Issues in the design of multisite clinical trials of psychotherapy: VA Cooperative Study No. 494 as an example.

This article describes issues in the design of an ongoing multisite randomized clinical trial of psychotherapy for treating posttraumatic stress disorder (PTSD) in female veterans and active duty personnel. Research aimed at testing treatments for PTSD in women who have served in the military is especially important due to the high prevalence of PTSD in this population. VA Cooperative Study 494 was designed to enroll 384 participants across 12 sites.