PE-PC consists of four weekly 30-minute sessions. At the 4th session or 9-week assessment point (whichever comes first), early responders will step down to every-other-week sessions for the duration of the second stage (for 8 weeks).

During the first stage of treatment, participants will receive four weekly clinician support sessions or 9 weeks (whichever occurs first). Early responders will be encouraged to continue app use but will discontinue clinician support sessions for the remaining 8 weeks.

PE-PC consists of four weekly 30-minute sessions. At the 4th session or 9-week assessment point (whichever comes first), slow responders that are then randomized to full PE and will have sessions once a week for eight weeks. During these 60-minute sessions, participants will practice in vivo and imaginal exposure and continue these exposure exercises every day at home.

During the first stage of treatment, participants will receive four weekly clinician support sessions or 9 weeks (whichever occurs first), slow responders that are then randomized to full PE will have sessions once a week for eight weeks. During these 60 minute sessions, participants will practice in vivo and imaginal exposure and continue these exposure exercises every day at home.

Treatment follows the standardized PE-PC manual and workbook.PE-PC consists of four weekly 30-minute sessions. In vivo and imaginal exposure are introduced at the first session and reviewed at Sessions 2-4. To conduct in vivo exposure, participants repeatedly and systematically approach objectively safe people, places, objects, and situations that they avoid because these stimuli remind them of their trauma. At the 4th session or 9-week assessment point (whichever comes first), early responders will step down to every-other-week sessions for the duration of the second stage.

The CAPS-5 is a clinician-rated PTSD rating scale consisting of 30 items; the total score is calculated as the sum of 20 items assessing the 20 DSM-5 PTSD symptoms. These symptom items are scored on a 5-point scale from 0 (absent) to 4 (extreme/incapacitating). The total score of the 20 items ranges from 0 to 80 with higher scores indicating more severe PTSD symptoms. Therefore, a decrease in the total score indicates symptom improvement.

The PTSD Checklist for DSM-5 (PCL-5) is a 20-item self-report measure that assesses symptoms of PTSD. The PCL-5 has a variety of purposes, including monitoring symptom change during and after treatment. The minimum score is 0, the maximum is 80 (higher scores indicate increased PTSD severity).