RecruitingDevice studyA Study of a Novel EEG Neurofeedback System for PTSD TreatmentThe goal of this clinical trial is to learn if training with the Prism system can reduce PTSD symptoms in US military Veterans and civilians with PTSD. Prism is a form of neurofeedback training that uses EEG signals to promote self-regulation of brain function. The main question this study aims to answer is: Does Prism training lead to decreased PTSD symptoms in US Veterans and civilians when used in addition to usual PTSD treatment? Researchers will compare Prism training to a sham training (a look-alike training that does not provide real feedback on brain activity) to see if Prism training decreases PTSD symptoms. Participants will: * Complete two one-hour in-person training sessions a week for about 8 weeks (15 sessions) * Complete two booster training sessions one month and two months after finishing the main training course * Participate in three detailed interviews: one before training, a second after nine weeks of training, and a third one month after the last booster training session (about 20 weeks after the initial visit)