Eye movement desensitization and reprocessing for posttraumatic stress disorder: A pilot blinded, randomized study of stimulation type

Background: Eye movement desensitization and reprocessing (EMDR) is becoming a recognized and accepted form of psychotherapy for posttraumatic stress disorder (PTSD). Yet, its mechanism of action remains unclear and much controversy exists about whether eye movements or other forms of bilateral kinesthetic stimulation contribute to its clinical effects beyond the exposure elements of the procedure. Methods: Twenty-one patients with single-event PTSD (average Impact of Event Scale score: 49.5) received three consecutive sessions of EMDR with three different types of auditory and kinesthetic stimulation (tones and vibrations): intermittent alternating right-left (as commonly used with the standard EMDR protocol), intermittent simultaneous bilateral, and continuous bilateral. Therapists were blinded to the type of stimulation they delivered, and stimulation type assignment was randomized and counterbalanced. Results: All three stimulation types resulted in clinically significant reductions of subjective units of distress (SUD). Yet, alternating stimulation resulted in faster reductions of SUD when only sessions starting with a new target memory were considered. Conclusions: There are clinically significant effects of the EMDR procedure that appear to be independent of the nature of the kinesthetic stimulation used. However, alternating stimulation may confer an additional benefit to the EMDR procedure that deserves attention in future studies.