"Does Toxoplasmosis Cause Schizophrenia?"
The brain parasite toxoplasma infects about one-third of the population
of developed countries—about one in four adults in the U.S.
But the life-long presence of dormant stages of this parasite
in the brain and muscles of infected humans is usually considered
asymptomatic from a clinical point of view.
There’s like this “dynamic interplay between the parasite,
[the human brain], and [our] immune response that results
in this detente that promotes the life-long
persistence of the parasite in our brains.”
We can’t get rid of it, but at least we can keep it from killing us,
unless we get AIDS or something and our immune defenses drop.
“Within the past 10 years, however, many independent studies
have shown that this parasitic disease…
could be indirectly responsible for hundreds of thousands of deaths
due to its effects on the rate of traffic and workplace accidents,
and also suicides.
Moreover, [this] latent toxoplasmosis is probably
one of the most important risk factors for schizophrenia.”
Schizophrenia does have a strong genetic component,
but even if you have the exact same genes as a schizophrenic—
your identical twin has schizophrenia—
the chances of you having it are still
probably less than 50 percent.
So what else might increase risk?
Studies performed over five decades in 20 countries
found toxoplasma infection nearly triples the odds of schizophrenia.
That’s more than any so-called schizophrenia
gene that has been described so far.
Now obviously, everyone who gets this parasite in their brain
does not come down with schizophrenia.
It may depend on where exactly in the brain
the parasite ends up taking up residence,
but this increased prevalence of toxoplasma in schizophrenics
has been demonstrated by at least 50 published studies.
Yeah, but what about studies that weren’t published—
maybe the ones that found no connection were just shelved or something.
Even accounting for this so-called publication bias,
“the evidence of an association with [toxoplasma seems] overwhelming."
Yeah, but it’s still just an association.
Instead of “toxo” causing schizophrenia,
maybe schizophrenia causes toxo...
For example, institutionalized psychiatric patients may be fed undercooked meat,
thereby increasing their exposure to toxoplasma infection.
That’s where the military studies come in.
The U.S. military routinely collects and stores blood of its service members.
This affords a unique opportunity to check people
for infection well before the diagnosis of disease,
so you can see which came first.
And it was the toxo.
The infection can be found prior to the onset of psychotic symptoms.
“The strongest evidence for [a cause-and-effect] role of toxoplasma
in triggering schizophrenia comes from a recent MRI study,
showing that differences in brain [structure,]
originally thought to be characteristic of schizophrenia patients…
[were] actually present only in [those infected with the parasite.]”
See—there are these gray matter anomalies more often found
in schizophrenia patients, but when you split them up
into those testing positive and negative for toxo,
you only really see it in the infected brains.
So, does that mean we might be able to treat schizophrenia
with antiparasitic drugs?
Well, there is this tetracycline-type drug that can kill off toxoplasma
in mice, and when given to schizophrenics
does seem to improve symptoms,
but the drug may also have independent anti-inflammatory
and neuroprotective properties;
so, we don’t know if it was a toxo effect.
“Future research should look to delineate the antiparasitic effect
of minocycline…” by testing the patients for toxo
to see if the drugs work better in those that have been infected.
There have been four randomized controlled trials
specifically evaluating antiparasitic drugs in patients
with schizophrenia and… no effect was found.
But, incredibly, not a single one of those studies used a drug
that has been shown to actively kill off the parasites,
once they’ve been walled off in the brain.
See—"after acute infection, the parasites form these cysts
in the brain, leading to lifelong chronic infection
and drug resistance to commonly used antiparasitics.”
“There are currently no ongoing trials of anti-toxoplasma therapy
in schizophrenia despite ample evidence to justify further testing.”
I hope some researcher listening to this will realize
the time is ripe to evaluate antiparasitic drugs
in toxo-infected patients with this horrible disease.