Envelope of Alpha Activity in Depression and Anxiety: A Novel Analysis of the Second-Order Derivatives of Alpha Envelope of EEG

This study examined the relationship between alpha activity fluctuations in resting-state electroencephalography (EEG) and the Beck Depression Inventory (BDI) and State-Trait Anxiety Inventory (STAI) scores. A novel approach was introduced using second-order derivatives of the alpha envelope to identify potential functional biomarkers for depression and anxiety conditions. Two 30-s eyes-closed epochs of 64-channel EEG data were collected from open dataset of 113 college-aged participants with the BDI and STAI scores. Metrics including mean positive (Ap) and negative (An) second-order derivatives, the Ap-An ratio, root mean square (RMS), and peak frequency of the alpha envelope were extracted. Correlations between these EEG metrics and scores on the BDI and STAI were analyzed. BDI (Spearman's rank correlation, rs = 0.253-0.304,) and STAI (rs = 0.222-0.339) scores showed significant but weak positive correlations with the Ap-An ratio, in the left frontal regions (<i>P</i> < .05, FDR-corrected). No significant correlation was found between envelope amplitude and either score. The Ap-An ratio at the frontal, temporal, and central electrodes, and peak alpha frequency at the electrodes including the parietal and occipital regions, were significantly higher in participants with BDI scores above 10 compared to those with scores of 10 or below (<i>P</i> < .05, FDR, Mann-Whitney U test). These findings suggest that the second-order derivatives of alpha envelope may serve as functional biomarkers for psychiatric disorders, differently from the frequency and amplitude. Further research is needed to confirm whether these EEG features reflect regional neural activity, such as excitatory and inhibitory activities.