title: Psilocybin-Induced Decrease in Amygdala Reactivity Correlates with Enhanced Positive Mood in Healthy Volunteers.
abstract: BACKGROUND
  The amygdala is a key structure in serotonergic emotion-processing circuits. In healthy volunteers, acute administration of the serotonin 1A/2A/2C receptor agonist psilocybin reduces neural responses to negative stimuli and induces mood changes toward positive states. However, it is little-known whether psilocybin reduces amygdala reactivity to negative stimuli and whether any change in amygdala reactivity is related to mood change.
  
  
  METHODS
  This study assessed the effects of acute administration of the hallucinogen psilocybin (.16 mg/kg) versus placebo on amygdala reactivity to negative stimuli in 25 healthy volunteers using blood oxygen level-dependent functional magnetic resonance imaging. Mood changes were assessed using the Positive and Negative Affect Schedule and the state portion of the State-Trait Anxiety Inventory. A double-blind, randomized, cross-over design was used with volunteers counterbalanced to receive psilocybin and placebo in two separate sessions at least 14 days apart.
  
  
  RESULTS
  Amygdala reactivity to negative and neutral stimuli was lower after psilocybin administration than after placebo administration. The psilocybin-induced attenuation of right amygdala reactivity in response to negative stimuli was related to the psilocybin-induced increase in positive mood state.
  
  
  CONCLUSIONS
  These results demonstrate that acute treatment with psilocybin decreased amygdala reactivity during emotion processing and that this was associated with an increase of positive mood in healthy volunteers. These findings may be relevant to the normalization of amygdala hyperactivity and negative mood states in patients with major depression.
authors.affiliation: Department of Psychiatry, Psychotherapy and Psychosomatics, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland; Department of Neuropsychopharmacology and Brain Imaging, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland. Electronic address: r.kraehenmann@bli.uzh.ch.
authors.forename: Rainer
authors.initials: R
authors.lastname: Kraehenmann
authors.affiliation: Department of Neuropsychopharmacology and Brain Imaging, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland.
authors.forename: Katrin H
authors.initials: KH
authors.lastname: Preller
authors.affiliation: Department of Psychiatry, Psychotherapy and Psychosomatics, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland; Department of Neuropsychopharmacology and Brain Imaging, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland; Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich; and Institute for Biomedical Engineering, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland.
authors.forename: Milan
authors.initials: M
authors.lastname: Scheidegger
authors.affiliation: Department of Neuropsychopharmacology and Brain Imaging, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pokorny
authors.affiliation: Department of Psychiatry, Psychotherapy and Psychosomatics, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland.
authors.forename: Oliver G
authors.initials: OG
authors.lastname: Bosch
authors.affiliation: Department of Psychiatry, Psychotherapy and Psychosomatics, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland.
authors.forename: Erich
authors.initials: E
authors.lastname: Seifritz
authors.affiliation: Department of Neuropsychopharmacology and Brain Imaging, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland.
authors.forename: Franz X
authors.initials: FX
authors.lastname: Vollenweider
mesh_terms: D000328:Adult; D000339:Affect / Q000187:drug effects*; D000679:Amygdala / Q000187:drug effects*; D018592:Cross-Over Studies; D003863:Depression / Q000209:etiology; D004311:Double-Blind Method; D005260:Female; D006213:Hallucinogens / Q000008:administration & dosage* / Q000009:adverse effects; D064368:Healthy Volunteers / Q000523:psychology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011562:Psilocybin / Q000008:administration & dosage* / Q000009:adverse effects; D011569:Psychiatric Status Rating Scales; D055815:Young Adult
chemical_list: D006213:Hallucinogens; D011562:Psilocybin
keywords: Amygdala; Depression; Emotion; Psilocybin; Serotonin; fMRI