A growing body of evidence suggests the significant efficacy of behavioral activation therapy (BA) for the treatment of depression, although BA had formerly been regarded as only a part of the techniques for cognitive-behavioral treatment (CBT). The aim of this article is to review the effectiveness, indications, and limitations of BA for the psychosocial treatment of depression. The research group of Washington University in St. Louis, who previously suggested the marked efficacy of BA based on component analysis of CBT, performed a large-scale study to compare the effect of BA and cognitive therapy (CT) or antidepressant medication on the acute phase of depression. As the results, BA was superior to CT and comparable to antidepressant medication in acute-phase treatment for a subgroup of patients with relatively severe depression. Moreover, a long-term follow-up study revealed a benefit of BA compared to pharmacological treatment in regard to the persistence of the effect and cost-effectiveness. More recently, a number of meta-analyses have indicated no significant difference among BA and other psychotherapies regarding their efficacy for the treatment of depression. Because BA does not require patients or therapists to learn complex skills and is also time-efficient, it is recommended as the first-line treatment for mild or moderate depression. However, further studies are needed to consider indications, the timing of induction, and variation in BA techniques if it is applied for the treatment of depression in a general clinical setting in Japan.
 <Authors' abstract>