The suspected culprit is a parasite called Toxoplasma gondii. It can lead to toxoplasmosis, a disease that may cause flu-like symptoms in some people but most people who contract it won't develop signs or symptoms. Most people don't show any symptoms of the infection, but people with a weaker immune system could get sick with toxoplasmosis, which has been linked to miscarriage, fetal developmental disorders, blindness, and flu-like symptoms. However, they ultimately learned that these problems were actually caused by other factors than the animal. But people can also become infected with T. gondii from undercooked meat or contaminated water.
The new study did not directly measure T. gondii exposure, but the researchers say their results suggest that if the parasite does cause psychiatric problems, their study suggests that cat ownership doesn't significantly increase the risk of exposure to the parasite. New British research challenges earlier beliefs that mental health was at risk.
The research team studied almost 5,000 participants, who were all born in 1991 or 1992, until the age of 18. "Our findings should reassure people that owning a cat in pregnancy or childhood is not related to later risk of psychotic symptoms". At ages 13 and 18 years, the children were brought into clinics to be evaluated for psychotic-like symptoms. This is the first study to take a look at childhood cat ownership and infection of the said parasite as a factor in pyschosis. Turns out those reports that people who grew up with cats have a higher risk of mental illness are not true. That link led researchers to believe raising children in a household with cats could lead to later development of mental illness. Pregnant women should still follow healthy guidelines from their doctor when it comes to dealing with such things as soiled kitty litter, but in general having a cat does not increase the likelihood of mental health problems.
Dr. James Kirkbride, also with UCL Psychiatry and author on the study, says, "There is good evidence that T. gondii exposure during pregnancy can lead to serious birth defects and other health problems in children".
However, a new study published in the journal, Psychological Medicine, suggests that owning a cat during in pregnancy and childhood does not play a role in developing psychotic symptoms during adolescence.
The Canadian Centre for Occupational Health and Safety (CCOHS) lists several occupations that may be at risk for contracting the parasite.