title: Neural structures, functioning and connectivity in Generalized Anxiety Disorder and interaction with neuroendocrine systems: a systematic review.
abstract: BACKGROUND
  Research on the neurobiological basis of Generalized Anxiety Disorder (GAD) has considerably expanded in recent years. However, many studies investigated different domains and used different methods and paradigms. Therefore, this review aims to integrate the findings to date and to identify the core correlates of neurobiological underpinnings of GAD discovered so far.
  
  
  METHODS
  We conducted a systematic review of original papers investigating neural correlates, connectivity, or structural changes as well as reporting changes in the serotonergic system, noradrenergic system and cortisol levels in DSM-IV-defined GAD samples until December 2013.
  
  
  RESULTS
  Studies have identified abnormal amygdala and prefrontal cortex activation in patients and decreased functional connectivity between these areas. Furthermore, studies showed increased gray matter volume and decreased structural connectivity between these structures. Neuroendocrine findings are less consistent, but increased reactivity of the noradrenergic system and perpetuations in the cortisol secretion have been reported.
  
  
  CONCLUSIONS
  Only studies on DSM-IV defined Generalized Anxiety Disorder which employed a group comparison were included.
  
  
  CONCLUSIONS
  Current research suggests a distinct set of neurobiological alterations in Generalized Anxiety Disorder. However, future research on the interaction between these structures and systems and on the specificity of these findings in relation to other mental disorders is urgently needed.
authors.affiliation: Institute of Clinical Psychology and Psychotherapy, Technische Universität Dresden, Dresden, Germany; Neuroimaging Center, Technische Universität Dresden, Dresden, Germany. Electronic address: Kevin.Hilbert@tu-dresden.de.
authors.forename: Kevin
authors.initials: K
authors.lastname: Hilbert
authors.affiliation: Institute of Clinical Psychology and Psychotherapy, Technische Universität Dresden, Dresden, Germany; Neuroimaging Center, Technische Universität Dresden, Dresden, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Lueken
authors.affiliation: Institute of Clinical Psychology and Psychotherapy, Technische Universität Dresden, Dresden, Germany; Neuroimaging Center, Technische Universität Dresden, Dresden, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Beesdo-Baum
mesh_terms: D000679:Amygdala / Q000503:physiopathology; D001008:Anxiety Disorders / Q000503:physiopathology*; D016022:Case-Control Studies; D039721:Diagnostic and Statistical Manual of Mental Disorders; D066128:Gray Matter / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D009490:Neurosecretory Systems / Q000503:physiopathology*; D009929:Organ Size; D017397:Prefrontal Cortex / Q000503:physiopathology
keywords: Anxiety disorder; Connectivity; Endocrinology; Generalized Anxiety Disorder; Neuroimaging; fMRI