Diagnostic assessment of patients was by Structured Interview for Clinical Diagnosis, patient version (SCID-P; First et al., 1994), conducted by research psychiatrists during a pretreatment session. Patients met DSM-IV criteria for major depressive disorder (n = 15) or dysthymia (n = 5). Most had unipolar depressions without melancholic or psychotic features. Three patients met criteria for Bipolar II disorder and only one for major depression with melancholic features. One patient also met criteria for social phobia and one for obsessive–compulsive disorder. Secondary analyses excluding these two patients were conducted to determine whether inclusion of patients having a comorbid anxiety disorder affected the P3 findings. Controls were interviewed using the Structured Clinical Interview for DSM-IV, nonpatient edition (SCID-NP; First et al., 1996) to exclude those with current or past DSM-IV Axis I psychopathology.
