Although the effectiveness of cognitive behavioural therapy (CBT) in the management of panic disorder (PD) is now well established, there have been few studies of predictors of outcome with this patient group using clinical effectiveness trial data, a hypothesis-testing model, and a dependent measure of clinically significant change.

The data for this study came from a randomized controlled trial of three forms of CBT delivery for PD with and without agoraphobia (two 6-week CBT programmes, one of which was computer assisted, and one therapist-directed 12-week CBT programme), comprising a total of 186 patients across two sites. Based on previous related research, five hypothesized predictors of post-treatment and follow-up outcome were identified and examined, using a series of bivariate and multivariate analyses.

The results in general supported the hypotheses. Strength of blood/injury fears, age of initial onset of panic symptoms, co-morbid social anxieties and degree of agoraphobic avoidance were predictive of both measures of post-treatment outcome. Degree of residual social difficulties and the continued use of anxiolytics at post-treatment were also shown to predict poor outcome at the 6-month follow-up. However, strength of continuing dysfunctional agoraphobic cognitions by the end of active treatment did not predict outcome at follow-up for the sample as a whole.

The identification of consistent predictors of outcome with CBT has many clinical and research benefits. As CBT, however, is being delivered increasingly in a variety of brief formats, further research is required to identify moderators of response to these ‘non-standard’ treatment formats.

Despite the growth of reduced therapist-contact cognitive behavioural therapy (CBT) programmes, there have been few systematic attempts to determine prescriptive indicators for such programmes vis-à-vis more standard forms of CBT delivery. The present study aimed to address this in relation to brief (6-week) and standard (12-week) therapist-directed CBT for panic disorder (PD) with and without agoraphobia. Higher baseline levels of severity and associated disability/co-morbidity were hypothesized to moderate treatment effects, in favour of the 12-week programme.

Analyses were based on outcome data from two out of three treatment groups (n=72) from a recent trial of three forms of CBT delivery for PD. The dependent variables were a continuous composite panic/anxiety score and a measure of clinical significance. Treatment×predictor interactions were examined using multiple and logistic regression analyses.

As hypothesized, higher baseline severity, disability or co-morbidity as indexed by strength of dysfunctional agoraphobic cognitions; duration of current episode of PD; self-ratings of panic severity; and the 36-item Short Form Health Survey (SF-36) (Mental component) score were all found to predict poorer outcome with brief CBT. A similar trend was apparent in relation to baseline level of depression. With high and low end-state functioning as the outcome measure, however, only the treatment×agoraphobic cognitions interaction was found to be significant.

While there was no evidence that the above variables necessarily contraindicate the use of brief CBT, they were nevertheless associated with greater overall levels of post-treatment improvement with the 12-week approach.