A scoping review of protein biomarkers for schizophrenia: State of progress, underlying biology, and methodological...

Schizophrenia is characterized by symptoms such as delusions, hallucinations, and avolition. The diagnosis is clinical, based on interviews and the main treatment involves antipsychotics. Currently, given the lack of clinically applicable biomarkers for schizophrenia, there is no molecular test based on its biological mechanisms to assist psychiatrists either in the prediction or diagnosis of the disorder, nor to measure medication efficacy. This scoping review assessed original articles in English about protein biomarkers for schizophrenia with samples that could be used in a clinical context, classifying them into diagnosis, prognosis, therapeutics, risk for psychosis, and side-effects. The search was conducted on PubMed and key findings were inserted on a summary table. We discussed the methodologies used in these papers, suggested protein panels for validation in longitudinal research, and proposed a hypothesis to explain the observed variability in results. This heterogeneity is explored in light of the debated validity of this construct, applying recent discussions and the disorder's history. Our data suggest that there is insufficient evidence to integrate protein biomarkers into clinical psychiatry for schizophrenia, not due to study quality, but possibly due to flaws in the current diagnostic system. We propose exploring alternative categorization systems.