Women infected with the common kitty litter parasite called Toxoplasma gondii (T. gondii) could be at increased risk of attempting suicide, according to a huge new study done on women in Denmark.

T. gondii is a parasite often found in cat feces. It’s the reason why pregnant women are advised not to change the litter box while pregnant, because the toxin can lead to brain damage in their developing fetus.

About one-third of the world's population is infected with the parasite without having any symptoms, but some develop a full infection called toxoplasmosis.

Studies have shown that the illness can lead to changes in the human brains; some have even linked it to schizophrenia.

Now, a new study finds that there might be a link between infection with T. gondii and suicide among mothers.

The University of Maryland psychiatrist who is the senior author of the study says at this point, they have only drawn a link between T. gondii and suicide.

"We can't say with certainty that T. gondii caused the women to try to kill themselves,” Dr. Teodor T. Postolache, the director of the Mood and Anxiety Program at the University of Maryland School of Medicine, said in a statement.

“But we did find a predictive association between the infection and suicide attempts later in life that warrants additional studies.”

For the study, researchers looked at 45,788 women in Denmark, who gave birth between May 1992 and January 1995 and whose babies were screened for T. gondii antibodies.

Since babies don't produce antibodies to T. gondii for three months after they are born, if they had the antibodies, it meant they had picked it up from their infected mothers.

The scientists then scoured Denmark’s health registries to determine if any of these mothers later attempted suicide. They also cross-checked Danish psychiatric records to see if the women had been diagnosed with mental illness.

They found 517 women who attempted suicide during 14 years of follow-up, including 18 who succeeded in killing themselves.

Those women who were infected with T. gondii were one-and-a-half times more likely to attempt suicide compared to those not infected. What’s more, the risk seemed to rise with increasing levels of the T. gondii antibodies.

Interestingly, previous mental illness did not appear to significantly alter these findings.

The relative risk was even higher for “violent” suicide attempts, including those involving sharp instruments, guns, and jumping from high places.

Since only 18 women actually committed suicide, it was too small a number to assess the possible impact of T. gondii infection on their death risk.

The full results appear in the Archives of General Psychiatry.

The authors say it’s possible that there are risk factors for suicidal behaviour that also make people more susceptible to infection with T. gondii.

But he says if it can be determined that T. gondii raises the risk of suicide, there might be ways to intervene or offer treatment.

In the meantime, there are ways to prevent T. gondii infection, which can also be picked up by eating undercooked or raw meat, unwashed vegetables, or drinking water from a contaminated source.

They include cooking meat thoroughly, washing all vegetables and routine kitchen hygiene to avoid spreading the parasite.