Background: Increasing access to treatment via smartphone apps is an important topic in Social Anxiety Disorder (SAD). ‘Challenger’ is an app promoting exposure exercises in daily life. The present study evaluated the additional benefit of using the app as adjunct to Internet-based unguided self-help for SAD. In a second step, we also tested how the app and the self-help programme (SH) should best be combined.

Method: 209 patients diagnosed with SAD were randomly allocated to three groups. Group 1 received the app and the self-help programme for six weeks (parallel treatment), group 2 first received SH for six weeks and then the app for six weeks (sequential treatment). Group 3 was a wait-list group. Comparisons were made at week 7 evaluating the potential add-on effect of the app (SH plus app versus SH only) and at week 14 comparing the parallel to the sequential treatment. Participants filled in questionnaires prior, during, and post treatment, and at 4- and 12- months follow-up.

Results: Intention-to-treat analyses showed no significant effect of adding the app to Internet-based self-help. However, among participants actively using the app, adding Challenger to self-help resulted in significantly less social anxiety (d = 0.30). At week 14, decreases in social anxiety were large for both the parallel and the sequential group with no differences between the active groups (dwithin = 1.12–1.19). Changes were maintained throughout the follow-up period.

Conclusion: Results of the current study cautiously support the notion of adding a smartphone app to unguided self-help for SAD. Future studies should investigate how patients can be motivated to use the app more frequently.

Internet-based cognitive behavior therapy (ICBT) and self-help books have proven to be effective treatments for social anxiety. These treatments can increase the opportunity for more people to access evidence-based psychological treatment. More knowledge of the factors that predict treatment outcomes is needed for individuals to get the right type of treatment. The purpose of this study was to investigate if education level, recruitment mechanism, or previous psychological or psychopharmacological treatment predicts successful treatment outcomes in conjunction with self-help treatment for social anxiety disorder (with or without elements of ICBT). Two treatment groups (n = 138) underwent a six-week self-help treatment. Treatment for one of the groups included a mobile application. Measurements using the Liebowitz So-cial Anxiety Scale Self-Report as the main outcome measure were taken before, during, and in connection with the completion of treatment. Recruitment via DN was associated with higher odds of a successful treatment outcome (OR = 4.1) compared to recruitment via Facebook. Similarly, absence of previous psychological treatment was associated with higher odds of a successful treatment outcome (OR = 4.4).