Circadian Influence on Prolonged Exposure Therapy for PTSD

Proposed research will examine time-of-day effects on trauma-related fear extinction using PE therapy for PTSD in the National Center for PTSD (NCPTSD). The primary mechanistic outcome measure will be change in SDI-PR; a secondary mechanistic outcome will be session-to-session reduction in peak SUDS ratings to imaginal exposures. The primary clinical outcome will be change in CAPS-5 severity score; a secondary clinical outcome will be session-to-session reduction in self-reported PTSD symptoms (PCL-5). Participants meeting inclusion criteria (described below) will be randomized to either PE sessions that begin from 07:00 to a time no later than 2 hours past a participant's customary rise time, or to the last treatment session of the day beginning at 16:00 or later. Participants will complete daily at-home imaginal-exposure homework within the same time frame as their PE sessions are scheduled (i.e., within 2 hours of awakening for morning group and between 16:00 and 2 hours before bedtime for late afternoon group). The assessment schedule will be identical for all participants. Participants who meet study inclusion criteria at screening will first begin a 7-day, pre-study sleep-monitoring period with wrist actigraphy, sleep diaries and completion of a diurnal profile of salivary cortisol levels. Trauma-related fear will be assessed using the standard SDI procedures detailed below at pre-treatment, after 5 PE sessions (mid-treatment), and after all 10 PE sessions (post-treatment). The CAPS-5 will be administered at these same times. PCL-5 measurements will be obtained at each treatment session and SUDs will be obtained during all treatment sessions that include imaginal exposure (sessions 3-8). All SDI sessions will be carried out at a standardized time of day in the late-afternoon (15:00-17:00). PE treatment will be administered at a targeted rate of once per week. At each PE and assessment session, pre-session saliva samples will be obtained for cortisol measurement and normalized using the diurnal profile of cortisol obtained during the sleep-assessment week. Participants will wear the wrist actigraph and complete sleep diaries throughout PE. The diurnal cortisol profile will be repeated at the post-treatment assessment.