A case-control study of bipolar depression, compared with unipolar depression, in a regional hospital in Hong Kong.
OBJECTIVE
To determine the characteristics of diagnostic conversion from unipolar depression to bipolar depression in psychiatric outpatients, and to compare the profiles of the 2 groups of patients.


METHODS
This is a case-control study in which outpatients newly diagnosed with unipolar depression were reviewed. Outpatients who had polarity conversion to bipolar depression were recruited as subjects and control subjects were matched. The diagnostic validity was enhanced by clinical interview, review of case records by an independent specialist psychiatrist, and administration of the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Axis I Disorders. Multivariate conditional logistic regression was carried out to identify the predictors of bipolar switch.


RESULTS
Eighty-eight subjects among those who maintained regular outpatient clinic follow-up (n = 823) showed bipolar switch during the period under study. The incidence of polarity conversion was 10.7%. Bipolar switch was associated with family history of bipolar affective disorder, use of 3 or more different types of antidepressants in the first 5 years after presentation, an earlier age at presentation of depressive symptoms of less than 37 years, and males.


CONCLUSIONS
Change in diagnostic polarity is not uncommon in Chinese psychiatric outpatients initially presenting with unipolar depression. They share some common risk factors as identified in Western studies. These can be helpful to clinicians as guidance for identification of patients with depression at high risk for a bipolar course.
Wong
Sze-man
SM
Department of Psychiatry, Pamela Youde Nethersole Eastern Hospital, Chai Wan, Hong Kong. qsmwong@hotmail.com
Dunn
Lai-wah
LW
Tang
Wai-nang
WN
Chan
Wah-fat
WF
Chong
Shiu-yin
SY
D000328:Adult; D000928:Antidepressive Agents / Q000009:adverse effects / Q000627:therapeutic use; D001714:Bipolar Disorder / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics / Q000523:psychology; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D003866:Depressive Disorder / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology / Q000523:psychology; D003937:Diagnosis, Differential; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004351:Drug Resistance; D005260:Female; D006723:Hong Kong; D006786:Hospitals, Urban; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D018570:Risk Assessment
D000928:Antidepressive Agents