Predictors for Switch From Unipolar Major Depressive Disorder to Bipolar Disorder Type I or II: A 5-Year Prospective Study

K. Mikael Holma, M.D.; Tarja K. Melartin, M.D., Ph.D.; Irina A. K. Holma, M.D.; and Erkki T. Isometsä, M.D., Ph.D.

Objective: The primary objective was to compare the efficacy and tolerability of quetiapine and risperidone in the treatment of mood symptoms, drug cravings, and drug use in outpatients with concurrent DSM-IV-defined bipolar I or II disorder and cocaine or methamphetamine dependence.

Method: The Vantaa Depression Study included at baseline 269 psychiatric outpatients (82.9%) and inpatients (17.1%) with DSM-IV MDD, diagnosed using structured and semistructured 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.

Conclusion: 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.

(J Clin Psychiatry 2008;69:1267-1275. Online Ahead of Print July 29, 2008.)

Received Nov. 7, 2007; accepted Dec. 24, 2007. From the Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki (all authors); Helsinki University Central Hospital (HUCH), Peijas Hospital, Healthcare District of Helsinki and Uusimaa, Vantaa (Dr. Melartin); and the Department of Psychiatry, HUCH, Healthcare District of Helsinki and Uusimaa, Helsinki (Dr. Isometsä), Finland.

This study was supported by grants from the Academy of Finland and the Healthcare District of Helsinki and Uusimaa in Finland.

The authors report no additional financial or other relationship relevant to the subject of this article.

Corresponding author and reprints: Erkki T. Isometsä, M.D., Ph.D., Institute of Clinical Medicine, Department of Psychiatry, P.O. Box 22 (Välskärinkatu 12 A), 00014 University of Helsinki, Finland (e-mail: erkki.isometsa@hus.fi).