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11-10-2011 | Mental health | Article

Antidepressant-induced mania similar to bipolar disorder


Free abstract

MedWire News: Depressive patients with antidepressant-induced "manic switches" show similar clinical features as individuals with bipolar disorder, research shows.

The findings suggest that depressive patients with these manic switches be classified and treated as true bipolar patients, write Zeliha Tunca (Dokuz Eylul University, School of Medicine, Izmir, Turkey) and colleagues in the Journal of Affective Disorders.

Antidepressant medication can induce a manic switch in patients with depression, but manic-switch episodes are not considered bipolar disorder in the DSM-IV.

In this study, the researchers compared the clinical characteristics of 58 patients with bipolar disorder I and 18 patients with bipolar type II, both having first-episode depression, with those of 61 patients with a history of treatment-induced mania, and 80 patients with unipolar depression.

Bipolar I patients had the earliest age of symptom onset, an average of 25.2 years, significantly earlier than the other three groups of patients (33.7, 31.2, and 35.4 years, respectively).

Patients with treatment-induced mania had similar numbers of past depressive episodes compared with the bipolar I and II patients (3.66 vs 3.65 and 3.72, respectively), but significantly longer durations of illness (17.11 vs 11.41 and 10.17 weeks, respectively).

In addition, patients with treatment-induced mania had the highest frequency of depressive illness, a greater presence of melancholic features, and were more likely to have atypical features of illness, including seasonality, than those with either bipolar disorder.

That said, the most severe depressive episodes occurred equally in "switch" and bipolar disorder patients.

Cluster analysis using characteristics of the illness revealed that manic-switch patients clustered together with bipolar patients, with unipolar depression patients in a separate group.

Importantly, prior to the switch-induced mania, these patients showed similar characteristics of disease to the depressive illness of bipolar patients.

These findings "supports the proposal that antidepressant-induced switching may represent an acceleration of the natural course of bipolar disorder," report Tunca and colleagues.

They conclude: "The findings of this study confirm that treatment-induced mania is a clinical phenomenon that belongs within the bipolar spectrum rather than a coincidental treatment complication, and that it should be placed under 'bipolar disorders' in future classification systems."

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