Clinical trials show which treatments work for “the average patient,” but we have little ability to predict which treat- ment will work best for any individual patient. QEEG (quantitative EEG) is a method in which a computer program reads EEG tracings and scores them alongcertaindimensions. Acompany called Aspect Medical Systems has been testing a proprietary QEEG system to see if it can predict antidepressant response. In one of the first studies to be pub- lished, 220 depressed patients under- went QEEG testing and then were given open-label Lexapro 10 mg/day. After one week of treatment, all patients were given another QEEG, and a number called the ATR (Antidepressant Treatment Response) index was calculat- ed based on each EEG. Patients were then randomly assigned in a double blind fashion to one of three treatments: a) switch to Wellbutrin, b) add Wellbutrin to Lexapro, or c) continue Lexapro. Patients with ATRs above a cer- tain threshold were 2.4 times as likely to respond to Lexapro as those with low ATRs. On the other hand, when patients with low ATR scores were assigned to Wellbutrin, they were 1.9 times as likely to respond to Wellbutrin as those low ATR patients who had remained on Lexapro. However, low ATR was not use- ful in predicting the response of patients to combination therapy (Leuchter AF et al., Psychiatry Res 2009;169:132-138).