Disorder specificity despite comorbidity: resting EEG alpha asymmetry in major depressive disorder and post-traumatic stress disorder.

The approach-withdrawal and valence-arousal models highlight that specific brain laterality profiles may distinguish depression and anxiety. However, studies remain to be conducted in multiple clinical populations that directly test the diagnostic specificity of these hypotheses. The current study compared electroencephalographic data under resting state, eyes closed conditions in patients with major depressive disorder (MDD) (N=15) and post-traumatic stress disorder (PTSD) (N=14) relative to healthy controls (N=15) to examine the specificity of brain laterality in these disorders. Key findings included (1) reduced left-frontal activity in MDD, (2) a positive correlation between PTSD severity and right-frontal lateralisation, (3) greater activity in PTSD patients relative to MDD within the right-parietotemporal region, and (4) globally increased alpha power in MDD. Findings partially support the diagnostic applicability of the theoretical frameworks. Future studies may benefit from examining task-driven differences between groups.