EEG A1, A2, and Percent Asymmetry Indices in Major Depressive Disorder; The Importance of Symptom Severity of Depression and Anxiety

Objectives：In this study we investigated characteristics of asymmetry pattern of EEG in patients with major depressive disorder according to the severity of depression and anxiety symptoms, employing A1, A2, and Percent (PCT) asymmetry indices. Methods：Subjects involved in this study were 11 healthy controls and 11 patients with major depressive disorder who have taken no medicines for four weeks just before the study. These subjects were selected so that the two groups can have no difference in gender and age. Beck Depression Inventory (BDI), 17-item Hamilton Depression Rating Scale (HDRS), Zung’s Self-Rating Depression Scale (SDS) and Spielberger’s State-Trait Anxiety Inventory (STAI) were used to evaluate depression and anxiety symptoms, respectively. Resting EEG was recorded from F3, F4, C3, C4, T7, T8, O1 and O2 electrode sites. Results：The temporal region showed a difference in A1, A2, and PCT asymmetry indices between the depression group and the control group. Frontal (F3, F4) and temporal (T7, T8) regions showed correlation between STAI-T score and A1, A2, and PCT asymmetry indices. Conclusion：The results of this study showed that EEG A1, A2, and PCT asymmetry indices can be used as useful indices for depression. Also, it was found that trait anxiety had influence on A1, A2, and PCT asymmetry indices. (J Korean Neuropsychiatr Assoc 2007;46(2):179-184)