Cordance as a biomarker in sleep-EEG for treatment response in depression

Cordance is a new quantitative EEG-method with at least 19 electrodes, which has shown usability as a biomarker for depression within the waking-state. We tested whether differences in cordance derived from sleep EEG exist between responders and non-responders after antidepressant medication. Additionally, we compared these with healthy subjects. 20 in-patients (15 women, 5 men) with a depressive episode were treated with various antidepressants of “doctor's choice”. All patients slept two consecutive nights in our sleep laboratory, the first night serving as adaptation to the laboratory setting. 19 conventional surface electrodes were placed according to the international 10 – 20 system as in previous cordance studies. Related to the algorithm of Leuchter and Cook, we also chose unique, exclusive 30 s of artefact free EEG data. Eight responders compared to 12 non-responders showed higher cordance values in prefrontal EEG-sites (z-score -1.52 ± 0.98 versus -2.52 ± 0.71; F (1.18)= 7.123, p = 0.016) after first week of treatment, and z-scores of the prefrontal sites correlated with HAM-D scores of all patients (Spearmans Rho: R =-0.5; p = 0.025). The healthy subjects showed cordance values similar to the responders at first week, but not to the non-responders. These results suggest that cordance derived from sleep EEG already at first week of treatment provides a predictor for the response to antidepressant treatment in depressed patients.