Dissonance induction and reduction: a possible principle and connectionist mechanism for why therapies are effective.

Several empirically supported treatments for depression are currently available with little understanding of either principles or mechanisms that are responsible for their effectiveness. This article reviews existing principles and finds that they contain little mechanism information. A connectionist mechanism used to explain why systematic desensitization and response prevention are effective in treating anxiety disorders is reviewed and generalized to understand why empirically supported treatments of depression work. This mechanism suggests a dissonance induction followed by reduction principle that can guide clinical practice. Application is extended to learned helplessness and rumination because they are associated with depression. Implications for clinical practice are provided. Limitations are identified and discussed.