Cat via Shutterstock
Everyone knows, or has heard of, the kooky old cat lady. And the stereotype is often thrown around as a mere punchline or low-grade insult. Yet while many see her as merely a joke, some publications have recently churned out headlines claiming she's no laughing matter.
The articles report, a bit fantastically like this one, that recent studies show that cats really do make people crazy. But let's get down to it, and take a closer look: Does owning a cat really lead to schizophrenia?
They cite a study published last June in the journal Schizophrenia Research (purchase required), which aimed to mimic the findings of past studies -- using a questionnaire -- to find a link between cat ownership in childhood, and schizophrenia in later life. It found that families with a child who later suffered severe mental illness were, in fact, more likely to have owned a cat than families without such future mental illness.
"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," the authors report in a press release that came out with the study's issue, according to CBS News.
Yet nowhere throughout the study do the authors claim that cats truly cause this disease.
"We urge our colleagues to try and replicate these findings," the authors write, "to clarify whether childhood cat ownership is truly a risk factor for later schizophrenia." It merely points to a correlation between the two, and leaves the question unanswered.
Past studies have come to similar -- albeit indefinite -- conclusions. A 1995 study focusing on a group of schizophrenics found that just over half had lived with a house cat in childhood, while just under 40 per cent of an unaffected group did. A similar study in 2000 had near-same results. Both, based on these findings, could only suggest a link. Yet none really claim that one causes the other.
So how likely is causation, really?
The Centers for Disease Control state that many cats carry the disease Toxoplasma, and that these cats may spread it to humans through their feces, which can contain the parasite, T. gondii, that causes the disease. Despite this, the question remains whether these cats' T. gondii can really lead to schizophrenia in humans. No studies as yet have found evidence. The CDC notes that, while largely genetic in origin, schizophrenia may be sped up by such diseases as T. gondii in those with the right genes, but that's not proven as well.
The authors note that both T. gondii and schizophrenia have their roots in early life. "The ability of Toxoplasma organisms to infect the perinatal brain is thus consistent with this aspect of schizophrenia pathogenesis," they wrote.
And studies also point to the fact that T. gondii and schizophrenia both affect the same parts of the brain. Two past studies found that both altered astrocytes in the brain, while other studies show that both affect dopamine, norepinephrine and neurotransmitter levels.
Still, one must ask: if cat ownership really does increase the risk of mental illness, why aren't there many more people with schizophrenia? The CDC says that only 1 percent of people in the U.S. and Europe suffer from schizophrenia, yet the Humane Society claims there are between 75 and 80 million pet cats in homes (and another 30 to 40 million stray cats) in the country.
All in all, the numbers simply don't add up for such a link to hold true.