No, it's not. The effect size that purportedly occurs according to this research (double-digit percentages of cases caused by toxo) would have been detectable o

No, it's not. The effect size that purportedly occurs according to this research (double-digit percentages of cases caused by toxo) would have been detectable on a population level. There would be marked differences in schizophrenia rates, but there aren't. You'd be right if small effect sizes were claimed, but that's not what's being claimed. Suppose a large portion of schizophrenia cases are caused by toxo. We know the toxo infection rate differs massively between countries, but the schizophrenia rate is consistent. Therefore, there must be another cause of schizophrenia such that its prevalence as a cause of schizophrenia is almost perfectly anti-correlated with toxo infections. More toxo infections, less of this other cause. Or there could be a correlated factor that prevents schizophrenia. Maybe having a cat, in and of itself, prevents schizophrenia. That seems extremely improbable, considering that a priori we should think that a particular amoeba causes schizophrenia is not probable.