This overview of the relationship between humans and companion animals mentions various studies and presents an overview of current research.

In one notable study, the University of Minnesota found that cat owners were 40% less likely to die from heart attacks than non-cat owners. They were also less likely to die from all cardiovascular diseases, even taking into account other heart disease risk factors including age, weight, gender, race, ethnicity, smoking, and cholesterol levels. Canine companionship did not convey the same health benefits.

In California, researchers recently found that people in the San Francisco area who reported having owned a companion animal had about a 30% lower risk of developing non-Hodgkin’s lymphoma, a cancer of the body’s blood-filtering tissues, compared with non-companion animal owners. The longer they owned a companion animal, the more protection they appeared to have.

Earlier studies have linked companion animal ownership during infancy with a reduced risk of asthma and allergies, because that exposure to companion animal dander is believed to desensitize the body toward later contact with allergens. Now, the California researchers theorize a similar chain of events with non-Hodgkin’s lymphoma.

More recently, the Center for the Human-Animal Bond at the Purdue University School of Medicine found additional benefits, including that the presence of a fish tank helped focus the attention of Alzheimer’s patients who tend to pace and wander at mealtime.

Finally, in another study by the Research Center for Human Interaction at the University of Missouri, researchers found that dogs are more likely to inspire elders to stick with a walking program than two-legged (human) companions.