Women who own cats are more likely to commit suicide, but it has nothing to do with the lonely 'cat lady' stereotype, according to new research.

Researchers from the University of Maryland found that women infected with the parasite T. gondii, which can be contracted while changing cat litter, were one-and-a-half times more likely to attempt suicide.

"We can't say with certainty that T. gondii caused the women to try to kill themselves, but we did find a predictive association between the infection and suicide attempts later in life that warrants additional studies," says Teodor T. Postolache, MD, the senior author at the University of Maryland Child, in a press release.

By analyzing the data of 46,000 Danish women, researchers found not only a correlation between increasing levels of T. gondii antibodies and higher suicide risk, but also an increased risk of violent suicide. Previously recorded metal illness did not alter the findings.

All warm-blooded animals can become infected with the parasite and about one-third of the world's population are already infected. Eating unwashed vegetables or uncooked meat and drinking water from contaminated sources can infect humans with T. gondii.

"T. gondii infection is a major public health problem around the world, and many people don't realize they're infected," says Doctor Albert Reece, dean of the University of Maryland School of Medicine.

Postolache says the reason for increased suicidal behaviour was not clear, nor did he exclude the possibility that people with suicidal behaviour were more likely to be infected by T. gondii in the first place.