[Construction and validation of a dimensional scale for mood disorders: multidimensional assessment of thymic states...

The heterogeneity of mood episodes in bipolar disorders makes it difficult in some cases to define appropriate therapeutic strategies. Therefore, we proposed a new tool based on a dimensional approach, with five a priori subscales (emotional reactivity, thought processes, psychomotricity, motivation and sense perception) expected to help define subgroups of mood episodes predictive of the response to treatment. This study was designed to validate this multidimensional assessment of thymic states (MAThyS) scale.

One hundred and ninety six subjects were included: 44 controls and 152 bipolar patients in various states: euthymic, manic or depressed. The MAThyS is a visual analog scale consisting of 20 items, ranging from inhibition to excitation. These items corresponded to five dimensions, namely: emotional reactivity, thought processes, psychomotricity, motivation and sense perception. They were selected since they represent clinically relevant quantitative traits.

Confirmatory analyses demonstrated a good validity for this scale, fair convergent and divergent validity (multitrait multimethod analyses (MTMM)), good internal consistency both at global and dimensional level (Alpha Cronbach ranging from 0.70 to 0.93). The MathyS scale is moderately correlated with both the Montgomery and Asberg depression rating scale (MADRS) (depression score; r=-0.45) and the mania rating scale (MAS) (manic score; r=0.56). Some dimensions were linked (emotional reactivity and thought processes, r=0.71; psychomotricity and motivation, r=0.70). Analysing the divergent validity of items led us to redefine three of them. Following this validation step, exploratory analyses suggest that a four-dimension factorial structure is more appropriate. However, the statistical model is very close to the clinically relevant five-dimensional model. Further studies are needed to explore the relevance of retaining this dimension as a useful descriptive element.