In an attempt to reconcile nonsignificant AVG, Cz, and LM results of the present study with prior research that has been based on these reference montages and that has found significant relationships between frontal EEG asymmetry and BDI-defined depressive groups (e.g., Reid et al., 1998; Schaffer et al., 1983), supplementary analyses were undertaken by creating depression groups based on a measure of current depression symptom severity, the BDI-II. Asymmetry differences as a function of BDI-II defined depression status were examined for each reference separately. This conceptualization of depression may replicate several studies that have used questionnaire indices to define depression groups in conjunction with, or instead of, DSM-IV measures of depression (see Thibodeau et al., 2006 for several examples). Three groups were established after examination of the mean and standard deviation of BDI-II intake scores across the entire sample (M = 11.1, SD = 9.6): low (BDI-II scores from 0-10; males n = 58, females n = 104), moderate (BDI-II scores from 11-20; males n = 23, females n = 65), and high (BDI-II scores 21 or greater; males n = 14, females n = 42).
