Can the Loudness Dependence of Auditory Evoked Potentials and Suicidality Be Used to Differentiate between Depressive Patients with and without Bipolarity

Objective This study aimed to test the hypothesis that the loudness dependence of auditory evoked potentials (LDAEP) can be used to predict the presence of bipolarity in patients with major depressive episodes. Methods A cohort of 61 patients who met the criteria for major depressive disorder (MDD) following diagnosis using Axis I of the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders-text revision, and who had no history of hypomanic or manic episodes was included in this study. The patients were stratified into two subgroups based on whether or not they achieved a positive score for the Korean versions of the Mood Disorder Questionnaire (K-MDQ). The LDAEP was evaluated by measuring the auditory event-related potentials before beginning medication with serotonergic agents. Results The Barratt Impulsiveness Scale (BIS) score was also higher for the positive screening group (81.24 +/- 11.87) than for the negative screening group (73.30 +/- 14.92; p=0.039, independent t-test). However, the LDAEP, Beck Depression Inventory Hamilton Depression Rating Scale, Beck Hopelessness Scale (BHS), and Hamilton Anxiety Scale scores did not differ significantly between them. When binary logistic regression analysis was carried, the relationship between the positive or negative subgroups for K-MDQ and BIS or Beck Scale for Suicidal Ideation (BSS) score was also significant (respectively, p=0.017, p=0.038). Conclusion We found that LDAEP was not significantly different between depressive patients with and without bipolarity. However, our study has revealed the difference between two subgroups based on whether or not they achieved a positive score for the K-MDQ in BIS or BSS score.