Cytokine function in medication-naive first episode psychosis: A systematic review and meta-analysis.

This systematic review sets out to give a comprehensive overview of the
cytokine profile at the onset of psychosis un-confounded by medication.
We aim to provide insight into the early pathophysiological process of
psychosis and areas for future research of potential biomarkers able to
chart the extent of illness or effectiveness of treatment. Following
PRISMA guidelines, a systematic primary search identified 4638
citations, 4651 studies were retrieved and screened, and 23 studies met
the inclusion criteria (published in English before June 2013, patients
with neuroleptic naive first episode psychosis, and assessed circulating
cytokines). These reported 570 patients, 683 healthy control subjects,
and 20 cytokine/cytokine receptors. Papers that contained sufficient
stratified data were included in a random-effects pooled effect size
meta-analysis. Highly significant effect sizes were found for elevated
IL-1β, sIL-2r, IL-6, and TNF-α. Non-significant effect size estimates
were obtained for IL-2, IL-4, and IFN-γ. Thus, we found significant
elevation in pro-inflammatory cytokine levels in the serum of patients
with medication-naive first episode psychosis. This adds to the evidence
of a pro-inflammatory immune deregulation in schizophrenia and suggests
these cytokines should be the focus for further research in biomarkers
of progress and extent of illness. Future studies should focus on the
medication-naive group at the early stages of illness with numbers large
enough to allow for the control of other potential confounding factors.

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