title: Predictors for switch from unipolar major depressive disorder to bipolar disorder type I or II: a 5-year prospective study.
abstract: OBJECTIVE
  In this naturalistic study, we investigated the rate, time course, and predictors of a diagnostic switch from unipolar major depressive disorder (MDD) to bipolar disorder type I or II during a 5-year follow-up.
  
  
  METHODS
  The Vantaa Depression Study included at baseline 269 psychiatric outpatients (82.9%) and inpatients (17.1%) with DSM-IV MDD, diagnosed using structured and semi-structured interviews and followed up at 6 months, 18 months, and 5 years between February 1, 1997 and April 30, 2004. Information on 248 MDD patients (92.2%) was available for analyses of the risk of diagnostic switch. Cox proportional hazards models were used.
  
  
  RESULTS
  Twenty-two subjects (8.9%) with previous unipolar MDD switched to bipolar disorder type II and 7 (2.8%) to type I. Median time for switch to bipolar type I was significantly shorter than to type II. In Cox proportional hazards analyses, severity of MDD (hazard ratio [HR] = 1.08, 95% CI = 1.00 to 1.15, p = .036), obsessive-compulsive disorder (OCD) (HR = 5.00, 95% CI = 2.04 to 12.5, p < .001), social phobia (HR = 2.33, 95% CI = 1.00 to 5.26, p = .050), and large number of cluster B personality disorder symptoms (HR = 1.10, 95% CI = 1.02 to 1.20, p = .022) predicted switch.
  
  
  CONCLUSIONS
  Among outpatients with MDD in secondary level psychiatric settings, diagnostic switch to bipolar disorder usually refers to type II rather than type I. The few switching to bipolar type I do so relatively early. Predictors for diagnostic switch include not only features of mood disorder, such as severity, but may also include some features of psychiatric comorbidity, such as concurrent social phobia, OCD, and symptoms of cluster B personality disorders.
authors.affiliation: Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland.
authors.forename: K Mikael
authors.initials: KM
authors.lastname: Holma
authors.forename: Tarja K
authors.initials: TK
authors.lastname: Melartin
authors.forename: Irina A K
authors.initials: IA
authors.lastname: Holma
authors.forename: Erkki T
authors.initials: ET
authors.lastname: Isometsä
mesh_terms: D000328:Adult; D001714:Bipolar Disorder / Q000175:diagnosis* / Q000523:psychology*; D003865:Major Depressive Disorder / Q000175:diagnosis* / Q000523:psychology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008297:Male; D009771:Obsessive-Compulsive Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D010554:Personality Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D010555:Personality Inventory; D010698:Phobic Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D011237:Predictive Value of Tests; D011446:Prospective Studies