Bipolar I disorder patients with a predominant manic/hypomanic polarity (MP) are similar in temperament to those with a predominant depressive polarity (DP), but differ from patients with unipolar major depression (UP), research shows.

Writing in the Journal of Affective Disorders, Eduard Vieta (University of Barcelona, Spain) and team explain: “Recently, the concept of predominant polarity… has been introduced to further characterize subtypes of bipolar disorders.”

They add: “This concept has been proven to have diagnostic and therapeutic implications, but little is known on the underlying psychopathology and temperaments.“

To validate the concept of predominant polarity and investigate the relationship with temperament, the team studied 124 patients with bipolar I disorder and 19 with UP.

The bipolar patients were assessed for predominant polarity, with DP defined as at least two thirds of past episodes fulfilling the DSM-IV criteria for major depressive episode, and MP defined as at least two thirds of past episodes fulfilling DSM-IV criteria for manic or hypomanic episodes.

All the participants underwent temperament assessments using the Temperament Evaluation of the Memphis, Pisa, Paris, and San Diego Auto questionnaire (TEMPS-A). Temperament was assessed when patients were in full remission according to the DSM-IV criteria (no significant signs or symptoms of the disorder during the past 2 months).

The team found that 55% of the bipolar disorder patients met criteria for predominant polarity, with 47 classified as MP and 22 as DP.

Age at onset was lower in both the MP and DP bipolar groups compared with the UP group. Unipolar patients showed a longer duration of depression compared with both the MP and DP bipolar groups, but there were no significant differences in the number of suicide attempts between the groups.

Regarding temperament assessments, the mean TEMPS-A scores on the hyperthymic and cyclothymic subscales were higher in MP and DP patients compared with UP patients, while the UP group scored significantly higher than both MP and DP bipolar groups on the depressive temperament scores.

Anxious temperament scores were statistically higher in the UP group than the MP group, but did not differ between DP and UP groups. Irritable temperament scores did not differ among the three groups.

Overall, there were no significant differences in temperament profiles between the MP and DP bipolar groups.

Vieta et al conclude: “Our results show that both bipolar I MP and DP subgroups are temperamentally similar and different from UP. Depression in DP bipolar I patients should be viewed as the overlap of depression on a hyperthymic/cyclothymic temperament.”

They add: “These findings confirm the value of the predominant polarity concept as well as the importance of temperaments to separate bipolar from unipolar disorders.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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