Women infected with a parasite spread by cat faeces run a higher risk of attempting suicide, suggests a study of more than 45,000 women in Denmark published in a scientific journal this week.

"But we did find a predictive association between the infection and suicide attempts later in life that warrants additional studies. We plan to continue our research into this possible connection."

About one in three people in the world are believed to be infected with T. gondii, which has been linked to schizophrenia and behavior changes, but often produces no symptoms as it lurks in brain and muscle cells.

Humans run the risk of infection when they clean out their cats' litter boxes, as well as by consuming unwashed vegetables, undercooked or raw meat, or water from a contaminated source.

"The study found that women infected with T. gondii were one-and-a-half times more likely to attempt suicide compared to those who were not infected, and the risk seemed to rise with increasing levels of the T. gondii antibodies," a summary of the findings said.

"Previous mental illness did not appear to significantly alter these findings. The relative risk was even higher for violent suicide attempts."

The suspected perils of T. gondii featured in The Atlantic magazine in March this year when it ran a widely-read profile of Czech biologist Jaroslav Flegr, who suspects the parasite of literally changing people's minds.

It headlined the article: "How Your Cat is Making You Crazy."