Bad news for cat lovers. A new study published in the journal Schizophrenia Research indicates a possible link between childhood cat ownership and increased risks of developing schizophrenia and other mental illnesses later in life.

The threat lies in the cats' feces. Cats may carry a parasite known as Toxoplasma gondii, which is shed when they defecate. Cat lovers are at risk if they come in contact with feces, such as when cleaning litter boxes. To be fair to the kitties, the parasite is also found in undercooked meats and unwashed fruits and vegetables. But because so many in the U.S. own cats (around 35 percent of households, according to the ASPCA), feline fecal matter is quite prevalent.

Researchers from the Stanley Medical Research Institute, a non-profit organization that specializes in the treatment of schizophrenia and bipolar disorders, reviewed two previous studies linking childhood cat ownership to increased risk of mental illness. They reproduced the studies using a questionnaire developed by the National Alliance for the Mentally Ill (NAMI) and their results matched those of the previous studies.

"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," lead authors say.

One of those studies was conducted by researchers at the Academic Medical Centre in Amsterdam, which found that individuals infected with T. gondii were twice as likely to develop schizophrenia as those not infected.

Most people who have toxoplasmosis are unaware they are infected. The condition can present with flu-like symptoms, such as muscle pain and swollen lymph glands. Severe toxoplasmosis can damage the brain, eyes, and other internal organs. The condition is especially dangerous for those with compromised immune systems or pregnant women who are newly infected, since they risk passing it on to their newborns.

"I don't want to cause any panic," says Joanne Webster, a parsitologist at the Imperial College London who has studied the parasite. "In the vast majority of people, there will be no ill effects, and those who are affected will mostly demonstrate subtle shifts of behavior. But in a small number of cases, [Toxo infection] may be linked to schizophrenia and other disturbances associated with altered dopamine levels -- for example, obsessive-compulsive disorder, attention-deficit hyperactivity disorder, and mood disorders."

If you feel you may be at risk, toxoplasmosis can be diagnosed with a simple blood test. In the meantime, take care with that litter box and be sure to wash your hands.