The value of these alpha scores for predicting treatment response was examined by classifying patients as to whether they had prominent alpha above the median for controls (dotted line in Fig. 3; predicted responders), or less alpha than the control median (predicted nonresponders). By this classification, 14 of the 15 patients with prominent alpha responded to treatment, whereas only 14 of 26 with less alpha were responders (Fisher’s exact test, 2-tail p = .014). This indicates that prominent alpha had a high positive predictive value of 93.3 (response rate for those predicted to be responders) and specificity of 92.3 (percentage of nonresponders predicted to be nonresponders). In contrast, sensitivity was only 50.0, and negative predictive value 46.1, with an overall predictive value of 63.4. Eyes-closed-minus-open alpha was also significantly correlated with post-treatment HAM-D (r = −.35, n = 35, p = .04), but not with pretreatment HAM-D (r = −.14, n = 41, ns) or BDI (r = −.12, n = 39, ns). Logistic regression also indicated that posterior condition-dependent alpha was predictive of treatment response (Wald test = 6.183, df = 1, p = .013).
