ACTRN12616000956404.

Study name	Internet‐based intervention for posttraumatic stress disorder (PTSD) in soldiers: exploring mechanisms of treatment outcome.
Methods	Randomised controlled trial. Central randomisation by computer software using a random number generator.
Participants	Inclusion criteria Treatment group/wait list control group German‐speaking soldiers (active and out of duty) of the German Armed Forces PTSD Must have access to the Internet Healthy controls group German‐speaking soldiers of the German Armed Forces Experienced a potentially traumatic event or who have never experienced a potentially traumatic event Exclusion criteria Treatment group/wait list control group People with schizophrenia, schizotypal and delusional disorders (ICD‐10: F20‐F29) Suicidal patients People with acute manic episode People with acute substance abuse or dependence People receiving concurrent psychotherapeutic treatment Healthy controls group People fulfil criteria of PTSD or any other mental disorder
Interventions	Experimental arm Therapist‐guided Internet‐based intervention delivered via an online platform lasts 5 weeks and includes 10 structured writing assignments. Participants complete 2 assignments per week. Each assignment requires approximately 45 minutes of writing time. Comparator arm The wait list intervention group receives the same treatment as described above after an initial waiting period of 6 weeks. Participants in this group are seen for the initial assessment and pass through 1 additional assessment before the beginning of the treatment phase. The treatment procedure hereafter is identical to the protocol above.
Outcomes	Time point for assessment: post‐treatment, 3‐month follow‐up, 6‐month follow‐up, and 12‐month follow‐up Primary outcomes: PCL‐5, CAPS Secondary outcomes: PHQ, GAD‐7, SWLS, DERS, PTCI. PTGI, CSS
Starting date	22 August 2016
Contact information	Prof Christine Knaevelsrud Freie Universitaet Berlin christine.knaevelsrud@fu‐berlin.de
Notes	www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=370924