barbara E. Shykoff, Joseph L. Izzo, Jr. Hypertension 2001;38;815-820. Can be viewed online at http://hyper.ahajournals.org/cgi/reprint/38/4/815.pdf
Further information can be found at http://news.bbc.co.uk/1/hi/health/6279701.stm and http://hyper.ahajournals.org/cgi/reprint/38/4/815.pdf.