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25-03-2013 | Mental health | Article

Subtle differences in bipolar, unipolar depression


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medwireNews: In the absence of information regarding mania and hypomania symptoms, a number of depression-related differences may help identify bipolar disorder (BD) in patients who have been misdiagnosed with major depressive disorder (MDD), suggest Chinese researchers.

Yu-Tao Xiang (Chinese University of Hong Kong) and colleagues found that BD patients misdiagnosed with MDD had more atypical depressive features, more psychotic symptoms, a higher number of previous depressive episodes, and an earlier age at onset than those with a correct MDD diagnosis.

"Although there are currently no widely accepted diagnostic dividing lines between BD depression and MDD in clinical practice, our results indicate that there are subtle differences between the forms of depressive episodes occurring in the context of BD and MDD, the clinical use of which might be helpful in distinguishing BD from MDD in Chinese patients," they write in Bipolar Disorders.

The findings come from a study of 1487 patients initially diagnosed with MDD who were evaluated at 13 psychiatric hospitals or psychiatric units.

Using the Mini-International Neuropsychiatric Interview, the team found that 309 (20.8%) patients met DSM-IV criteria for BD, with 118 (7.9%) meeting criteria for BD I and 191 (12.8%) for BD II.

Multiple logistic regression analyses revealed that BD I patients were more likely than MDD patients to have atypical depression symptoms (39.8 vs 15.2%), such as increased appetite, increased sleep, and weight gain, at an odds ratio (OR) of 2.0, and psychotic symptoms (38.1 vs 13.4%), at an OR of 2.1.

In addition, they had more lifetime depressive episodes than MDD patients (mean 3.9 vs 1.9) and an earlier mean age at depression onset (28.0 vs 34.6 years).

BD II patients were also more likely than MDD patients to have psychotic symptoms (28.8%), at an OR of 2.1, and had an earlier mean age at depression onset (28.8 years).

Among patients with BD, those with BD I were more likely to have experienced more than four depressive episodes per year than those with BD II (29.7 vs 8.9%), at an OR of 3.1.

Xiang and team conclude: "Depressive episodes in the context of BD I and BD II, among those who were misclassified as MDD, present some different clinical features compared to MDD.

"This finding should be taken into account in guiding diagnostic practices in China."

medwireNews ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Mark Cowen, Senior medwireNews Reporter

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