TSPO and schizophrenia: In the present study, we aimed to compare TSPO expression between (i) schizophrenia patients with recent onset of symptoms (ROS group); (ii) an established illness group with at least 10 years of symptoms (ES group); and (iii) healthy controls using [11C](R)-PK11195 PET in order to determine differences across illness stages and to get a more conclusive answer regarding a potential role of microglial activation in schizophrenia.