Infection can initiate symptoms of mental illness. It has been shown previously that Chlamydophila DNA is present six times more often in the blood of patients with schizophrenia than in the blood of control individuals. Monocytes, the main targets of Chlamydiaceae infection, are microglia precursors. We identified Chlamydiaceae infection using blinded brain DNA samples derived from the frontal cortex. Using PCR and sequence analysis, we found Chlamydophila DNA to be four times greater in patients with schizophrenia than in controls (schizophrenia: N=34, microbial DNA frequency 23.5%; controls: N=35, microbial DNA frequency 5.7%; P=0.045, OR=5.08). Persistent Chlamydophila-infected microglia or neuronal cells may impair neuronal circuits and thus be a mechanism for causing psychiatric illness in these patients.
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