"While the idea of a pet as social support may appear to some as a peculiar notion, our participants' responses to stress, combined with their descriptions of the meaning of pets in their lives, suggest to  us that social support can indeed cross species," says lead study author Karen Allen, Ph.D., of the State University of New York at Buffalo.

Researchers evaluated participants' responses to two tasks known to induce stress: mental arithmetic problems and tasks requiring participants to submerge one hand in ice water for two minutes. An electronic monitor recorded participants' baseline heart rate and blood pressure, then measured them once each minute during the tasks. In addition, the number of errors during the math task was recorded. Before each task, the participants were asked to rate whether they saw the task as either "challenging" or "threatening."

Pet owners had significantly lower baseline heart rate and blood pressure than the participants who did not have pets; moreover, they had lower "reactivity" to the stress tests and returned to baseline levels more quickly. 

Pet owners also made significantly fewer errors during the mental arithmetic challenge, while participants who performed the tasks with just their spouse present tended to make the most errors.

In addition, when asked to describe the tasks as either "challenging" or "threatening," pet owners with their pet present were more likely to describe the task as challenging than those who performed the tasks in the presence of spouses or friends. 

Separate studies were performed for dog and cat owners, but because the researchers found no significant differences between the two types of pet owners, the data were analyzed together.

According to Allen, "the findings demonstrate that pets can buffer reactivity to acute stress as well as diminish perceptions of stress." 

The authors suggest that because participants demonstrated the lowest stress response when they were alone or when they were with their pets,  participants' perceptions of whether their spouse or friend was judging or evaluating their performance could have played a role. 

Other studies over the past 20 years has revealed a number of health benefits derived from animal companions. For example:

Older people with pets were more active and less likely to be depressed than their peers without pets. 

Pet owners with AIDS were less likely to be depressed than those without pets. 

Stockbrokers with high blood pressure who adopted a pet were better able to control their high blood pressure than stockbrokers without pets. 

People with pets have been shown to have lower cholesterol and blood pressure, reducing the risk of heart disease. 

Businesses that allow pets in the workplace found that employees believe that the animals reduce stress and improve their mental and physical health. 

Pet owners see doctors less often than those who don't own a pet.