Neuropsychiatric disorders are difficult to diagnose because of phenotypic heterogeneity within and symptomatic overlap between disorders. This review describes how genomics and blood-based gene expression have shown potential as biomarkers for neuropsychiatric disorders (schizophrenia, bipolar disorder, and major depressive disorder) yet also discusses how a complex genetic landscape has limited sole genetic diagnostic tools for these disorders. In addition to their potential use as classifiers for neuropsychiatric disorders, genomic and blood-based biomarkers have revealed clues to the molecular pathways contributing to etiology. A comprehensive overview of studies to date has been given, and the authors provide suggestions for steps to be taken to ultimately move the laboratory-based classifiers towards application in a clinical setting. Furthermore, they share their vision for the future of these classifiers, both in clinical application and in opening up new ways to gain insights into the underlying biology.
Keywords: Neuropsychiatric disorders; bipolar disorder; blood-based gene expression; diagnostic classifiers; genomics; major depressive disorder; schizophrenia.