Cognitive-Behavioral Therapy for Adolescent Depression
Processes of Cognitive Change

Multifactorial CBT
A second stream of research has been built on Lewinsohn's multifactorial model of MDD, which identifies multiple behavioral, cognitive,and biological factors that contribute to MDD.¹⁰ To simultaneously address these factors, Clarke and colleagues¹⁸ designed the Adolescent Coping With Depression Course (CWD-A), a course of CBT that is group-administered, psychoeducational, and skills-oriented in nature.

Two randomized trials have assessed the effectiveness of the CWD-A group CBT intervention compared with CWD-A plus a weekly parent psychoeducation group and a wait-list control.^10,19 The first study involved 59 adolescents who met diagnostic criteria for MDD or intermittent depression, whereas the second study involved 96 adolescents who met diagnostic criteria for MDD or dysthymia. Both of these trials found that rates of recovery, as defined by no longer meeting criteria for initial diagnosis, were greater in the 2 CBT conditions than in the wait-list group. Across both studies, higher levels of rational (nondepressive) thinking at baseline, as measured by the Subjective Probability Questionnaire (R. Munoz and P. Lewinsohn, unpublished data, 1976), were a predictor of better treatment outcomes. No analyses of moderators or mediators were reported in these trials.

A recent application of the CWD-A compared it with a life skills condition for adolescents with comorbid MDD and conduct disorder.²⁰ Adolescents treated with CWD-A had higher recovery rates than those treated with the life skills condition (39% vs 19%). In the context of this controlled trial, the cognitive variables of hopelessness, negative automatic thoughts, and dysfunctional attitudes were assessed. Over the 1-year follow-up, lower levels of hopelessness and negative thoughts, but not dysfunctional attitudes, were found to predict faster recovery.²¹ In analyses of this trial, potential mediators of treatment outcome were explored in adolescents who received CBT intervention.²² One of the cognitive factors, automatic negative cognitions, which was measured with the Automatic Thoughts Questionnaire developed by Hollon and Kendall,²³ mediated the effects of CBT on depression outcomes. None of the other variables that were tested (dysfunctional attitudes, relaxation, social skills, pleasant activities, or problem-solving) fulfilled the criteria for mediation of treatment effects. This finding suggests that reducing negative thinking may be the primary mechanism through which this form of CBT reduces depression among youths with conduct disorder and depression.

Another notable finding was that reducing negative thinking significantly reduced symptoms of depression, even though CBT did not appear to have an impact on underlying dysfunctional attitudes, as measured by the Dysfunctional Attitude Scale.²⁴ Counter to the findings of the cognitive bibliotherapy trial, these findings suggest that it may not be necessary for the clinician to engage in depth-oriented cognitive techniques for this form of CBT to be effective.¹⁷

Taken together, results of the second stream of research provide evidence that CBT is associated with change in a specific cognitive factor (automatic negative thoughts) and that this change accounts for the effect of CBT on adolescent outcomes. Results of this stream of research are consistent with the results of 2 prevention studies for adult depression that found that measures of negative thoughts were the strongest mediators of reductions in depressive symptoms following treatment with CBT.

In the first study, Munoz and colleagues²⁵ randomly assigned 150 predominantly minority, low-income primary care patients to an experimental CBT condition or 1 of 2 control conditions: information only or no treatment. At posttreatment and 6-month follow-up, reduction in depressive symptoms was significantly mediated by a reduction in negative thoughts, while at the 12-month follow-up, reduction was mediated by reduced negative thoughts and increased optimism.

In the second study, Allart-van Dam and colleagues²⁶ randomized adults at risk for developing MDD to the Coping With Depression CBT course or an assessment and advice only condition. One month after acute treatment, negative automatic thoughts and self-esteem were found to mediate a reduction in symptoms of MDD. By contrast, measures of the frequency of interpersonal behavior and pleasant events were not found to mediate the results of CBT, which provided further indication that change in cognition may be the most important mechanism of change.

A large adolescent treatment study
The Treatment of Adolescents With Depression Study (TADS)[2] represents the largest treatment study of adolescents with MDD to date. Before TADS, a critical limitation of CBT research was its isolation from developments in pharmacotherapy research.¹ TADS was therefore designed to compare CBT, fluoxetine, and their combination as treatments for moderate to severe MDD in adolescents.² Response rates for CBT and medication in earlier studies were about 50% to 60%, indicating considerable room for improvement in treatment outcomes. A primary hypothesis of TADS was that the combination of CBT and fluoxetine would be more effective than either therapy alone.

In TADS, 439 adolescents with moderate to severe MDD were randomly assigned to receive CBT, fluoxetine, a CBT and fluoxetine combination, or clinical management with a pill placebo for 12 weeks. The CBT used in TADS combined the 2 streams of American CBT for adolescents: skills training from the Lewinsohn model was embedded in individual psychotherapy sessions that followed a structure from the Beck model. (The TADS CBT model has been described by Rohde and colleagues.²⁷)

Acute treatment results supported combination treatment as the most effective intervention, as measured by rate of change of scores on the Children's Depression Rating Scale-Revised assessed by an independent evaluator uninformed of treatment assignment.^28,29 Fluoxetine, but not CBT, was also superior to placebo at the end of 12 weeks of treatment. A secondary analysis indicated superiority of combination treatment on speed of response rated by treating clinicians.³⁰

The TADS team explored possible predictors or moderators of acute treatment outcome, based on a literature review of previous studies of psychotherapy or pharmacotherapy for childhood or adolescent internalizing disorders (anxiety or depression).³¹ Two of these were cognitive variables. One of these, hopelessness, proved to be a predictor of acute outcome. Lower levels of hopelessness at baseline predicted more favorable response to treatment than did higher levels of hopelessness, regardless of treatment arm.

A second cognitive variable was a moderator of acute outcome: cognitive distortion. Among adolescents with higher levels of cognitive distortion, the addition of CBT to fluoxetine led to improved results. By contrast, the addition of CBT to fluoxetine did not improve treatment outcome in those with lower levels of distortion. As noted by Curry and colleagues,³¹ one potential interpretation of these results is that CBT addresses a vulnerability to depressogenic thinking, but that its benefits for moderately to severely depressed adolescents are only evident in the short term when combined with fluoxetine.

A recent secondary analysis of the TADS trial compared the rate of cognitive change across the 12 weeks of treatment for each of the following conditions: combination, fluoxetine, CBT, and placebo.³² Cognitive change was measured using factor analytically derived scores representing cognitive distortions, cognitive avoidance, and solution-focused thinking, based on a previous analysis by Ginsburg and colleagues.³³ Combination treatment led to a significantly greater rate of reduction in cognitive distortions and avoidance than did other conditions. Thus, when analyzing data with factor-derived scores, the pattern of cognitive change paralleled that for change in depression.

Analysis of treatment mediators in TADS is currently under way. In addition, more detailed analyses of specific cognitive variables including negative automatic thoughts, dysfunctional attitudes, and attributional style will track changes in these processes across the different treatments.

Summary
Cognitive variables that predict favorable treatment outcomes in adolescents with depression include higher levels of rational thoughts, less hopelessness, fewer negative thoughts, and fewer cognitive distortions at baseline.^10,14,22 In an analysis of TADS data, cognitive distortions at baseline were also shown to moderate the effects of combined CBT and fluoxetine, such that adolescents with high levels of cognitive distortion were more likely to experience incremental benefits from CBT as part of combination treatment.³¹ In an analysis of the Brent study, hopelessness was found to mediate the predictive effects of referral source on outcome across 3 types of psychotherapy.¹⁴

The only variables that have been found to mediate the results of CBT specifically are negative automatic thoughts, and in a small subclinical sample, dysfunctional attitudes, which suggests that a reduction in these variables may be important mechanisms of change in CBT.^17,23 Mediational analyses have not yet been conducted on the TADS data, which precludes conclusions about the mechanisms of change in pharmacological and combination treatments. Further research is needed to uncover the specific strategies used in therapy that reframe negative cognition, modify dysfunctional beliefs, and improve depressive symptoms.