title: Differences in cognitive factors between "true drug" versus "placebo pattern" response to fluoxetine as defined by pattern analysis.
abstract: OBJECTIVE
  Pattern analysis has identified two types of response patterns to antidepressants: "true drug" response (TDR) and "placebo pattern" response (PPR). This study examines the relationship between cognitive factors and TDR and PPR to fluoxetine.
  
  
  METHODS
  We assessed 310 outpatients meeting DSM-III-R criteria for major depressive disorder (MDD) who were enrolled in an 8-week open trial of fluoxetine 20 mg/day. Response patterns were determined using the clinical global impressions-improvement (CGI-I). We administered the following self-rated scales to all patients at the baseline visit and at endpoint: perceived stress scale (PSS), cognitions questionnaire (CQ), Beck hopelessness scale (BHS) and dysfunctional attitudes scale (DAS).
  
  
  RESULTS
  One hundred and thirty-four patients had TDR, 66 patients had PPR, and 110 patients were non-responders (NR). Demographic variables and severity of depression at baseline (HAMD-17) were not significantly different between the two response pattern groups. We compared cognitive factors before and after treatment across patients with TDR and PPR, and there were no significant differences at baseline in CQ, PSS, BHS, and DAS scores. At endpoint, outpatients with PPR had significantly lower scores on the PSS (p < 0.001) compared to the patients with TDR, even after adjusting for multiple comparisons and severity of depression at endpoint.
  
  
  CONCLUSIONS
  Significant differences in cognitive/psychological factors, specifically lower post-treatment perceived stress, accompany "placebo" pattern of response to antidepressant treatment and differentiate it from "true drug" response pattern, as defined by pattern analysis.
authors.affiliation: Depression Clinical and Research Program, Massachusetts General Hospital, Harvard Medical School, Boston, USA. afarabaugh@partners.org USA.
authors.forename: Amy H
authors.initials: AH
authors.lastname: Farabaugh
authors.forename: Shamsah B
authors.initials: SB
authors.lastname: Sonawalla
authors.forename: Maurizio
authors.initials: M
authors.lastname: Fava
authors.forename: Paola
authors.initials: P
authors.lastname: Pedrelli
authors.forename: George I
authors.initials: GI
authors.lastname: Papakostas
authors.forename: Faye
authors.initials: F
authors.lastname: Schwartz
authors.forename: David
authors.initials: D
authors.lastname: Mischoulon
mesh_terms: D000328:Adult; D003071:Cognition / Q000187:drug effects*; D003865:Major Depressive Disorder / Q000188:drug therapy* / Q000523:psychology; D005260:Female; D005473:Fluoxetine / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015990:Placebo Effect; D013315:Stress, Psychological / Q000523:psychology
chemical_list: D005473:Fluoxetine