An Article Claimed A Link Between Owning A Cat, Toxoplasmosis And Suicide – Is That True?

Ron Hines DVM PhD

No, I think the authors of that particular study drew the wrong conclusions from the data they collected.

The toxoplasmosis organism is one of the most common and successful parasites in the World. So it was quite likely that traces of its past presence would be found in human patients no matter what was being studied. (read here)

The authors of the more disturbing suicide study concluded that women with toxoplasma infections were 54% more likely to attempt suicide than those with no exposure to toxoplasmosis. They based that conclusion on the prevalence of antibodies to toxoplasma in these women’s newborn infants. (read here) Some have illogically extended that relationship to the ownership of cats in general. Some studies have even gone as far as to conclude that those who harbor a history of exposure to toxoplasma have more car crashes! (read here)

What none of these studies considered was that the psychological problems and the emotional stress that accompany depression and stress of all kinds significantly increase the risk of a toxoplasmosis relapse. It is called Stress recrudescense – a short term rise in antibodies against toxoplasmosis even without relapse. (read here) This same phenomena can occur in relapses of malaria, a close cousin protozoan parasite of toxoplasma. (read here) That is because of the chemical surges sudden emotional and physical stress often cause. (read here) We know that immunosuppressive drugs will reactivate toxoplasmosis as well. (read here) As a result, antibody levels against the parasite in the women studied would have been expected to rise. But I believe that the rise in toxoplasmosis antibody was the result of the stress – not the other way around as the authors mistakenly supposed.

So I think the authors of the study that linked toxoplasmosis antibody level to self-directed destructive behavior got it backwards – it was the stress that caused their antibodies against toxoplasmosis to rise, not the toxoplasmosis that caused the stress and self-directed trauma. I am not the only one to questions these conclusions drawn between toxoplasmosis and mental states. (read here)

There was another problem with these recent troubling studies; the authors also did not appreciate the common personality differences between cat and non-cat pet owners that veterinarians have learned to appreciate. Cat owners are thought to be more likely to direct stresses of all kinds inwardly. (read here)

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