Search “pets and health” online and you’ll find thousands of articles claiming that our furry companions can reduce stress, motivate us to exercise more and cut the risk for diseases such as obesity and heart disease. But scientific research on the link between pets and health is actually quite mixed, with recent studies finding that owning certain kinds of pets is associated with an increased risk of dying of cancer, Psychology Today reports.

While studies have shown that having an animal companion can have a number of positive health effects, including reducing blood pressure, improving mental health and preventing childhood allergies, many studies have also shown that pet owners are at greater at risk for illnesses such as hypertension, anxiety, gastric ulcers and migraine headaches.

Now, new research conducted by epidemiologists at the College of Public Health at Georgia Southern University suggests that certain pets may increase some peoples’ cancer risk. Researchers analyzed three studies based on data from the Center for Disease Control and Prevention’s National Health and Nutrition Examination Survey (NHANES) gathered since 1988 that included information on 13,725 individuals who were demographically representative of the American population. About half of them, as it turns out, had pets.

In the first study, published in the Journal of Public Health, researchers investigated the connection between pets and colorectal cancer. They found that pet owners were almost three times as likely as those who did not own pets to have died of the disease. This link was most prominent among cat owners, who had a 2.67 times greater risk of dying of colon cancer overall compared with people who didn’t own cats. For dog owners, however, scientists found no link.

The second study, published in Environmental Research, looked at the link between pets and lung cancer. After adjusting for variables, researchers found no link between pet ownership and male lung cancer deaths, but women who owned pets were more than twice as likely to die of lung cancer than those who didn’t. Interestingly, researchers found no link between lung cancer deaths and dog ownership—just cats.

Finally, a third study, published in the International Journal of Environmental Health Research, looked at cancer risk overall. It found that the risk of dying of any type of cancer was nearly 40% higher for women who owned pets than women who didn’t. The effect was greatest among women who owned birds (2.41 times more likely) and women who owned cats (1.48 times more likely). Once again, male pet owners overall and pet owners of either sex who had dogs were no more likely to die of cancer than people without pets.

So what gives? Researchers speculated that cat and bird owners may come into more toxic chemicals overall than dog owners, as a result of cleaning cages and litter boxes. They also noted that women are generally more susceptible to cancer risks in their environment. That said, it’s possible that these latest studies were a statistical anomaly. And it’s worth noting that other large studies on the potential link have not shown any link between pet ownership and cancer. Indeed, some studies have found that pet owners are less likely to develop one particular type of cancer, non–Hodgkin lymphoma.

So the scientific debate over whether or not pets are good or bad for our health rages on…

For further reading on pets and cancer, click here.