The nature and course of subthreshold PTSD.

This study investigated rates of subthreshold PTSD and associated impairment in comparison to no PTSD and full PTSD and prospectively followed the course of subthreshold symptoms over 3 years. 3360 workers dispatched to the WTC site following 9/11 completed clinician interviews and self-report measures at three time points each one year apart. At Time 1, 9.7% of individuals met criteria for subthreshold PTSD. The no PTSD, subthreshold PTSD, and full PTSD groups exhibited significantly different levels of impairment, rates of current MDD diagnosis, and self-reported symptoms of depression. At Time 2, 29% of the initial sample with subthreshold PTSD continued to meet criteria for subthreshold or full PTSD; at Time 3, this was true for 24.5% of the initial sample. The study lends credence to the clinical significance of subthreshold PTSD and emphasizes that associated impairment may be significant and longstanding. It also confirms clinical differences between subthreshold and full PTSD.