The effect of imaginal exposure length on outcome of treatment for PTSD.

The effects of prolonged imaginal exposure sessions (60 minutes; n=60) were compared with those of shorter exposure sessions (30 minutes, n=32) for patients with chronic posttraumatic stress disorder (PTSD). Consistent with the authors' hypothesis, patients who received 30-minute imaginal exposure sessions showed less within-session habituation than patients who received 60-minute exposure sessions. However, no differences between patients who received 60-minute and 30-minute exposure sessions emerged on improvement in PTSD-symptoms, state anxiety, depression, and end-state functioning, both at posttreatment and at 1-month follow-up. No group differences were found with regard to between-sessions habituation, number of sessions, and dropout rate. Results suggest that 30-minute imaginal exposure sessions are as effective as 60-minute exposure sessions and that within-session habituation may not be a necessary condition for successful treatment of PTSD. Future research is needed to replicate these findings and extend them to other clinical populations.