Researchers have found a link between cat ownership and an increased incidence of schizophrenia-related disorders - Photo: Hepper
Researchers from Australia have found a link between cat ownership and schizophrenia after analyzing 17 studies published over the past 44 years from 11 countries, including the US and the UK.
Numerous studies have investigated the link between cats and schizophrenia.
Psychiatrist John McGrath and his colleagues, all from the Queensland Centre for Mental Health Research, explained: "We found a link between cat ownership and an increased incidence of schizophrenia-related disorders."
The idea that cat ownership might be linked to an increased risk of schizophrenia was suggested in a 1995 study, with exposure to a parasite called Toxoplasma gondii believed to be the cause.
But so far, research has yielded many different conclusions.
Studies have found that being close to cats during childhood may make a person more susceptible to schizophrenia. However, not all studies have found this link.
Some people also link exposure to cats to higher scores on scales measuring traits associated with schizophrenia, affecting thinking, feelings, and behavior, and psychotic-like experiences. Conversely, again, other studies have shown no link.
To get a clearer picture, McGrath and his team believe that a thorough review and analysis of all research on these topics is necessary. Toxoplasma gondii is a virtually harmless parasite that can be transmitted through undercooked meat or contaminated water.
Bites from infected cats or infected cat feces can also transmit Toxoplasma gondii .
An estimated 40 million people in the U.S. may be infected, often without any symptoms. Meanwhile, researchers continue to uncover more bizarre effects that the infection can have.
Once inside the human body, Toxoplasma gondii can invade the central nervous system and affect neurotransmitters. This parasite is associated with personality changes, the appearance of psychotic symptoms, and several neurological disorders, including schizophrenia.
More research is needed to draw a conclusion.
The research team stated: "After adjusting for covariates, we found that people who are exposed to cats have approximately double the risk of developing schizophrenia."
There are several important things to keep in mind here, such as the fact that 15 of the 17 studies were case-control studies. This type of study cannot prove cause and effect, and often fails to consider factors that may influence both exposure levels and outcomes. Some of the studies reviewed were of low quality, which the authors also highlighted.
A US study involving 354 psychology students found no link between cat ownership and schizophrenia scores. However, those who had been bitten by cats scored higher than those who had not.
Another study, which included people with and without mental disorders, found a link between cat bites and higher scores on tests measuring specific psychological experiences. But they suggested that other pathogens such as Pasteurella multocida could be an alternative cause.
Researchers agree that better and more extensive research is needed before any definitive explanation can be offered.
The authors wrote: "In summary, our review provides evidence supporting an association between cat ownership and schizophrenia-related disorders. More high-quality studies based on large representative samples are needed to better understand cat ownership as a potential risk modifier for psychotic disorders."
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