Methods and biomarkers for diagnosing and monitoring psychotic disorders

A method of diagnosing or monitoring in a subject a psychotic disorder, a predisposition thereto, or monitoring efficacy of therapy thereof, comprising measuring, in a sample taken from the subject, the level of at least one first biomarker selected from (a) serotransferrin or a precursor thereof and (b) inter α-trypsin inhibitor, wherein the level of the biomarker is indicative of a psychotic disorder, a predisposition thereto, or the efficacy of therapy thereof, and wherein the indication of the psychotic disorder, or a predisposition thereto in the subject comprises a down-regulation of the level of serotransferrin or a precursor thereof, or inter α-trypsin inhibitor, or both, in the subject relative to a normal control.