Women who own cats are more likely to have mental health problems and kill themselves because they can be infected by a common parasite that can be caught from cat litter, a study has found. Researchers found women infected with the Toxoplasma gondii (T. gondii) parasite , which is spread through contact with cat waste or eating undercooked meat or unwashed vegetables, are at increased risk of attempting suicide. The study involved more than 45,000 women in Denmark. About a third of the world's population is infected with the parasite, which hides in cells in the brain and muscles, often without producing symptoms. The infection, which is called toxoplasmosis , has been linked to mental illness, such as schizophrenia , and changes in behavior. The study's senior author Doctor Teodor Postolache, an associate professor of psychiatry  at the University of Maryland School of Medicine in the United States, said, "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 deserves additional studies." Doctor Albert Reece, vice president of medical affairs at the University of Maryland, said, "T. gondii infection is a major public health problem around the world, and many people don't realize they're infected. "Dr Postolache is a leading expert on suicide neuroimmunology . Suicide is a critically important mental health issue. About one million people commit suicide and another 10 million attempt suicide worldwide each year. We hope that this type of research will one day help us find ways to save many lives that now end too early in suicide." Dr. Postolache's research team at the University of Maryland was the first to report a connection between T. gondii and suicidal behavior in 2009. He is cooperating with researchers in Denmark, Germany and Sweden to confirm and investigate the way leading to this association. The T. gondii parasite thrives in the intestines of cats, and it is spread through their waste. All warm-blooded animals can become infected through contact with it. Humans can become infected by changing their infected cats' litter boxes, eating unwashed vegetables, drinking water from a polluted source, or by eating undercooked or raw meat. Not washing kitchen knives after preparing raw meat before handling another food item also can lead to infection. Pregnant women can pass the parasite directly to their unborn babies and are advised not to change cat litter boxes to avoid possible infection. Babies don't produce antibodies to T. gondii for three months after they are born, so the antibodies present in their blood represented infection in the mothers. The scientists studied Danish health patients to determine if any of these women later attempted suicide, including cases of violent suicide attempts which may have involved guns, sharp instruments and jumping from high places. 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. Dr Postolache noted limitations to the study, such as the inability to determine the cause of the suicidal behavior. The findings were published online in the Archives of General Psychiatry. The common way which is more likely to be infected with the disease is   _  .
to eat unwashed vegetables or undercooked meat to clean a place where a cat once lived for a time to pass the infection to her unborn baby during a woman's pregnancy to reuse kitchen tools which have been used to cut raw meat