Posttraumatic Symptom Scale - Interview Version (PSS-I)

Summary   

The PSS-I is a widely utilized PTSD measure administered by an interviewer. It is a semi-structured interview providing a categorical diagnosis, as well as a measure of the severity of PTSD symptoms as defined by DSM-IV. It can be administered by any trained person and takes 15-25 minutes. The PSS-I has been validated for two time intervals: "past 2 weeks" and "past month".

Author/publisher details   

The PSS-I was first published by Foa et al (1993):
Edna B. Foa,
Center for the Study and Treatment of Anxiety
University of Pennsylvania
3535 Market Street, 6th Floor
Philadelphia, PA 19104

Date   

1993

Description   

The PSS-I is a semi-structured interview for PTSD assessment and diagnosis. It consists of 17 items corresponding to the DSM-IV PTSD symptoms, assessing re-experiencing, avoidance and hyperarousal symptoms. Items are rated on 0-3 scales for combined frequency and severity, yielding one score per item. A score of 0 corresponds to "not at all"; 1 corresponds to "once per week or less/a little"; 2 corresponds to "2 to 4 times per week/somewhat"; 3 corresponds to "5 or more times per week/very much." It takes 15-25 minutes to administer, (depending on the level of psychopathology) and less than 1 minute to score. Some training is required to administer this test, although a very detailed, self-explanatory manual is provided. Both the scale and the manual are free.

Scoring and Psychometrics   

Scoring
The PSS-I is scored by simply summing the individual item scores. To obtain severity scores for each of the reexperiencing, avoidance, and hyperarousal clusters, sum the items within each cluster. To obtain total PTSD severity, sum all 17 items.

Psychometrics
The PSS-I has excellent psychometric properties. Inter-rater reliability for PTSD diagnosis (k = .91) and overall severity (r = .97) are excellent (Foa et al., 1993). In a recent examination the inter-rater reliability for symptom severity was .94 (Foa et al, 2005). Foa and Tolin (2000) reported that the PSS-I and the CAPS had equally high internal consistency; the PSS-I yielded slightly higher inter-rater reliability than the CAPS; the CAPS and PSS-I correlated strongly with each other and with the SCID. Overall the CAPS and PSS-I performed equally well. Thus, the time needed for assessing PTSD with the PSS-I is relatively short without sacrificing reliability or validity.

Key/core References   

Foa, E.B., Hembree, E.A., Cahill, S.P., Rauch., S.A.M., Riggs, D.S., Feeny, N.C., &Yadin, E. (2005) Randomized Trial of prolonged Exposure for PTSD with and without Cognitive Restructuring Outcome at Academic and Community Clinics. Journal of Consulting and Clinical Psychology. 73, 953-964.

Foa, E. B., Riggs, D. S., Dancu, C. V., & Rothbaum, B. O. (1993). Reliability and validity of a brief instrument for assessing post-traumatic stress disorder. Journal of Traumatic Stress, 6, 459-473.

Foa, E.B. & Tolin, D.F. (2000) Comparison of the PTSD Symptom Scale-Interview Version and the Clinician-Administered PTSD Scale. Journal of Traumatic Stress, 13,181-91

Further Information   
(e.g., Links)   

Information about training and using the PSS-I can be obtained from Edna B. Foa or Elizabeth Hembree, Center for the Study and Treatment of Anxiety. Email: Foa@mail.med.upenn.edu or Hembree@mail.med.upenn.edu

View manual   

ISTSS Members: Download PSS-I Manual.

View tool   

This resource should be used in an ethical and responsible manner and should be used only for the purpose(s) for which it has demonstrable validity. Please observe copyright where indicated and reference it appropriately.

ISTSS Members: Download PSS-I Symptom Scale Interview