Background
Psychological interventions have a central role in the treatment of depressive disorders as an alternative to or a combination with antidepressant drugs. A variety of therapies have been developed based on cognitive-behavioural, interpersonal, psychodynamic, or humanistic approaches. A recent large network meta-analysis of 198 randomized trials in patients with depression found that while the amount and the robustness of evidence varied across the single therapies the clinical effects seemed to be similar in size. Most of the trials included in this large meta-analysis were performed in specialized mental health care settings. In relation to treatment of depression in primary care two main questions arise. First, can we extrapolate the findings from trials in specialized settings to primary care? Patients with depression in primary care sometimes have less severe and more somatic symptoms than patients referred to specialty mental health care. Second, the limited number and the regional distribution of qualified professionals make it difficult to provide personalized multi-session face-to-face psychological therapies on a population-wide level. Therefore, a number of interventions have been developed in which the contact time with health care professionals is reduced and/or in which the treatment is delivered by telephone, electronically, or by using printed materials. It is crucial to know how these less resource intensive methods of providing psychological treatments compare to the more intense "traditional" interventions.
We recently reported a systematic review and meta-analysis of 30 randomized trials comparing psychological treatments with usual care or placebo controls in depressed primary care patients. Psychological treatments were superior to usual care. Effects of telephone- or internet-based and of reduced minimal contact cognitive behavioural approaches were broadly similar to those of personalized therapies. However, as trials had to include a usual care or placebo control group in that analysis, we excluded trials and contrasts comparing active treatments (psychological therapy, pharmacotherapy, or combination of both) with each other. Furthermore, indirect comparison of effect sizes derived from conventional meta-analyses of trials with usual care controls is methodologically problematic. Network meta-analysis provides an approach to estimate effect sizes for all possible pairwise comparisons whether or not they have been compared head to head in trials making efficient use of all available evidence. Thus, in the current study we utilized considerably more data than in our previous review and made use of the method of network meta-analysis in order to estimate the comparative effectiveness of psychological treatments formally. By doing so, we were not only able to increase the precision of our previous estimates on comparisons with control treatments but also to provide effect size estimates for all pairwise comparisons and to test whether the evidence base is consistent (i.e., whether pieces of information from various sources such as direct and indirect comparisons agree with each other). Correspondingly, amending our previous dataset with head to head comparisons, here we report a network meta-analysis of randomized trials in primary care patients with depression to compare the effectiveness of psychological treatments grouped by theoretical background, intensity of contact with the health care professional, and delivery mode.