Background and aimsPsychodynamic psychotherapy (PDT) is an effective treatment for major depressive disorder (MDD), but not all clients with MDD can receive psychotherapy. Using the Internet to provide psychodynamic treatments is one way of improving access to psychological treatments for MDD. The aim of this randomised controlled trial was to investigate the efficacy of an Internet-based psychodynamic guided self-help treatment for MDD.MethodsNinety-two participants who were diagnosed with MDD according to the Mini-International Neuropsychiatric Interview were randomised to treatment or an active control. The treatment consisted of nine treatment modules based on psychodynamic principles with online therapist contact. The active control condition was a structured support intervention and contained psychoeducation and scheduled weekly contacts online. Both interventions lasted for 10 weeks. The primary outcome measure was the Beck Depression Inventory-II (BDI-II).ResultsMixed-effects model analyses of all randomised participants showed that participants receiving Internet-based PDT made large and superior improvements compared with the active control group on the BDI-II (between-group Cohen's d = 1.11). Treatment effects were maintained at a 10-month follow-up.ConclusionsInternet-based psychodynamic guided self-help is an efficacious treatment for MDD that has the potential to increase accessibility and availability of PDT for MDD.Trial RegistrationClinicaltrials.gov: NCT01324050

Little is known about the individual factors that predict outcomes in Internet-administered psychological treatments. We hypothesized that greater cognitive flexibility (i.e. the ability to simultaneously consider several concepts and tasks and switch effortlessly between them in response to changes in environmental contingencies) would provide a better foundation for learning and employing the cognitive restructuring techniques taught and exercised in therapy, leading to greater treatment gains. Participants in three trials featuring Internet-administered psychological treatments for depression (n = 36), social anxiety disorder (n = 115) and tinnitus (n = 53) completed the 64-card Wisconsin Card Sorting Test (WCST) prior to treatment. We found no significant associations between perseverative errors on the WCST and treatment gains in any group. We also found low accuracy in the classification of treatment responders. We conclude that lower cognitive flexibility, as captured by perseverative errors on the WCST, should not impede successful outcomes in Internet-delivered psychological treatments.