Fig. 3
Correlation analysis between PHQ-9 scores and relative spectral power at the forehead. (A) Pearson correlation coefficients between PHQ-9 scores and relative spectral power across the 4–20 Hz frequency range. The x-axis represents frequency (Hz), and the y-axis represents the Pearson correlation coefficient (r). The red line denotes male participants, and the blue line denotes female participants. (B) Scatter plots of PHQ-9 scores versus relative spectral power at 11.9 Hz. Red dots represent male participants (r = 0.40, p = 0.011), and purple dots represent female participants (r = 0.33, p = 0.037).
