Orexin-receptor antagonist suvorexant to be evaluated for enhancing fear extinction in Veterans with **PTSD**

PTSD affects approximately 22% of Veterans, manifesting as re-experiencing, avoidance, negative thoughts, and hyperarousal. Current treatments primarily leverage fear extinction principles, involving repeated exposure to feared cues to diminish physiological reactions. However, these therapies often have limited efficacy for many. Orexin, a wake-promoting neuropeptide, is known to modulate stress responses and has been suggested to enhance fear extinction. Targeting the orexin system presents a novel therapeutic avenue to improve PTSD outcomes by directly influencing this critical recovery process.

This proposed study will examine whether suvorexant, a selective orexin-receptor antagonist, enhances fear extinction in Veterans diagnosed with PTSD and co-occurring insomnia. The primary objective is to assess suvorexant's impact on fear extinction, a core mechanism underlying recovery from PTSD. Secondary objectives include evaluating objective sleep improvements via wrist actigraphy and effects on PTSD-related nightmares using the Pittsburgh Sleep Quality Index-PTSD addendum (PSQI-A). Specific dosages, study duration, or participant numbers are not detailed.