title: Stability of symptoms across major depressive episodes in bipolar disorder.
abstract: OBJECTIVE
  Some studies suggest that depressive subtypes, defined by groups of symptoms, have predictive or diagnostic utility. These studies make the implicit assumption of stability of symptoms across episodes in mood disorders, which has rarely been investigated.
  
  
  METHODS
  We examined prospective data from a cohort of 3,750 individuals with bipolar I or II disorder participating in the Systematic Treatment Enhancement Program for Bipolar Disorder study, selecting a subset of individuals who experienced two depressive episodes during up to two years of follow-up. Across-episode association of individual depressive or hypomanic/mixed symptoms was examined using the weighted kappa measure of agreement as well as logistic regression.
  
  
  RESULTS
  A total of 583 subjects experienced two prospectively observed depressive episodes, with 149 of those subjects experiencing a third. Greatest evidence of stability was observed for neurovegetative features, suicidality, and guilt/rumination. Loss of interest and fatigue were not consistent across episodes. Structural equation modeling suggested that the dimensional structure of symptoms was not invariant across episodes.
  
  
  CONCLUSIONS
  While the overall dimensional structure of depressive symptoms lacks temporal stability, individual symptoms including suicidality, mood, psychomotor, and neurovegetative symptoms are stable across major depressive episodes in bipolar disorder and should be considered in future investigations of course and pathophysiology in bipolar disorder.
authors.affiliation: Bipolar Clinic and Research Program, Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA. rperlis@partners.org
authors.forename: Roy H
authors.initials: RH
authors.lastname: Perlis
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ostacher
authors.forename: Rudolf
authors.initials: R
authors.lastname: Uher
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Nierenberg
authors.forename: Francesco
authors.initials: F
authors.lastname: Casamassima
authors.forename: Christine
authors.initials: C
authors.lastname: Kansky
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Calabrese
authors.forename: Michael
authors.initials: M
authors.lastname: Thase
authors.forename: Gary S
authors.initials: GS
authors.lastname: Sachs
mesh_terms: D000328:Adult; D001714:Bipolar Disorder / Q000145:classification / Q000150:complications / Q000175:diagnosis; D003863:Depression / Q000209:etiology*; D003865:Major Depressive Disorder / Q000145:classification / Q000175:diagnosis* / Q000209:etiology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D012189:Retrospective Studies