(CNN) Studies have suggested that cat ownership could be linked to certain mental disorders, such as schizophrenia, but researchers at University College London say they found no link between cat ownership and the development of psychotic symptoms. 
 
 Published in the medical journal Psychological Medicine , the new study is the first to prospectively look at childhood cat ownership and the infection of the parasite Toxoplasma gondii as a risk factor for psychosis. 
 
 House cats are known to be the primary host of T. gondii, which infects various warm-blooded animals (including humans) and causes a disease called toxoplasmosis 
 
 According to the US Centers for Disease Control and Prevention, more than 60 million people in the United States may be infected with the parasite. However, most individuals who develop toxoplasmosis experience few symptoms because their immune systems keep the parasite from causing illness. 
 
 But in pregnant women and those with compromised immune systems, the disease could cause serious health problems, including damage to the brain, eyes and other organs. Infants who are born to women infected with T. gondii during or just before their pregnancy are most at risk for developing severe toxoplasmosis. 
 
 Toxoplasmosis can be contracted through undercooked meat and contaminated water, but it can also be contracted through contact with feces containing the parasite. 
 
 Previous research into cat ownership and the development of mental health disorders has been limited, according to Francesca Solmi, the lead author of the study and a research associate in the Division of Psychiatry at University College London. 
 
 "Because cats are the primary host of Toxoplasma gondii, it had been suggested that they might put people at increased risk of mental illness, including schizophrenia, by exposing them to T. gondii infection," she said. "However, some of the studies that have looked at this association had methodologically limitations." 
 
 These limitations included studies in which researchers asked people with and without mental health problems to remember details about their childhood, which could have led to errors in recall. 
 
 The new study looked at nearly 5,000 people in the United Kingdom who were born between 1991 and 1992 and followed them until the age of 18. The researchers used birth information to determine whether households had cats when the mothers were pregnant and when the children were growing up. At ages 13 and 18 years, the children were brought into clinics to be evaluated for psychotic-like symptoms. 
 
 After controlling for potential confounding factors, the study concluded that cat ownership in pregnancy and childhood did not play a role in developing psychotic symptoms during adolescence. 
 
 "The message for cat owners is clear: there is no evidence that cats pose a risk to children's mental health," Solmi said in a news release. "In our study, initial unadjusted analyses suggested a small link between cat ownership and psychotic symptoms at age 13, but this turned out to be due to other factors." 
 
 She added, "Once we controlled for factors such as household over-crowding and socioeconomic status, the data showed that cats were not to blame. Previous studies reporting links between cat ownership and psychosis simply failed to adequately control for other possible explanations." 
 
 Although the study did not measure T. gondii exposure directly, the results do suggest that if the parasite causes psychiatric problems, cat ownership does not significantly increase exposure. 
 
 However, other experts believe that adjusting for other possible explanations may eliminate the cause of the exposure itself. "By itself, household crowding is a risk factor that has been associated with schizophrenia, and if the crowding leads to greater contact with the household cats, then adjusting for household crowding statistically may eliminate the legitimate association between cat exposure and, in this case, unusual thoughts," said Dr. E. Fuller Torrey, an associate director of research at the Stanley Medical Institute who has also conducted research in cat ownership and toxoplasmosis. 
 
 The researchers continue to recommend that pregnant women handle cat litter with caution. 
 
 "There is good evidence that T. Gondii exposure during pregnancy can lead to serious birth defects and other health problems in children. As such, we recommend that pregnant women should continue to follow advice not to handle soiled cat litter in case it contains T. Gondii," senior study author James Kirkbride of University College London said in a news release. 
 
 Soiled litter boxes are not the only places to contract the parasite. "You don't have to own a cat to be exposed to contaminated feces," Fuller said. "For example, cats love sandboxes because of the loose soil." He warns that any loose soil can easily be contaminated by neighborhood cats. 
 
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 Solmi says she is relieved at the results of her study. "Many people own cats, and it's reassuring that our findings suggest that cat ownership is not associated with an increased risk of mental illness, as previously suggested." 
 
 She suggests that future studies look at replicating this research study to add more evidence. ||||| Over the past few years, cats have increasingly attracted media attention due to a number of scientific studies reporting that a Toxoplasma Gondii (T. Gondii) infection is linked with mental health issues, including schizophrenia, suicide and intermittent rage disorder. Since domestic cats are the primary hosts of T. Gondii – that is, they provide an environment within which this parasite can reproduce – it is often speculated that cat ownership may put people at increased risk of mental illness, by exposing them to it. 
 
 However, only a handful of small studies have found evidence to support a link between owning a cat and psychotic disorders, such as schizophrenia. And most of these investigations have serious limitations. For instance, they relied on small samples, did not specify how participants were selected, and did not appropriately account for the presence of missing data and alternative explanations. This can often lead to results that are born out of chance or are biased. 
 
 To tackle these limitations, we conducted a study using data from approximately 5,000 children who took part in the Avon Longitudinal Study of Parents and Children between 1991 and 1992. Since then, these children and their families have been followed up to gather information on their health, as well as on their demographic, social and economic circumstances. 
 
 So, unlike previous studies, we were able to follow people over time, from birth to late adolescence, and address a number of the limitations of previous research, including controlling for alternative explanations (such as income, occupation, ethnicity, other pet ownership and over-crowding) and taking into account missing data. 
 
 We studied whether mothers who owned a cat while pregnant; when the child was four years old; and 10 years old, were more likely to have children who reported psychotic symptoms, such as paranoia or hallucinations, at age 13 and 18 years of age. Although most people who experience psychotic symptoms in adolescence will not develop psychotic disorders later in life, these symptoms often indicate an increased risk for such disorders and other mental illnesses, including depression. 
 
 So are cats bad for your mental health? Probably, not. 
 
 We found that children who were born and raised in households that included cats at any time period – that is, pregnancy, early and late childhood – were not at a higher risk of having psychotic symptoms when they were 13 or 18 years old. This finding in a large, representative sample did not change when we used statistical techniques to account for missing data and alternative explanations. This means that it is unlikely that our results are explained by chance or are biased. 
 
 While this finding is reassuring, there is evidence linking exposure to T. Gondii in pregnancy to a risk of miscarriage and stillbirth, or health problems in the baby. In our study, we could not directly measure exposure to T. Gondii, so we recommend that pregnant women should continue to avoid handling soiled cat litter and other sources of T. Gondii infection, such as raw or undercooked meats, or unwashed fruit and vegetables. That said, data from our study suggests that owning a cat during pregnancy or in early childhood does not pose a direct risk for offspring having psychotic symptoms later in life. ||||| Angold , A , Costello , EJ , Messer , SC , Pickles , A , Winder , F , Silver , D ( 1995 ). Development of a short questionnaire for use in epidemiological studies of depression in children and adolescents . International Journal of Methods in Psychiatric Research 5 , 237 – 249 . 
 
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 New UCL research has found no link between cat ownership and psychotic symptoms, casting doubt on previous suggestions that people who grew up with cats are at higher risk of mental illness. 
 
 Recent research has suggested that cat ownership might contribute to some mental disorders, because cats are the primary host of the common parasite Toxoplasma Gondii (T. Gondii), itself linked to mental health problems such as schizophrenia. However, the new study, published in Psychological Medicine, suggests that cat ownership in pregnancy and childhood does not play a role in developing psychotic symptoms during adolescence. The study looked at nearly 5000 people born in 1991 or 1992 who were followed-up until the age of 18. The researchers had data on whether the household had cats while the mother was pregnant and when the children were growing up. 
 
 "The message for cat owners is clear: there is no evidence that cats pose a risk to children's mental health," says lead author Dr Francesca Solmi (UCL Psychiatry). "In our study, initial unadjusted analyses suggested a small link between cat ownership and psychotic symptoms at age 13, but this turned out to be due to other factors. Once we controlled for factors such as household over-crowding and socioeconomic status, the data showed that cats were not to blame. Previous studies reporting links between cat ownership and psychosis simply failed to adequately control for other possible explanations." 
 
 The new study was significantly more reliable than previous research in this area since the team looked at families who were followed up regularly for almost 20 years. This is much more reliable than methods used in previous studies, which asked people with and without mental health problems to remember details about their childhood. Such accounts are more vulnerable to errors in recall which can lead to spurious findings. 
 
 Previous studies were also relatively small and had significant gaps in the data, whereas the new study looked at a large population and was able to account for missing data. The new study was not able to measure T. Gondii exposure directly, but the results suggest that if the parasite does cause psychiatric problems then cat ownership does not significantly increase exposure. 
 
 "Our study suggests that cat ownership during pregnancy or in early childhood does not pose a direct risk for later psychotic symptoms," explains senior author Dr James Kirkbride (UCL Psychiatry). "However, there is good evidence that T. Gondii exposure during pregnancy can lead to serious birth defects and other health problems in children. As such, we recommend that pregnant women should continue to follow advice not to handle soiled cat litter in case it contains T. Gondii." 
 
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– New research is sure to get cat owners purring: Despite suggestions that cats may boost one's risk of psychiatric disorders and other mental illnesses, a new study finds people who grow up in a house with cats are no more likely to suffer from mental illness than those who steer clear of cats. "The message for cat owners is clear: There is no evidence that cats pose a risk to children's mental health," the lead author says in a release. While it doesn't dispute the link between mental illness and a parasite carried in cat feces, known as Toxoplasma gondii, the Psychological Medicine study does suggest previous studies linking cat ownership and psychosis failed to consider factors like household over-crowding and socioeconomic status. Researchers followed 5,000 children from birth to age 18, gathering health data as well as information on whether they grew up with a cat or even whether their mother lived with a cat while pregnant, per the Conversation. Though they couldn't measure T. Gondii exposure directly, they found cat ownership in pregnancy and childhood did not increase one's risk of psychiatric problems, per CNN. Researchers did find "a small link between cat ownership and psychotic symptoms at age 13, but this turned out to be due to other factors," the author says. Researchers maintain, however, that T. Gondii exposure during pregnancy can lead to miscarriage, stillbirth, and other health problems for the baby so pregnant women shouldn't handle soiled cat litter. (This study shows how to cheer a grumpy cat.)