Professor Stephen Lawrie, Professor of Psychiatry and Head of the Division of Psychiatry at the University of Edinburgh, delivers his Medical Detectives lecture entitled "Scanning for a Diagnostic Test for Schizophrenia". Brain imaging can be used to distinguish patients with schizophrenia from their relatives, and from other patients with major psychiatric disorders such as bipolar disorder and autism. This talk takes a journey through these investigations, lay out the evidence and show how outcomes may be enhanced and possibly even prevent psychosis in high risk populations. Recorded on 24 October 2013 at The University of Edinburgh's Anatomy Lecture Theatre.