title: Subtypes of panic attacks: a critical review of the empirical literature.
abstract: BACKGROUND
  Panic disorder is a heterogeneous disorder, comprising a variety of somatic, physiological, and cognitive symptoms during repeated panic attacks. As a result, considerable data have examined whether panic attacks may be classified into distinct diagnostic or functional subtypes. The aim of this study is to evaluate the existing literature regarding the validity of panic attack subtypes.
  
  
  METHODS
  This review focuses on data published since 2000, with the publication of DSM-IV-TR, augmented by replicated data published since 1980, with the publication of DSM-III and subsequently DSM-IV. Published reports evaluating empirical evidence for the validity of panic attack subtypes are reviewed.
  
  
  RESULTS
  Five sets of panic symptoms (respiratory, nocturnal, nonfearful, cognitive, and vestibular) have been shown to cluster together at varying degrees of consistency. However, none of these potential subtypes have been associated with sufficient and reliable external validation criteria indicative of functional differences. This apparent lack of findings may be related to methodological inconsistencies or limitations across the reviewed studies.
  
  
  CONCLUSIONS
  Although at present the data do not warrant the utility of subtyping, further research aimed at patent gaps in the literature, including clearer operationalization of symptom subtypes, greater use of biological challenge paradigms and physiological and other more objective measures of fear and anxiety, and exploration of subtyping based on biological factors such as genetics, may support the future designation of panic attack subtypes and their ultimate clinical utility.
authors.affiliation: Department of Psychology, University of California, Los Angeles, 1285 Franz Hall, Box 951563, Los Angeles, CA 90095-1563, USA. kkir@ucla.edu
authors.forename: Katharina
authors.initials: K
authors.lastname: Kircanski
authors.forename: Michelle G
authors.initials: MG
authors.lastname: Craske
authors.forename: Alyssa M
authors.initials: AM
authors.lastname: Epstein
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Wittchen
mesh_terms: D017668:Age of Onset; D001008:Anxiety Disorders / Q000145:classification / Q000175:diagnosis / Q000523:psychology; D001143:Arousal; D015897:Comorbidity; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005239:Fear; D020022:Genetic Predisposition to Disease; D006801:Humans; D016584:Panic Disorder / Q000145:classification / Q000175:diagnosis* / Q000235:genetics / Q000523:psychology; D013001:Somatoform Disorders / Q000145:classification / Q000175:diagnosis / Q000523:psychology