Predictors for Switch From Unipolar Major Depressive Disorder to Bipolar Disorder Type I or II: A 5-Year Prospective Study
J Clin Psychiatry 2008;69(8):1267-1275
© Copyright 2014 Physicians Postgraduate Press, Inc.
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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.
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.