What does the Keane PTSD scale of the MMPI measure? Repeated measurements in a group of patients with major depression.

We looked at a group of depressed patients in a treatment study, none of whom by study design had Posttraumatic Stress Disorder (PTSD). High scores on the PTSD (PK) scale could only be due to factors other than PTSD. Despite the absence of PTSD, we observed an extremely high false positive rate in a group given the MMPI on multiple occasions. 92% of the subjects had at least one T score at or above 65 on the PK scale. 44% of the men and the women had at least one score at or above the more conservative cutoff (a raw score of 28) recommended by Lyons and Keane. The PK scale is sensitive to depression as well as anxiety and PTSD. The PK scale showed multiple high correlations with clinical and validity scales. It was concluded, in agreement with Miller, Goldberg, and Streiner (1995) and Moody and Kish (1989), that the PK scale is primarily a measure of general dysphoria. In populations with considerable psychopathology, the PK scale does not appear to discriminate between patients with and without PTSD.