Investigating the living brain remains one of the major obstacles in psychiatry research in order to better understand the biological underpinning of brain disorders. Novel approaches are needed to study brain functions indirectly. Since it is part of the central nervous system, retinal functions as measured with the flash electroretinogram (ERG) may reflect the central dysfunctions reported in psychiatric disorders. This review describes the flash ERG anomalies reported in patients with psychiatric disorders such as seasonal affective disorder, schizophrenia, autism spectrum disorder and drug addiction and discusses how changes in retinal functions might be used as biomarkers for psychiatric disorder as well as a potential aid to diagnosis in psychiatry. (C) 2013 Elsevier Inc. All rights reserved.