Women infected with the common cat parasite Toxoplasma gondii, which lurks in litter boxes, may suffer undetected brain changes that lead to personality changes and even mental illness. That’s according to a new study of more than 45,000 women in Denmark published Monday in the Archives of General Psychiatry. The parasite, excreted in cat feces, also spreads through undercooked meat and unwashed vegetables. Pregnant women have long been warned to avoid the parasite, because they can pass it onto their fetus, causing brain damage or stillbirth. In the new study, researchers found that women infected by T. gondii were one and a half times more likely to try to take their own lives than those who were not affected. They were also more likely to try to commit suicide violently—with a gun, sharp object, or by jumping, Time reports. Suicide risk increased with the levels of T. gondii antibodies found. “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,” study author Teodor Postolache, an associate professor of psychiatry and director of the Mood and Anxiety Program at the University of Maryland School of Medicine, said in a press statement.