Introduction: Bipolar disorder (BD) in DSM-III and DSM-IV is classified as a mood disorder and requires the presence of a mood change, i.e., euphoria or irritability. Differently, DSM-5 states that there must be some increase in energy or motor activity in addition to the mood change.
Objective: Our aim was to identify which types of symptoms (i.e., mood- or energy/activity-related symptoms) are the most informative in a manic episode.
Method: Symptoms of manic episodes in 106 outpatients with BD were assessed through the Young Mania Rating Scale between November 2002 and November 2015 in a naturalistic study. The items of the scale were divided into three groups according to clinical criteria: mood, energy/activity, and other. The Samejima Graded Response Model of the Item Response Theory was computed as well as the Test Information Function for comparisons between groups. Chi-squared tests were used to verify the association between the groups of symptoms by comparing the area under the curve of the TIF results.
Results: The information accounted for energy/activity represents 77% of the proportion of the total TIF; about 23% is related to mood and other groups of symptoms. Both proportions are statistically different (X2(1) = 30.42, p < 0.001).
Conclusion: On average, changes in energy/activity tend to be more informative than mood changes during the manic phases of BD.
Keywords: Bipolar disorder; Young Mania Rating Scale; energy; mood changes; motor activity.