Q. I've read about Dr. E. F. Torrey's hypothesis about toxoplasma gondii and mental illness. I have two sons (22 and 25) with bipolar disorder. Does it make any sense to get them tested for antibodies to this parasite? Has there been any research testing the effects of treatment for toxoplasmosis on bipolar patients?

A. The short answer, in my estimation, is probably not--unless your sons are showing the other clinical evidence of toxoplasma (T. gondii) infection. As you may know, T. gondii is a microscopic parasite thought to be contracted by eating undercooked meat or contaminated soil. It may also be contracted by handling infected kitty litter, since cats are the definitive host of this parasite.

Dr. Torrey has been at the fore-front of research into possible infectious causes of mental illness. But despite the many tantalizing correlations and associations that have been found over the past 20 years, it remains to be proven that major mental illnesses, such as schizophrenia or bipolar disorder, are caused by infectious or parasitic agents. Of course, symptoms that mimic those of major mental illness may well appear in the course of infectious processes.

That said, there are suggestive studies linking T. gondii exposure with some psychiatric illnesses (for a review, see Hinze-Selch D, Bipolar Disord 2002;4 Suppl 1:81-3). For example, Yolken et al (Clin Infect Dis 2001 Mar 1;32(5):842-4) found that individuals with first-episode schizophrenia had significantly increased levels of IgG, IgM, and IgA class antibodies to Toxoplasma proteins, as compared with the control subjects. However, there is evidence that in the U.S., as many as 30% of individuals aged 10-19 years show evidence of exposure to T. gondii--a much higher prevalence than schizophrenia and bipolar disorder combined.

So--it's not clear how specific evidence of T. gondii exposure is, with respect to psychiatric disorders. It is true that when T. gondii gets into the brain, it can cause neuropsychiatric symptoms, such as encephalitis; but this should be evident in the clinical picture and in radio-imaging studies, such as a CAT scan or MRI of the brain.

I think one could make an argument for getting such imaging studies in any patient who first presents with a major psychiatric disorder, since there are numerous brain diseases that can mimic schizophrenia or bipolar disorder; for example, multiple sclerosis affecting the brain.

I don't want to discourage you from getting a thorough medical evaluation of your sons. I advise that for all individuals first presenting with a major psychiatric disorder. But I think T. gondii is a long-shot when it comes to the cause of bipolar disorder.

August 2003

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