An anonymous reader quotes a report from The Verge: Cats host a parasite called Toxoplasma gondii that other research has linked to various mental illnesses. So, for some time, people have wondered whether cats are unsafe; for example, pregnant women are usually told to stay away from litter boxes. (They should still do this because transmission during pregnancy is very real.) In a study published in the journal Psychological Medicine, researchers looked at data that tracked 5,000 Brits born in the early '90s until they were 18. This included information about whether the kids grew up with cats, or whether there were cats around when the mother was pregnant. After the scientists controlled for factors like socioeconomic status, there was no link between developing psychosis and having owned a cat. The researchers suggest that previous studies that did show a link had relatively small sample sizes. In addition, many of these studies asked people whether they remembered having cats, which is not quite as accurate. That said, it's important to keep in mind that some mental disorders linked to the parasite -- like schizophrenia -- tend to be diagnosed fairly late in life, so only tracking until age 18 might limit the study.