title: A plea for symptom-based research in psychiatry.
abstract: BACKGROUND
  The significant proportion of patients suffering from subthreshold diagnoses such as partial posttraumatic stress disorder (PTSD) shows that today's diagnostic entities do not fully meet the reality and needs of clinical practice. Moreover, as stated also in the recently announced concept of research domain criteria (RDoC), the use of today's traditional diagnostic systems in psychiatric research does not sufficiently promote an integrative understanding of mental disorders across multiple units of analysis from behavior to neurobiology. Besides RDoC, core symptom-based research concepts have been proposed to bridge the translational gap in psychiatry, but, unfortunately, have not yet become the rule.
  
  
  OBJECTIVE
  First, this article briefly reviews literature on subthreshold PTSD (as an example for subthreshold diagnoses) and, second, pleas for and proposes a modified symptom-based research concept in psychiatry.
  
  
  RESULTS
  Subthreshold PTSD has, like other subthreshold psychiatric diagnoses, not yet been clearly defined. Diagnostic entities such as subthreshold PTSD are subject to a certain arbitrariness as they are mainly the result of empiricism. This fact stresses the urgent need for neurobiologically-informed psychiatric diagnoses and motivated the here-presented proposal of a symptom-based research concept. As proposed here, and before by other researchers, symptom-based research in psychiatry should refrain from studying patient cohorts compiled according to diagnoses but, instead, should focus on assessing cohorts grouped according to chief complaints or predominant psychopathological symptoms.
  
  
  CONCLUSIONS
  The linkage of the RDoC concept and symptom-based psychiatric research might probably speed up the definition of biologically or symptom-based psychiatric diagnoses, which might replace the auxiliary constructs of "traditional" diagnoses such as full and subthreshold PTSD, and promote the development of novel psychological and pharmacological treatments.
authors.affiliation: RG Molecular Psychotraumatology, Clinical Department, Max Planck Institute of Psychiatry, Munich, Germany; uschmidt@mpipsykl.mpg.de.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Schmidt
keywords: PTSD subtypes; PTSD subtyping; Posttraumatic stress disorder; RDoC; subclinical PTSD; subsyndromal PTSD; subthreshold PTSD; symptom-based research