Depression is among the most prevalent disorders worldwide. In view of numerous treatment barriers, internet-based interventions are increasingly adopted to "treat the untreated". The present trial (registered as NCT01401296) was conducted over the internet and aimed to assess the efficacy of an online self-help program for depression (Deprexis). In random order, participants with elevated depression symptoms received program access or were allocated to a wait-list control condition. After eight weeks, participants were invited to take part in an online re-assessment. To compensate for common problems of online studies, such as low completion rates and unclear diagnostic status, reminders and incentives were used, and clinical diagnoses were externally confirmed in a subgroup of 29% of participants. Relative to the wait-list group, program users experienced significant symptom decline on the Beck Depression Inventory (BDI; primary outcome), the Dysfunctional Attitudes Scale (DAS), the Quality of Life scale (WHOQOL-BREF) and the Rosenberg Self-Esteem Scale (RSE). Compared to wait-list participants, symptom decline was especially pronounced among those with moderate symptoms at baseline as well as those not currently consulting a therapist. Completion (82%) and re-test reliability of the instruments (r = .72-.87) were good. The results of this trial suggest that online treatment can be beneficial for people with depression, particularly for those with moderate symptoms.
