By Bob Carolla, NAMI Director of Media Relations
First, let me say that I like cats.
A friend of mine is a former director of a Humane Society chapter in Kansas. A radio station disc jockey once asked to interview her for National Cat Day. Her first response was to warn sternly, “You had better not make fun of cats.”
Cats sometimes are the subject of mischievous, satirical, mocking or even sick humor. Over the years, cartoon cats have included Bill the Cat (Bloom County), Bucky (Get Fuzzy), the Cat in the Hat, Felix the Cat, Garfield, Heathcliff, Scratchy (The Simpsons) and Sylvester in Looney Tunes (pardon the term).
All of which may be why some people snicker when I mention a recent study on the relationship between cat bites and depression. Others don’t believe me and rise to feline defense. After all, most studies have generally found mental health benefits in pet ownership.
Skepticism may be warranted, but the humor is misplaced. It’s a serious study, especially when considered relative to previous research about a possible connection between cats and schizophrenia.
The University of Michigan study found that approximately 40 percent of people bitten by cats develop depression at some point—five times more likely than for people who aren’t bit. By comparison, the overall rate of depression in the general population is 5 to 8 percent.
In the study, the proportion of women who developed depression after a cat bite was twice the number of men, 47 percent vs. 24 percent. Interestingly, that proportion is identical to that of women to men with depression in the general population.
Dog bites were also considered as part of the study. The possibility of developing depression after being bit by a dog is lower, but still significant at 29 percent.
It is important to note that the findings do not imply causation. They only make a case for “further investigation.” However, the study argues that “targeted screening” for depression would be a prudent safeguard now for anyone who sees a clinician for an “acute injury from a household pet.”
One problem with that proposal is other research cited in the study has shown that only 40 percent of people bitten by cats seek medical care. I also can’t help but wonder about timing. Would onset of symptoms of depression really be evident within 24 to 48 hours of an “acute bite”—the period in which a person who’s been bitten might seek care?
The study also found that people who become infected by toxoplasma gondi (T.gondi), a parasite sometimes found in cats, are seven times more likely to die from suicide. However, cat bites are not associated with T.gondi. It is a separate risk.
The study was conducted through computerized “data mining,” applying search words to more than one million electronic health records over a 10-year period. Closer examination produced 117,000 reports of depression, 1,100 dog bites and 750 cat bites. The correlation of bites to depression was highest for cats. Cat scratches were not considered bites.
Although the study suggests that depression follows cat bites, an alternative, converse theory might be that cats simply tend to bite people living with depression more often than other people. In other words, the bites follow depression—or as one friend speculated, cats are “telepathic” and more prone to be ornery around a person living with depression. That’s not very likely in my mind; however, the Michigan study cites a different study of “personality types” that suggests “cat people” have a higher level of “neuroticism” than “dog people,” which would mean a higher risk of depression. The personality of individual cats might similarly be a concern.
Results also may be skewed if people living with depression are more likely than others to seek medical care for cat bites. In households with multiple pets, bites may also be incurred from breaking up fights between the various animals. The fights themselves might be a source of anxiety, leading to depression.
While the Michigan study is the first to explore a possible relationship between cats and depression, much research has explored possible connections between T.gondi and schizophrenia. The research was summarized succinctly two years ago in The Atlantic.
The leading figure in the research, Dr. E. Fuller Torrey has recommended that pregnant women not clean litter boxes, that parents not buy cats for young children and to make sure sandboxes are covered to prevent cats from using them as litter boxes. Schizophrenia.com also has published a comprehensive list of preventive precautions in another summary of T.gondi research.
The University of Michigan study has a wealth of fascinating data and discussion. For example, the electronic records that were scrutinized also contained reports of squirrel, bat, raccoon, mole, monkey, mouse, parrot, pig, snake, lizard, piranha and prairie dog bites.
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