There is no gradient in affective temperament scores from bipolar I disorder through unipolar depressive patients to healthy individuals, say UK researchers who found high dysthymic scores in both patient groups.

The concept that certain affective temperaments may represent endophenotypic manifestations of bipolar spectrum disorder vulnerability has received increased interest in recent years. Alongside this, the boundaries of bipolarity have been expanded through the emerging concept of a clinically relevant broad “bipolar spectrum,” the researchers note.

To examine the notion that there is a gradient in affective temperament scores from bipolar I disorder, through bipolar II disorder and recurrent major depression disorder (MDD-R), to healthy controls, Arianna Di Florio, from University Hospital of Wales in Cardiff, and colleagues administered the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego (TEMPS-A) to 927 individuals.

The participants consisted of 298 patients with bipolar I disorder, 108 bipolar II disorder patients (including 70 patients diagnosed with MDD-R who scored ?20 on the Hypomania Checklist [HCL-32]), 312 MDD-R patients who scored ?19 on the HCL-32, and 209 mentally healthy controls.

Bipolar II disorder patients scored highest on the cyclothymic, irritable, and dysthymic subscales of the TEMPS-A, with controls scoring lowest. On the hyperthymic subscale, bipolar II disorder patients and controls scored highest. There were no differences in median scores on the anxious subscale. However, significant differences across all four groups were found on all five subscales.

Logistic regression analysis indicated that only the dysthymic subscale distinguished between patients and controls, with all three groups differing significantly from controls. There were no significant differences among the patient groups when taking into account number of manic and depressive episodes and age at onset.

Interestingly, the anxious subscale was able to distinguish between MDD-R patients and controls, with no other associations identified, the team writes in the Journal of Affective Disorders.

They conclude: “These data suggest that dysthymic temperament may be a common intermediate phenotype in affective disorders.”

The researchers add: “We failed to find evidence to support the hypothesis that affective temperament scores show a gradient between bipolar I disorder, bipolar II disorder, MDD-R, and controls.”

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; 2009

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