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20-10-2011 | Mental health | Article

Antidepressant resistance in unipolar depression may predict bipolar disorder


Free abstract

MedWire News: Among patients with unipolar depression, poor response to antidepressant treatment may predict subsequent change in diagnosis to bipolar disorder, say Taiwanese researchers.

Writing in the British Journal of Psychiatry, Tung-Ping Su (Taipei Veterans General Hospital) and team explain: "The course of bipolar disorder usually begins with depression and could be diagnosed as major depressive disorder at the initial stage. This kind of hidden bipolar disorder may contribute to the treatment resistance observed in unipolar depression."

To investigate, the researchers studied data on 3944 individuals diagnosed with major depressive disorder in 2000 (n=1485) and 2003 (n=2459).

Of these, 153 (10.1%) patients from the 2000 cohort and 298 (12.1%) from the 2003 cohort subsequently had their diagnosis changed to bipolar disorder over a follow-up period of 5 and 8 years, respectively. Mean time to change in diagnosis was 3.0 and 1.9 years, respectively.

The researchers found that in the 2000 cohort, 25.6% of patients who responded poorly to antidepressant treatment had their diagnosis changed to bipolar disorder compared with just 8.9% of those with a favourable response.

Rates of diagnosis change to bipolar disorder were similar in poor and favourable antidepressant responders in the 2003 cohort, at 26.6% versus 8.6%, respectively.

Indeed, patients who were poor responders in the 2000 and 2003 cohort were 1.88 and 4.94 times more likely to have their diagnosis changed to bipolar disorder over the follow-up period than those who had a good response to antidepressant treatment, after adjustment for age, gender, and other variables.

Su and team conclude: "Our findings suggest that in individuals with major depression, a history of poor response to antidepressants is a useful sign for predicting bipolar diathesis.

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By Mark Cowen

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