Defining bipolar mood states with quantitative measurement of inhibition/activation and emotional reactivity

Mood state heterogeneity in bipolar disorder leads to confusion in diagnosis and therapeutic strategies. Recently, the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) showed that two-thirds of bipolar-depressed patients had concomitant manic symptoms, these characteristics being linked to a more severe form of bipolar disorder. Moreover, manic symptoms occurring during bipolar depression are associated with mood switches induced by antidepressant. It is thus important to best characterize mood episodes with mixed features in order to improve our understanding of the etiopathology and to choose the most appropriate treatment. As dimensional approach can better describe phenomena that are distributed continuously without clear boundaries, we used the MATHYS scale, constructed on a dimensional approach. The aim of the study is to determine whether two dimensions (activation/inhibition and emotional reactivity) improve assessment of bipolar states in which both manic and depressive symptoms are associated.

We included 189 bipolar patients and 90 controls. Bipolar patients were distinguished between those with a major depressive episode without manic symptoms, a major depressive episode with manic symptoms, a mixed state and a manic state. The MATHYS scale provides a total score, quantifying an inhibition/activation process, and a score for emotional reactivity (intensity of emotions).

We demonstrated that there is a continuum ranging from inhibition to activation (respectively from major depressive episodes without manic symptoms to manic states), with a gradual increase in the severity of the activation. Regarding emotional reactivity, results are quiet different since only major depressive episodes without manic symptoms are characterized by emotional hypo-reactivity while major depressive episodes with manic symptoms, manic and mixed states exhibited emotional hyper-reactivity.

The MATHYS scale, providing a score for inhibition/activation process and a score for emotional reactivity, is clearly useful to distinguish bipolar depressive episodes without manic symptoms from those with manic symptoms. This last type of depression appears to belong to a broad spectrum of mixed state. To go further we need to explore if these two types of depression are underlined by different mechanisms and what is the most appropriate treatment for each of them.