Because resting frontal EEG asymmetry has demonstrated inconsistencies in its relationship to depression and emotion in previous studies, because its underlying mechanisms are poorly if at all understood, and because it is characterized by many methodological quirks (including its predominant manifestation as difference score and reference-dependent effects), resting frontal EEG asymmetry has occupied a decidedly (and deservedly) tentative status as a potential endophenotypic marker of depression (Coan & Allen, 2008). Although the present study has not entirely resolved the many methodological and theoretical mysteries long associated with frontal EEG asymmetry as an index of psychopathology, it has brought the measure significantly up to date in a larger and more representative sample of individuals than has previously been reported. If associations between frontal EEG asymmetry and depression were illusory or otherwise absent, the current study was sufficiently powered to advocate just such a conclusion. The strength of the results reported here suggests, by contrast, that associations between frontal EEG asymmetry and affective psychopathology are real, important, and worthy of considerable scientific inquiry as the pursuit of endophenotypic markers of depression vulnerability continues.
