Telephone-guided imagery rehearsal therapy for nightmares: Efficacy and mediator of change.

The currently best-supported psychological treatment for nightmares is imagery rehearsal therapy. The problem, however, is that not enough trained practitioners are available to offer this treatment. A possible solution is to conduct imagery rehearsal therapy in a guided self-help format. In the current study, 70 participants with nightmares according to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders were randomized to either telephone-guided imagery rehearsal therapy (n = 36) or a wait-list condition (n = 34). Participants in the imagery rehearsal therapy condition received three sessions over the course of 5 weeks. Every treatment session was followed by telephone support delivered by postgraduate students. Participants who received imagery rehearsal therapy showed larger improvements on nightmare frequency (d = 1.03; p < .05), nightmare distress (d = 0.75; p < .05) and insomnia severity (d = 1.12; p < .001) compared with the participants in the wait-list condition. The effects were sustained at 3- and 6-month follow-up. No significant effects were observed on the number of nights with nightmares per week, anxiety and depression. In line with earlier reports, the treatment effect was mediated by the increase of mastery at mid-treatment, underlining the mechanistic value of mastery in imagery rehearsal therapy. The present study demonstrates that it is possible to deliver imagery rehearsal therapy in a self-help format supported by unexperienced therapists and with relatively little time investment. This opens possibilities in terms of cost-effectiveness, scalability and dissemination of imagery rehearsal therapy in the treatment of nightmares.