gms | German Medical Science

Background: Evidence-based treatments for Major Depressive Disorder (MDD) are not very successful in improving functional and health outcomes. Attention has increasingly been focused on the prevention of MDD. Psychological interventions for the prevention of depression might also be a cost-effective way to reduce the burden associated with depressive disorders.

Objective: The aim of the study was to evaluate the (cost-) effectiveness of a web-based guided self-help intervention to prevent MDD in people with subthreshold depression.

Methods: We conducted a pragmatic randomised controlled trial with follow-up at 12 months. Participants were recruited from the general population via a large statutory health insurance company and an open access website. All participants had unrestricted access to care-as-usual (i.e. visits to the GP) and were randomized to either a web-based guided self-help intervention (i.e. cognitive-behavioural and problem-solving therapy supported by an online trainer; n = 202) or web-based psycho-education (n = 204). The primary outcome was time to onset of MDD in the intervention relative to the control group over the 12-month follow-up period as assessed by blind diagnostic raters using the telephone-administered structured clinical interview for DSM-IV Axis Disorders (SCID) at 6- and 12-month follow-up covering the period to the previous assessment. Depression-free years (DFYs) were assessed based on the SCID interviews. Costs were self-assessed through a questionnaire and were related to DFYs and quality-adjusted life years (QALYs) from a public health care and societal perspective.

Results: Among 406 randomized participants (mean age, 45 years; 73.9%women), 335 (82%) completed the telephone follow-up at 12 months. Fifty-five participants (27%) in the intervention group experienced MDD compared with 84 participants (41%) in the control group. Cox regression analyses controlling for baseline depressive symptom severity revealed a hazard ratio of 0.59 (95%CI, 0.42-0.82; P = .002) at 12-month follow-up. The number needed to treat (NNT) to avoid 1 new case of MDD was 5.9 (95%CI, 3.9-14.6). Significantly more DFYs were gained in the intervention group (0∙82 vs 0∙70). Likewise, QALY health gains were in favour of the intervention. Assuming a willingness-to-pay of €20,000, the intervention’s likelihood of being cost-effective was 99% from both perspectives for gaining a DFY and 60% (health care perspective) and 64% (societal perspective) for gaining a QALY.

Discussion: The NNT of 5.9 found in the present study is comparable with NNTs from studies of the treatment of MDD. It implies that of those patients identified with subthreshold depression and participating in the intervention, almost 17% would benefit in terms of a prevented episode of MDD within a 12-month period. Our study underlines the potential of web-based treatments for subthreshold depression and adds that this may not only restore health in people with subthreshold depression, but in addition reduces the risk of developing a MDD.

Practical implications: Offering the intervention has an acceptable likelihood of being more cost-effective than enhanced usual care and could therefore reach community members on a wider scale. The web-based intervention has been implemented by a large German statutory health insurance scheme. The intervention is the first evaluated prevention program in Germany that is proven to be effective in preventing the onset of depression. Pre-post between-group effect sizes found in the randomised controlled trial have been compared with routinely collected data after implementation. No significant differences have been found.