A 35-year-old male veteran with PTSD reports severe, recurrent trauma-related nightmares that wake him multiple times per night and cause significant daytime fatigue and hyperarousal. He is currently taking sertraline 200 mg daily, which has improved his daytime anxiety and avoidance symptoms but has not reduced the nightmares. The PMHNP considers adding prazosin. Which of the following best describes the rationale for prazosin in this clinical scenario?