Unlike the current source density reference, frontal asymmetry was not related to lifetime MDD using the average, Cz, or linked mastoid references, which are the reference montages commonly used in the EEG asymmetry literature. Instead, the nature of the relationship between depression and EEG asymmetry was modified by current depression severity as measured by the BDI-II and sex. Analyses examining BDI-II depression groups indicated that for average and linked mastoid references, women with high levels of depressive symptoms exhibited relatively less left frontal brain activity at rest than women with low levels of depressive symptoms, with women with moderate levels of depression displaying means in between low and high groups. These findings for women replicate several studies with predominately or exclusively female samples that find current depression is linked to relatively less left than right frontal activity (see Coan and Allen, 2003, and Thibodeau et al., 2006).
