['Depressed patients are biased in their response to negative information. They have been found to show a maladaptive behavioral and aberrant electrophysiological response to negative feedback. The aim of this study was to investigate the behavioral and electrophysiological response to feedback validity in drug-free depressed patients.', 'Fifteen drug-free in-patients with unipolar major depression disorder (MDD) and 30 demographically matched controls performed a time-estimation task in which they received valid and invalid (i.e. related and unrelated to performance) positive and negative feedback. The number of behavioral adjustments to the feedback and the feedback-related negativity (FRN) were measured.', 'Patients made fewer correct adjustments after valid negative feedback than controls, and their FRNs were larger. Neither patients nor controls adjusted their time estimates following invalid negative feedback.'] Do drug-free patients with major depression show an increased electrophysiological response to valid and invalid feedback?