The purpose of the study is to compare the efficacy of a physiologically-augmented breath-focused mindfulness-based intervention to reduce symptoms of dissociation that are associated with psychological trauma, as well as symptoms of posttraumatic stress disorder (PTSD). The study will evaluate whether physiological augmentation produces a greater change in dissociative symptoms, meditative engagement and attentional control, compared to non-augmented mindfulness. The augmentation comprises physiological feedback in the form of a vibration on the wrist. Vibrations are delivered by a device that will be placed on a participant's arm; the device vibrates in proportion to the person's breath.