Sensitivity and concurrent validity of the Japanese version of the Euthymia scale: a clinimetric analysis

Background: Euthymia is characterized by the lack of mood disorders, the presence of positive affects, psychological flexibility and well-being, a unifying outlook on life, and resistance to stress. The Euthymia Scale (ES) is a 10-item self-rating clinimetric index assessing euthymia. Objectives: The present study was conducted to examine the clinimetric sensitivity and concurrent validity of the Japanese version of the Euthymia Scale (ES-J). Methods: A cross-sectional online survey was conducted. The Mini-International Neuropsychiatric Interview was used to determine the presence of past or current major depressive episodes (MDE). The clinimetric sensitivity was evaluated using the Analysis of Variance (ANOVA). Pearson’s correlation coefficients were performed to examine the concurrent validity of the ES-J. Results: A total of 1030 eligible participants completed the survey. The ES-J differentiated healthy subjects from complete remission (i.e., those with a past history of MDE without current MDE) (p < 0.001), from those with past or current history of MDE (p < 0.001), subjects with current MDE from those with sub-threshold symptoms of depression (p < 0.001), and healthy participants from subjects with moderate to severe symptoms of psychological distress (p < 0.001). The associations between the ES-J and measures of psychological well-being, resilience, life satisfaction, and social support were significantly positive (0.353 < r < 0.666, p < 0.001). A negative relationship between the ES-J and measures of psychological distress was also found (r = − 0.595, p < 0.001). Conclusions: The findings of the present study indicated that the ES-J is a valid and highly sensitive clinimetric index, which can be used as a screening measure in the clinical process of assessment of recovery, particularly when symptoms are expected to be mild and/or when dealing with subclinical symptoms of psychological distress and depression. The findings of this study also support the use of the ES-J to detect vulnerability to depression and to identify subjects at higher risk of relapse.