Owning a cat as a kid could put you at risk for schizophrenia and bipolar disorder later on because of parasites found in feline feces, new research says.

Previous studies have linked the parasite toxoplasma gondii (T. gondii) to the development of mental disorders, and two more research papers published recently provide further evidence.

Researchers from the Academic Medical Centre in Amsterdam looked at more than 50 studies and found that a person infected with the parasite is nearly twice as likely to develop schizophrenia.

The other study, led by Dr. Robert H. Yolken of Johns Hopkins University School of Medicine in Baltimore, confirmed the results of a 1982 questionnaire that found half of people who had a cat as a kid were diagnosed with mental illnesses later in life compared to 42% of those who didn't grow up with a cat.

"Cat ownership in childhood has now been reported in three studies to be significantly more common in families in which the child is later diagnosed with schizophrenia or another serious mental illness," the authors said in a press release.

The findings were published in Schizophrenia Research and Acta Psychiatrica Scandinavica.

T. gondii, which causes the disease toxoplasma, is especially risky for pregnant women and people with weak immune symptoms. The parasite can also be found in undercooked meat and unwashed fruits and vegetables.