Individuals who experience potentially traumatic events might develop long-lasting mental health problems. Limitations to health care resources, particularly in the context of mass disasters, indicate that self-help interventions could serve as important complementary offers to people in need.

The aim of this study is to evaluate whether the Swedish version of the Swedish version of the PTSD Coach self-help smartphone application can reduce levels of posttraumatic stress and related difficulties. The study is a randomized controlled trial in which participants' levels of posttraumatic stress and related difficulties after three months use of PTSD Coach will be compared to a waitlist condition. Additionally, in order to better understand the interplay between app use and health status, participants in both groups will receive text messages in which they are asked to respond to a small number of very brief questions about specific behaviors and current health status for three weeks during the intervention period.

A majority of humans experience a potentially traumatic event during their lifetime, and many experience more than one. These events are of overwhelming emotional nature and have the capacity to evoke intensive distress. For many people, the distress dissipates either spontaneously or with the help from professional supports over the course of a couple of weeks. However, a substantial minority of people go on to develop significant levels of posttraumatic stress.

Chronic posttraumatic stress is often experienced together with clinical levels of other forms of psychopathology such as depression or anxiety disorders and the chronic condition can become debilitating over many years. There are effective interventions, however, they are as of yet difficult to access.

An uncontrolled pilot study of the Swedish PTSD Coach smartphone app indicated favorable outcomes and feasibility of the intervention (Cernvall, Sveen, Johannesson, & Arnberg, 2018). The app includes four modules: psychoeducation, rating and monitoring of distress, information about help and support, and strategies to cope with distress. The app is designed to be used with or without internet connection and uses little space on the smartphone.

This study will investigate whether the Swedish version of the PTSD Coach self-help smartphone application is beneficial for people who experience elevated levels of posttraumatic stress after a potentially traumatic event. The study is a randomized controlled trial with two conditions. In the intervention condition, participants are allowed free use of the PTSD Coach smartphone app. The control group is a waitlist condition. The intervention will take place during three months and is powered to detect a between-group effect size at the post-intervention assessment of d=0.5.

This study will also use an intensive longitudinal data collection method within the intervention period in order to better understand the interplay between app use and health status. Participants in both groups will receive text messages in which they are asked to respond to six very brief questions about specific behaviors and current health status for three weeks during the intervention period.

After the intervention period, participants across groups will be compared on a number of outcome variables related to posttraumatic stress, other mental health issues, daily function, and measures on healthcare consumption. The participants in the waitlist group will then be given access to the PTSD Coach app and both groups will be followed for two additional assessments after six and nine months.

Inclusion Criteria:

• Age ≥ 18 years
• Adequate Swedish language comprehension
• Experienced a potentially traumatic event according to DSM-5 PTSD Criterion A during the past 2 years
• At least mild forms of posttraumatic stress, i.e., PCL-5 total score ≥ 10
• Access to smartphone able to run PTSD Coach app

Exclusion Criteria:

• Positive screening for bipolar disorder, psychotic disorder, ongoing substance disorder, or severe suicidality according to Mini International Neuropsychiatric Interview version 7.0.0
• current or planned psychological treatment within next three months
• current use of medication that may influence psychological treatment
• change in medication in the past months or planned changes within next three months
• ongoing potential traumatic context (e.g., ongoing domestic violence)

All collected IPD