Some cases of schizophrenia may be caused by this parasite

Schizophrenia affects more than 3 million people in the United States, according to the Schizophrenia and Related Disorders Alliance of America (SARDAA), and the majority of those cases can be attributed–at least partially–to genetics. No one knows the exact cause of this disorder, however, but new research suggests unexpected factors may come into play–such as parasitic infection.

For at least one-fifth of schizophrenia patients, infection may be exactly what is going on. According to research published in the journal Preventative Veterinary Medicine, the parasite Toxoplasma gondii (T. gondii), could be responsible for the brain changes associated with schizophrenia.

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T. gondii is known in the veterinary community as a parasite commonly found in cat feces, but T. gondii infection–also known as toxoplasmosis–typically occurs in people as a result of eating undercooked, contaminated meat or drinking contaminated water. It is a parasite commonly screen for in pregnant women, and as many as 60 million people in the United States may have the infection or have been exposed to it at one time.

In most people, T. gondii infection does not show any symptoms, but the Mayo Clinic indicates infants born to infected mothers and people with weakened immune systems can experience serious complications from the parasite. When T. gondii infection does develop symptoms, they typically mimic those related to the flu: body aches, swollen lymph nodes, headache, fever, and fatigue.

The exact cause-and-effect relationship between mental illness and T. gondii is not yet understood; however, studies have linked parasitic infection with brain damage in the past. It is possible such damage contributes to the symptoms of schizophrenia, but whether or not these symptoms are then complicated by an underlying genetic predisposition is not yet known.

In the research study, experts looked at countries with high levels of T. gondii infection. Those countries also had high rates of schizophrenia diagnosis. Using these numbers, the research team was able to calculate the population attributable fraction (PAF) number, or an estimated amount of cases that could be attributed to parasitic infection.

According to the data, as many as 21.4 percent of schizophrenia cases could be prevented by preventing T. gondii infection.

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“By finding out how important a factor T. gondii infection is, this work might inform our attitude to researching the subject,” said lead author Gary Smith, to MNT. “Instead of ridiculing the idea of a connection between T. gondii and schizophrenia because it seems so extraordinary, we can sit down and consider the evidence. Perhaps then we might be persuaded to look for more ways to reduce the number of people infected with toxoplasma.”

In 2012, T. gondii infection was linked to a 1.53 times higher risk of self-directed violent behavior among new mothers. That research, combined with this latest correlation, suggests the link between T. gondii infection and mental health is one that should be taken into consideration and researched more thoroughly.