Background Subtle electroencephalographic (EEG) abnormalities have been detected among subjects with depressed affect. The present study attempted to discern whether these abnormalities reflect a main effect or an interaction between depression and either of two family history variables—a family history of alcoholism or a family history of depression.
Methods The subjects were 151 adolescent females, aged 14 to 20 years, of whom 58 met DSM-III-R diagnostic criteria for a lifetime history of a major depressive episode. The electroencephalogram was recorded from 31 electrode sites while the subjects sat relaxed, with their eyes open, for 5 min.
Results Analyses of EEG data revealed that a personal history of depression and a family history of alcoholism had opposite effects on the EEG power spectrum. Depression was associated with an increase in α power (7.5–12.5 Hz). In contrast, a family history of alcoholism was associated with an increase in fast β power (19–30 Hz) and a decrease in θ power (4–7 Hz). There were no significant main or interactive effects of a family history of depression. Current source density topographic analyses of the significant group differences in α and fast β power demonstrated that the effects of depression could be localized to the right frontal brain, whereas the effects of a family history of alcoholism were localized to the left frontal area.
Conclusions The laterally opposite effects of depression and a family history of alcoholism suggest a high level of functional differentiation of the frontal brain. They also suggest that the different neurophysiological substrates of depression and familial risk can be distinguished through the use of modern methods of EEG source localization.