The neurobiology of the EEG biomarker as a predictor of treatment response in depression.

The management of depression remains a constant challenge in clinical practice. This is largely due to the fact that initial treatments frequently do not lead to remission and recovery. The current treatment approach involves lengthy trial-and-error periods. It would be beneficial to have early reliable predictors to determine whether patients will respond to treatment or not. Electroencephalography (EEG) derived biomarkers namely change in the activity of EEG frequency bands, hemispheric alpha asymmetry, theta cordance, the antidepressant treatment response index (ATR) and evoked potentials have all been shown to predict response to a variety of antidepressant medications. However, the neurobiology in support of this association has been largely unexplored. In this review, we discuss biological mechanisms for each EEG derived biomarker predictive of treatment response. Validating such biomarkers will not only greatly aid clinicians in selecting antidepressant treatment for individual patients but will also provide a critical step in drug discovery.