Discovering that your cat isn't fond of you can be quite the depressing experience- but being bitten by your cat may be just the beginning of a very real depression. A recent study published to PLOS one has revealed a startling connection between cat bites and clinical depression. By combing through a large pool of data, researchers discovered that more than 41% of people treated for cat bites were also treated for depression at some point.
This surprising correlation raises several questions, especially considering that this percentage rises to 47% when the correlation between bites and depression is restricted to women. But what could explain this surprisingly strong relation and why is it that the correlation holds stronger for women than for men? The study’s methods reveal some insight- but they do believe that the cat bites have a causal relation to the cases of depression.
Explaining the Data
The research, led by Professors at University of Michigan and Virginia Tech, centered on this correlation confirmed its strength with these figures through rigorous research. Studying data from 1.3 million patients, to establish a causal link the researchers isolated 750 patients with cat bites and compared them to the 117,000 total patients that had been treated for depression. As expected, there were not a large percentage of cases of depression that had also been bitten by a cat; but, surprisingly, the number of cat bite victims that then suffered from depression was considerably high.
This one-sided relation can be contrasted against a similar comparison which explored the relation between depression and dog bites. The comparison acted as a proper control for the experiment, confirming that the link between cat bites and depression is significant. But when they considered the gender of the victim, they found that 85.5% of the patients who suffered from both cat bites and depression were female.
Researchers are considering three possibilities to explain their results. The first two cite depression as the cause of the correlation, stating that perhaps depressed people are more likely to be bitten. One reason for this increased likelihood is that depressed individuals are more likely to adopt a cat, and depressed women are more likely to do so than depressed men. The second possible factor is that depressed individuals are more likely to act in a way that facilitates biting.
Depression can cause hormonal shifts that may be noticeable to animals, including cats. Additionally, it can cause a loss of responsiveness and social cues that may elicit atypical behavior. The last hypothesis is that cats are infecting humans with a parasite when their bites puncture skin. The parasite Toxoplasma gondii is one proposed culprit for the infection and the resulting chemical changes that affect the victim.
A Parasitic Explanation
T. gondii is capable of spreading from cats to other mammals, including humans. Though it has been associated with depression, it also has been connected often to other mental disorders. Schizophrenia and obsessive compulsive disorder, for example, have both been linked to the parasite in humans. The parasite is capable of being passed through cat bites, although the researchers state that its typical behavior makes this explanation less likely to have been the cause of the results than the other two proposed causes.
Normally, the parasite is transmitted through contaminated food or drink or in utero from one generation of cat to the next. The parasite is also shed in the feces of cats, making litter boxes a possible area of contamination. This last explanation might link bites and depression through the related data point of the correlation between those who are bitten by cats and those that make contact with soiled kitty litter.
So although it’s not guaranteed that the bite itself is the cause of depression, the correlation between bites and depression is undeniable. Hopefully, this research will help guide further efforts to determine the true nature of this peculiar relation. If future experiments are able to isolate the cause for this correlation then they might also find a way to prevent depression. What do you think about the research and the link between depression and cat bites? Let us know in the comments section below!