A considerable number of older patients with bipolar II disorder or bipolar disorder not otherwise specified (BP-II/BP-NOS) are initially misdiagnosed as having major depressive disorder (MDD), study findings show.

As monotherapy with antidepressants can have adverse effects in elderly patients with bipolar disorder as well as in younger patients, the researchers call for clinicians to keep “the soft forms of bipolar disorder in the differential diagnosis for late-life depression.”

They found that younger age at onset of the first major depressive episode, more frequent prior major depressive episodes, and the existence of depressed mixed state could help clinicians identify elderly bipolar patients.

Minoru Takeshima and Koichi Kurata, from Ishikawa Prefectural Takamatsu Hospital in Kahoku City in Japan, reviewed the medical charts of 87 patients aged at least 60 years who had been hospitalized due to a major depressive episode.

The final diagnoses were MDD in 55 (63.2%) patients and bipolar disorder in 32 (36.8%) patients. Among the bipolar disorder diagnoses, six were for bipolar I disorder, 24 were for BP-II, and two were for BP-NOS.

The researchers note, however, that most of the 26 patients with BP-II/BP-NOS had initially been misdiagnosed. Nineteen (73%) were initially diagnosed with MDD (61.0%) or other disorders (dementia, adjustment disorder; 12.0%).

In contrast, only 9.0% and 34.0% of patients who were finally diagnosed with MDD or bipolar I disorder, respectively, were initially misdiagnosed.

The results, published in the Journal of Affective Disorders, show that patients with BP-II/BP-NOS were significantly younger than patients with MDD at the onset of the first major depressive episode, at a median of 52 versus 66 years.

In addition, patients with BP-II/BP-NOS were significantly more likely to have three or more major depressive episodes than were patients with MDD, at a rate of 40.0% versus just 5.5%.

Depressed mixed state also distinguished patients with BP-II/BP-NOS from those with major depressive disorder, occurring in 61.5% and 16.4% of patients, respectively.

Multiple logistic regression analysis confirmed that younger age at onset of first major depressive episode (odds ratio [OR]=0.94) and depressed mixed state (OR=6.22) were independent markers of bipolarity.

The researchers conclude: “The present study showed that a considerable number of older patients who were hospitalized due to major depressive episode had been initially misdiagnosed with MDD and were actually BP-II/BP-NOS patients, similar to younger bipolar cohorts, in whom such misdiagnosis is a major problem.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

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