Cats may rule the Internet and make beloved pets, but a recent study has revealed that they may also be linked to mental illness.

As cute as they can be, cats can carry a parasite called Toxoplasma gondii (T. gondii), which can be passed on to humans. The Centers for Disease Control and Prevention (CDC) estimates more than 60 million people in the U.S. may have it, CBS reports. Though most people will never develop symptoms of a T. gondii infection, those with weakened immune symptoms could develop an illness called toxoplasmosis, which could lead to miscarriages, fetal development disorders, a flu-like illness, blindness and in extreme cases even death. Recently published research now suggests that there could be a link between the cat-carried parasite and mental illness.

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The researchers, E. Fuller Torrey of the Stanley Medical Research Institute and Dr. Robert H. Yolken of Stanley Laboratory of Developmental Neurovirology at the Johns Hopkins University School of Medicine, have been investigating a possible link between the parasite and mental illnesses such as schizophrenia and bipolar disorder. The new research, published in Schizophrenia Research, examines whether cat ownership in childhood is significantly more common in families in which the child later becomes seriously mentally ill.

“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 of the study said in a statement.

Another recent study, published in the journal Acta Psychiatrica Scandinavica, looked at dozens of published studies that also found that T. gondii infection is associated with mental disorders. The results of the research showed that a person infected with the parasite was almost twice as likely to develop schizophrenia.

So what can cat-loving parents do? Study author Torrey told CBS that, “Children can be protected by keeping their cat exclusively indoors and always covering the sandbox when not in use.”

Read next: Man Calls 911 Because His Cat Locked Him Out of the House for Four Hours

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