Understanding the pattern of PTSD symptomatology: a comparison of between versus within-group approaches.

This report examines the influence of statistical approach on patterns of Posttraumatic Stress Disorder (PTSD). In this report, 114 women and 51 men were assessed using both the Clinician Administered PTSD Scale (CAPS) and the Posttraumatic Symptom Scale-Self Report measure (PSS-SR). Data were examined using both a between-group and a within-group design. In the between-group approach, three subsamples were formed, representing full syndrome PTSD (fPTSD), partial PTSD (pPTSD), and no PTSD. The fPTSD and pPTSD groups differed on total scores on both PTSD measures, although differences were noted between clinician and self-report measures in specific symptom clusters. In the within-group approach, curve estimation techniques were used to examine linear versus quadratic fit of the data, utilizing the sample as a whole, ranked according to a separate scale of clinical severity. A linear approach was noted for each measure. Results are discussed in light of current design choices in the literature and its impact on the understanding of post-trauma problems.