Psychological Medicine

Original Articles

Long-term efficacy of Internet-based cognitive behavior therapy for obsessive–compulsive disorder with or without booster: a randomized controlled trial

E. Anderssona1 c1, S. Stenebya1, K. Karlssona1, B. Ljótssona2, E. Hedmana2a3, J. Enandera1, V. Kaldoa1, G. Anderssona1a4, N. Lindeforsa1 and C. Rücka1

a1 Department of Clinical Neuroscience, Division of Psychiatry, Karolinska Institutet, Stockholm, Sweden

a2 Department of Clinical Neuroscience, Division of Psychology, Karolinska Institutet, Stockholm, Sweden

a3 Osher Center for Integrative Medicine, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden

a4 Department of Behavioral Sciences and Learning, Swedish Institute for Disability Research, Linköping University, Linköping, Sweden


Background As relapse after completed cognitive behavior therapy (CBT) for obsessive–compulsive disorder (OCD) is common, many treatment protocols include booster programs to improve the long-term effects. However, the effects of booster programs are not well studied. In this study, we investigated the long-term efficacy of Internet-based CBT (ICBT) with therapist support for OCD with or without an Internet-based booster program.

Method A total of 101 participants were included in the long-term follow-up analysis of ICBT. Of these, 93 were randomized to a booster program or no booster program. Outcome assessments were collected at 4, 7, 12 and 24 months after receiving ICBT.

Results The entire sample had sustained long-term effects from pre-treatment to all follow-up assessments, with large within-group effect sizes (Cohen's d = 1.58–2.09). The booster group had a significant mean reduction in OCD symptoms compared to the control condition from booster baseline (4 months) to 7 months, but not at 12 or 24 months. Participants in the booster group improved significantly in terms of general functioning at 7, 12 and 24 months, and had fewer relapses. Kaplan–Meier analysis also indicated a significantly slower relapse rate in the booster group.

Conclusions The results suggest that ICBT has sustained long-term effects and that adding an Internet-based booster program can further improve long-term outcome and prevent relapse for some OCD patients.

(Received October 26 2013)

(Revised January 30 2014)

(Accepted February 07 2014)

(Online publication March 14 2014)

Key words

  • Cognitive behavior therapy;
  • booster;
  • Internet;
  • long-term outcome;
  • obsessive–compulsive disorder;
  • relapse prevention


c1 Address for correspondence: E. Andersson, M.Sc., M 46, Karolinska University Hospital, Huddinge, SE-141 86 Stockholm, Sweden. (Email: