Participants will first undergo an evaluation session that will include an interview (Immediate Stress Reaction Checklist) and questionnaires. Participants will subsequently be randomly assigned to receive either modified prolonged exposure therapy or attention control, starting the assigned intervention immediately. Participants in each arm will receive three weekly treatment sessions. Treatment will involve psychoeducation about common reactions to trauma, imaginal exposure (revisiting memories of a recent trauma out loud with a therapist and audio-recording these for review at home), exposure in vivo and breathing retraining. All participants will undergo assessments 2, 6 (primary endpoint) and 12 months after the intervention by blinded assessors. Patients unable to come to the clinic for follow-up assessments will be interviewed via telephone or skype. Source data will be quality monitored by an independent party (Karolinska trial alliance) according to the Helsinki Declaration.