Challenging the amphetamine challenge test: report of an antidepressant treatment study

The primary goal of this study was to determine whether the amphetamine challenge test (ACT) response, as measured by a subjective rating scale, the How I Feel Scale (HIF), could predict antidepressant treatment outcome. Following a 1-day non-blind ACT with dextroamphetamine (d-AMPH), patients were treated double-blind for 6 weeks with either desipramine, alprazolam, or a desipramine-alprazolam combination. Regression (true score) analyses were carried out on pre- and post-ACT HIF scores and on baseline and end of study Hamilton Depression Rating Scale (HDRS) scores to determine the magnitudes of improvement measured in response to the ACT and antidepressant treatment, respectively. Regression analyses were performed on the residuals (true scores of improvement) to determine the best fitting (linear) prediction equation. Improvement in the HIF total score predicted HDRS improvement for the whole sample. Possible sources of error contributing to the outcome are identified and the results are discussed in relation to previous clinical investigations of the potential usefulness of the ACT as a predictor of antidepressant response.