(PSYCHIATRIC TIMES) - The substantial and often recurrent distress and impairment associated with major depressive disorder (MDD) in youth has prompted increased interest in the identification and dissemination of effective treatment models. Evidence supports the use of several antidepressant medications, specific psychotherapies, and, in the largest treatment study of depressed teenagers, the combination of fluoxetine and cognitive-behavioral therapy (CBT) as effective treatments.1-3 CBT is the most extensively tested psychosocial treatment for MDD in youth, with evidence from reviews and meta-analyses that supports its effectiveness in that population.3-5
CBT is a time-limited, problem- focused intervention that seeks to reduce emotional distress through the modification of maladaptive beliefs, assumptions, attitudes, and behaviors.6 As outlined by Lewinsohn and Clarke,7 different CBT interventions emphasize different techniques to effect change, with some interventions primarily targeting cognitive factors and others primarily targeting behavioral factors. Reflecting this distinction, there have been 2 major theoretical approaches to CBT with adolescents.
The first approach, identified with the cognitive therapy of Beck and his colleagues,8 is based on a model in which cognitive processes are seen as the major maintaining variables associated with MDD. In Beck's model, the task of the therapist is to enhance the patient's ability to monitor mood; identify connections between mood and cognition; and identify, challenge, and modify automatic thoughts, assumptions, and core beliefs that sustain MDD. This model has been adapted by Brent and colleagues9 for treating adolescents.
The second approach is more behavioral and multifactorial. Associated with Lewinsohn and colleagues,10 this approach has been used with adults and adolescents and is based on the assumptions that behavior and thoughts sustain depressed mood, and that either behavioral or cognitive change can serve as the engine of therapeutic progress.
Despite different areas of emphasis, both of the major CBT approaches posit that cognitive factors such as cognitive distortions, negative automatic thoughts, dysfunctional attitudes, negative attributional style, and hopelessness play a major role in the onset and maintenance of depressive symptoms.6 However, the specific cognitive processes through which CBT works to counter MDD in young people are not well understood. Understanding treatment mechanisms is of both theoretical and practical importance. A clear understanding of therapeutic mechanisms would allow psychosocial treatment developers to focus on the intervention components that are most effective, thereby promoting amplification of the more active components and reduction or removal of the less active elements. In addition, a review by Kazdin and Nock11 proposes that studying mechanisms of therapeutic change can assist the adoption of effective treatments by practicing clinicians.
In this article we focus on cognitive factors that have been shown to influence the effectiveness of CBT for adolescent MDD. We identify factors that affect CBT treatment outcomes by examining 3 types of variables: predictors, moderators, and mediators. Predictors are variables present before treatment that influence treatment outcomes across all treatment conditions. For example, if, in a comparison of CBT and a different psychotherapy for MDD, adolescents with high levels of hopelessness had worse outcomes across both conditions, then hopelessness would be considered a predictor.
Moderators are pretreatment factors that interact with the treatment conditions to predict treatment outcome, and thereby represent factors that predict a differential response to CBT. For example, if adolescents with high levels of hopelessness had better outcomes with CBT than with an alternative psychotherapy, hopelessness would be a moderator. Mediators are factors that account for or explain the process of therapeutic change during CBT. For example, if it were shown that CBT treatment outcomes were attributable to a reduction in hopelessness during treatment, then hopelessness would be a mediator.
Mediational analyses are those that are most valuable in highlighting processes of change associated with effective treatment. The evaluation of mediators can help address the following 3 questions, which have been explored in the literature on adults with MDD and are only beginning to be studied in adolescents with MDD. First, does CBT lead to changes in cognition associated with MDD? Second, if CBT leads to cognitive change, does the cognitive change lead to a reduction in symptoms of MDD? Third, is change in depressive cognitions unique to CBT, or is it associated with other effective treatments for MDD? In this article, we explore the first 2 questions with reference to studies of CBT that emphasize cognition, studies of multifactorial CBT, and the largest treatment study of CBT for adolescent MDD to date.
Of note, most clinical trials are sufficiently powered to test their main hypotheses, which pertain to outcome, and to identify predictors. By contrast, most trials are not sufficiently powered to test adequately for moderators or mediators. Therefore, most analyses for moderators or mediators must be considered exploratory.
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