Review supports infection link to schizophrenia
MedWire News: Results from a systematic review and meta-analysis of published studies support an association between certain infections and schizophrenia.
Previous studies have shown that schizophrenia has an important genetic component, as indicated by a high incidence of the disorder among patients' first degree relatives, explain Antonio Sorlozano (University of Granada, Spain) and colleagues.
However, the researchers say that "some authors suggest that schizophrenia might be caused, at least in a subgroup of patients, by congenital alterations which take place during neurodevelopment. These alterations could result from possible environmental factors, particularly infections."
But they add that previous studies on the association between infections and schizophrenia have produced conflicting results.
To review the evidence, the researchers searched the literature for relevant studies published up to December 2010 using the terms "schizophrenia," "viruses," "virus," "bacteria," "fungi," and "parasites."
In total, 56 case-control studies met criteria for inclusion in the meta-analysis.
Analysis of the pooled results revealed significant associations between schizophrenia and infection with human herpes virus 2 (11 studies), borna disease virus (23 studies), and human endogenous retrovirus W (four studies), at odds ratios (ORs) of 1.34, 2.03, and 19.31, respectively.
Regarding bacterial infections, the team found significant associations between schizophrenia and infection with Chlamydia pneumonia (four studies), Chlamydia psittaci (four studies), and Toxoplasma gondii (eight studies), at ORs of 6.34, 29.05, and 2.70, respectively.
However, the researchers note in the journal Schizophrenia Research that there was evidence for publication bias in the association between schizophrenia and T. Gondii infection.
Commenting on the findings, Sorlozano and colleagues say: "We recommend that new prospective and comparative studies, with sufficient sample power, should be undertaken to obtain more definite results. Such studies should use a combination of various microbiological techniques (simultaneously analysing blood, cerebrospinal fluid, and brain tissue using standardized techniques and with an adequate sensitivity) and take into account whether the patient is undergoing an acute bout or a stable phase of the disorder."
They add: "The possibility that there is an association between some microorganisms and the development of schizophrenia could provide means to improve both prevention and treatment."
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By Mark Cowen