The temporal development of cognitive behavioral therapy as treatment for unipolar depression. An evaluation based on three meta-analyses, focusing on time-trends, effect sizes, and associated moderators

Abstract

The present thesis` main objective was to examine time-trends related to CBT as an anti-depressive treatment. A meta-analytic approach was the tool for such investigations, in which the formats of individual, group (GCBT), and mindfulness-based cognitive behavioral therapy (MCBT) were explored from a temporal point of view, and the results subsequently summarized in four articles. The meta-analyses measured the development of effect sizes (ES) with time. Potential moderator variables were also investigated. The primary outcome measure was the BDI, while the HDRS was utilized as a secondary outcome measure. The results revealed large ESs for all treatment formats, ranging from g = 0.80 to 1.89. A significant decline in treatment effects with time was observed across all statistical conditions for individual CBT, while GCBT showed a significant rise in ESs with the passing of time, based on the results from the primary outcome measure. For MCBT, there were found no trends related to the passing of time. Moderator analyses revealed that the fall in ES for CBT was more pronounced for trials where the original treatment manual had been utilized, while the rise in GCBT effect sizes was limited to trials were no specific treatment manual had been used (or reported). The conclusion is that CBT is efficient in all formats when it comes to battling depression. However, the results also point to the importance of continuous evaluations, updates or adaptations, in order to be in line with societal developments. This applies for treatment formats, manuals, and outcomes measures alike. Flexibility and frequent updating/adaptation are thus considered keywords to achieve the best possible treatment effects for CBT.