In a stressful situation, you may be better off with a pet at your side than with a friend or spouse, a new study suggests.

"We've documented that people see their pets as important sources of social support," says the study's lead author, Karen Allen, PhD, a research professor at the State University of New York at Buffalo.

Previous studies have shown that pet ownership can reduce stress and even lower mortality rates after heart attack, but this is the first study to include hundreds of participants of both sexes, a variety of psychological and physiological measures and the use of two acute stressors--rapid serial subtraction and the immersion of a hand in water.

The researchers found that the presence of a pet mitigated the effect of the stressors on heart rate and blood pressure and hastened recovery to baseline levels. Pets also helped to lower their owners' baseline levels of cardiovascular arousal and increased the likelihood that they would describe the stressors as "challenging" instead of "threatening."

Both pet owners and nonowners showed the highest levels of cardiovascular reactivity in the presence of their spouses, especially during the mental arithmetic task. Nonpet owners were least reactive when they were alone, while pet owners were least reactive in the presence of their pets.

The authors suggest that pets lower stress by providing nonjudgmental companionship--support that can be difficult for even the most encouraging spouse or friend to provide. "No matter how much we believe that person's on our side, there's always an evaluative side to it," says Allen.

Interestingly, pet owners showed intermediate levels of stress when both pets and spouses were in the room. "The pet seems to cancel out some of the edge when you're under stress," says Allen.

"It's almost as though, if you have to have a spouse--and I think having one is a good idea--then having a pet probably wouldn't be a bad idea either," she added.

Previous studies have focused primarily on dogs, but this study included cats as well in order to determine whether the "aloof, impersonal behavior of cats," as the authors described it in their paper, limits their ability to buffer stress. Contrary to the stereotype, there were no significant differences between the effects of cats and dogs on their owners' stress levels.

One limitation of the study was that baseline levels of arousal differed between pet owners and nonowners. The difference could be due to the stress-reducing effects of pets, but it could also be caused by pre-existing differences between pet owners and nonowners, or by another variable correlated with ownership.

The study appears in the September/October issue of Psychosomatic Medicine (Vol. 64, No. 5). It was co-authored by Jim Blascovich, PhD, a professor of psychology at the University of California, Santa Barbara (UCSB), and Wendy Berry Mendes, PhD, a former UCSB graduate student who is now a postdoctoral fellow at the University of California, San Francisco.