The effects of cognitive behavioral therapy as an anti-depressive treatment is falling: A meta-analysis.A meta-analysis examining temporal changes (time trends) in the effects of cognitive behavioral therapy (CBT) as a treatment for unipolar depression was conducted. 
Meta-analysis
A comprehensive search of psychotherapy trials yielded 70 eligible studies from 1977 to 2014. 
Psychotherapy trials
Effect sizes (ES) were quantified as Hedge's g based on the Beck Depression Inventory (BDI) and the Hamilton Rating Scale for Depression (HRSD). 
Beck Depression Inventory (BDI)
Effect sizes (ES) were quantified as Hedge's g based on the Beck Depression Inventory (BDI) and the Hamilton Rating Scale for Depression (HRSD). 
Hamilton Rating Scale for Depression (HRSD)