Behau. Res. Ther. Vol. 31, No. 2, pp. 211-213, 1993 0005-7967/93 $6.00 + 0.00 Printed in Great Britain. All rights reserved Copyright 0 1993 Pergamon Press Ltd

Predicting outcome after treatment for generalised anxiety disorder

GILLIAN BUTLER

Department of Clinical Psychology, Warneford Hospital, Headington, Oxford OX3 7JX, U.K.

(Received 9 April 1992)

Summary-A previous paper, Butler and Anastasiades (Behaviour Research and Therapy 26, 531-534, 1988) presented evidence for three reliable predictors of response to Anxiety Management in patients with generalised anxiety disorder. It was argued there that these reflected severity of anxiety, demoralisation and depression. A second study (Butler, Fennell, Robson & Gelder, Journal of Consulting and Clinical Psychology, 59, 167-175, 1991) has compared two treatments for GAD: Behaviour Therapy and Cognitive Behaviour Therapy. Data from this study is used here to answer two questions: (i) do the same three variables predict outcome in the second study? The answer to this question is ‘no’; and (ii) which variables contribute to prediction of outcome when these two treatments are compared? Information presented here suggests that this depends partly on the nature of the treatment given. Outcome after behaviour therapy is predicted by initial levels of anxiety only, but the gains made are also relatively modest. Outcome after cognitive behaviour therapy is predicted by the degree to which ambiguous (external) information is interpreted as threatening. Thus a cognitive variable contributes reliably to the prediction of outcome after a cognitive treatment, but does not predict in the same way to outcome after a behavioural treatment.

INTRODUCTION

In 1988 we reported that we had been able to identify three reliable predictors of outcome after treatment with Anxiety Management for patients with a primary diagnosis of generalized anxiety disorder (GAD; Butler & Anastasiades, 1988). The same three variables contributed to prediction of outcome after treatment and 6 months later, and their pre-treatment values classified 80% of the patients correctly into good or poor responders. The findings suggested that lower initial levels of anxiety and of demoralisation together with a higher level of depression rated by an independent assessor, predicted a better outcome. Those patients who were more anxious to start with, and in addition more demoralised as reflected in a O-8 self-rating of ‘the degree to which their symptoms had got them down’, responded less well. However if they were also more depressed the outcome was better. This finding indicates that, for a given level of anxiety and demoralisation, the more depressed patients responded relatively well to treatment, possibly because depression was in this case a secondary consequence of GAD, and when the anxiety was successfully treated both problems resolved.

A second outcome study has recently been completed (Butler, Fennell, Robson & Gelder, 1991) in which two treatments for GAD were compared: Cognitive Behaviour Therapy (CBT) and Behaviour Therapy (BT). The results show that outcome after CBT was consistently better than outcome after BT whether measured immediately after treatment or 6 months later. The superiority of CBT was reflected in all three sets of measures used: those of anxiety, of depression and of cognition. In this brief report the data from this second study is analysed in order to find out whether the same three variables contribute to the prediction of outcome when patients with long-standing GAD are treated with either CBT or BT, rather than with Anxiety Management, which combines aspects of both the other treatments.

METHOD

Details of the clinical trial, in which the methods of data collection are described, are available from Butler et al. (1991). Only information necessary for understanding the analyses reported in this paper is provided here.

Outline of the study

Patients suffering from GAD (DSM-III-R) were randomly allocated to CBT, BT or to a Waiting List control group (WL). Patients in the WL group were also allocated randomly to either CBT or BT at the point of entry into the study, and started treatment three months later. Assessments were made before and after treatment or the waiting period, and 6 months after treatment had ended.

Fifty-seven patients entered the study, 19 in each of the three groups. Of these, 28 were originally allocated to CBT and 29 to BT, including those who did not start treatment until after the waiting period was over. Complete data is available for 52 patients post treatment (CBT = 27; BT = 25), and for 49 patients at 6 month follow-up (CBT = 27; BT = 22). All patients for whom complete data were available have been included in these analyses. Reasons for greater attrition in the BT group are discussed in Butler et al. (1991) and Butler and Booth (1991).

Statistical analyses

Stepwise multiple regression was used to identify significant predictors of outcome after treatment and also 6 months later. The analysis was carried out in two stages:

(i) Stage 1: the three variables that had contributed to prediction of outcome in the previous study were forced into the regression on the first three steps, so as to find out whether the same three variables contributed to prediction in the second study.

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(ii) Stage 2: this restriction was removed so as to find out which, if any, variables contributed to prediction of outcome in the second study.

Measures

Outcome variable. The Leeds Anxiety Scale was used as the measure of outcome as this was the measure used in the previous study.

Independent variables. A subset of the main measures of mood and of cognitions was selected from amongst the 6 measures of anxiety, 4 of depression and 6 of cognition, duration of GAD and neuroticism. These included both self-ratings and ratings by the assessor of anxiety: the Leeds Anxiety Scale (LAS) (Snaith, Bridge & Hamilton, 1976); Beck Anxiety Inventory (BAI; Beck, Brown, Epstein & Steer, 1988); O-8 ratings both by the patient and the assessor (Watson & Marks. 1969); trait-anxiety (STAI-trait; Spielberger, Gorsuch & Lushene, 1970); the Beck Depression Inventory, (BDI; Beck, Ward; Mendelson, Mock & Erbaugh, 1961), and the main measures of cognition. These were the Dysfunctional Attitude Scale (DAS; Rush, Weissenberger & Eaves, 1986); the Cognition Checklist (Beck, Brown, Eidelson, Steer & Riskind, 1987); Interpretations (Butler & Mathews, 1983) and Subjective Probabilities (Butler & Mathews, 1983).

RESULTS

Stage I. Do the same three variables contribute to prediction of outcome in the two studies?

Only one of the original three variables, anxiety measured by the LAS, made a significant contribution to the prediction of outcome in the second study. Initial levels of anxiety on this measure explained 16% of the variance in outcome post treatment (multiple regression coefficient = 0.40, P < 0.01) and 23% of the variance (multiple regression coefficient = 0.48, P < 0.01) 6 months later. There is no evidence here to suggest that the other two variables, reflecting demoralisation and depression, contributed to prediction in the same way as had previously been observed.

Interpretation of Stage 1. Two main differences between the studies will be considered at this point: (i) differences in acceptance criteria; and (ii) differences in the treatments given.

(i) Acceptance criteria for the first study specified that duration of GAD should be limited to between 6 months and 2 yr. The main reason for this decision was uncertainty at that time about how to apply criteria for diagnoses of co-existing personality disorders. In the second study no maximum limit was placed on the duration of GAD. One possibility therefore is that the longer GAD has persisted the longer aspects of demoralisation and depression, including relevant thinking styles, have had to become entrenched and the harder they are to change, regardless of the nature of the treatment given. Although variability in the measures reflecting demoralisation and depression remains, it may thus no longer be related to outcome in an orderly way.

However, it is also possible that the cognitive treatment provided in the second study would be able to deal well with such cognitions, and therefore predictive factors could differ according to the type of treatment received. If cognitions such as those associated with demoralisation and depression were adequately dealt with during treatment, then these factors would no longer contribute to prediction, but this time because outcome would be equally good irrespective of their initial levels. If they were not dealt with at all, as in BT, then the impact of the treatment might generally be limited (as indeed was observed), and outcome would not be related to initial scores on these measures either. Neither of these arguments applies in the case of Anxiety Management, the treatment used in the first study, which included a brief, and less sophisticated method for dealing with cognitions. This method might have been effective in relatively simple cases. but less so-in the more complex ones, f& whom more complex and systematic cognitive techniques would be required. This could account for the previously observed relationship between outcome and initial scores on these variables. Thus it is clearly important to address the question as to whether different factors contribute to the prediction of outcome in the two treatment groups compared in the second study. (More details of the content of all three treatments can be found in Butler & Booth, 1991).

Stage 2. Which variables contribute to prediction of outcome when two treatments for long-standing GAD are compared?

This question was answered using a ‘free’ stepwise multiple regression, without forcing in any variables. The analysis was applied first to the whole sample, and second to the CBT and BT groups separately.

The first finding is that only two variables contribute significantly to prediction in the whole sample. The first of these is anxiety as measured by the LAS: multiple regression coefficient = 0.40 post treatment and 0.51 6 months later, P i 0.01 in each case. The second is one of the measures of cognition, Interpretations: multiple regression coefficient = 0.46 post treatment and 0.57 6 months later (contributing an additional 5 or 6% of the variance) P < 0.06 post treatment and P < 0.05 6 months later. The prediction could not be significantly improved by the addition of any other variables. It may be worth noting however that, as in the first study, depression (measured by the BDI) appeared to relate negatively to outcome: i.e. there was a non-significant tendency in this study, and a significant one in the first study, for the more depressed patients, for a given level of anxiety, to have lower anxiety scores after treatment.

The second finding is that different variables were found to contribute to prediction of outcome in the two groups of patients. For those treated with CBT, only Interpretations contributed significantly to prediction: multiple regression coefficient = 0.55 post treatment and 0.65 6 months later, P < 0.01 in each case. Scores on this measure alone explained 42% of the variance in outcome 6 months after treatment had ended. For those treated with BT, only the LAS contributed significantly to prediction: multiple regression coefficient = 0.51 post treatment and 0.56 6 months later, P < 0.01 in each case.

The Interpretation questionnaire. This measure was developed by Butler and Mathews (1983). Brief, ambiguous, scenarios are presented, for example: “Not long after starting a new job your boss asks to see you”. Three possible explanations are provided, only one of which reflects an interpretation in terms of threat (e.g. “you have not been doing the job properly”). The rank order of these interpretations made by the patients reflects the degree to which they interpret ambiguous information as threatening. The version used in this study has three subscales, reflecting different sources of anxiety: (i) external threat (e.g. “When you get home you find a message to contact a relative”: threatening interpretation, “someone has died”); (ii) internal threat (e.g. “Your heart is beating quickly and pounding”, threatening interpretation: “There is something wrong with your heart”); and (iii) social threat (e.g. “You are at a party and notice that some people are looking in your direction”, threatening interpretation: “They are criticising you”). Although patients with GAD might have all three types of worries, they might be most easily distinguished by their sensitivity to external threats. It is for

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instance likely that internal threats would be more alarming to patients with panic disorder and social threats would be more alarming to patients with social phobia.

It was therefore possible to find out whether the three subscales predicted equally well in GAD patients. The multiple regression showed that the external subscale carried the whole weight of the prediction in this sample. For the CBT group only, the external subscale of the Interpretations questionnaire contributed 41% of the variance in outcome post treatment and 44% of the variance in outcome 6 months later. The multiple regression coefficient post treatment was 0.64 (P < 0.01) post treatment, and 0.66 (P i 0.01) 6 months later. Neither of the other subscales, nor any of the other variables made any further significant contributions to predictions of outcome for patients treated with CBT.

DISCUSSION

Summary of findings

An analysis of predictive factors after treatment for GAD is presented. This analysis was based on a previous study in which it was found that three variables consistently contributed to the prediction of outcome after treatment with Anxiety Management. In the first stage of the analysis these three variables were forced into the stepwise multiple regression in order to find out whether they would also predict outcome in the new study. The previous results were not replicated, and interesting new findings are described.

These suggest that different factors contribute to the prediction of outcome in groups of patients treated in different ways. For those treated with BT only anxiety predicts outcome. The more anxious these patients are before treatment the more anxious they are likely to be subsequently (despite making relatively small but nevertheless significant improvements). The most likely finding in all such studies is of-course that there will be a strong relationship between the outcome variable and earlier scores on this same variable. However it is interesting that no other variables contributed to prediction as well, and in particular that there appears to be no systematic relationship between thoughts at the beginning of treatment and level of anxiety at the end of treatment for patients treated with behaviour therapy.

For those patients who receive a cognitive treatment (CBT) a cognitive variable contributes significantly to prediction of outcome. This cognitive variable reflects the degree to which patients interpret ambiguous, external, situations as threatening. The more likely they are to interpret such things as threatening before treatment, the higher their anxiety is likely to be afterwards, despite having received a demonstrably effective cognitive treatment.

Interpretation and comment

The sample of patients studied here is small, and the main value of these results is therefore to raise questions for further study.

The single most important predictor of outcome after treatment with CBT appears to reflect ‘apprehensive expectation’ or worry, the main, cognitive defining feature of GAD. At the same time the aspect of this predictor that relates most strongly to outcome also reflects a concern about external, general, threats as opposed to types of threats more commonly described by patients with panic disorder or social phobia. This finding suggests that, if treatment is to be effective irrespective of the initial level of anxiety, it is important to deal effectively with the tendency to interpret ambiguous, external, information as threatening. However when this tendency is long-standing it may be evident in assumptions and schemas which are relatively hard to change during brief treatment (up to 12 sessions in this case). Thus the more entrenched this way of thinking is, the higher will be the Interpretations score before treatment and the higher will be the anxiety score afterwards.

The interpretations questionnaire has also been found to contribute to the prediction of outcome in the treatment of panic disorder (Clark, Salkovskis, Hackmann, Anastasiades & Gelder, 1992). Together these findings lend support to the idea that misinterpretations of various kinds, not only of bodily symptoms as in panic disorder, but also of a range of external events and situations, play an important part in the maintenance of anxiety.

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Beck, A. T., Ward, C. H., Mendelson, M., Mock, J. & Erbaugh, J. (1961). An inventory for measuring depression. Archives of General Psychiatry, 4, 561-511.

Beck, A. T., Brown, G., Eidelson, J. I., Steer, R. A. & Riskind, J. H. (1987). Differentiating anxiety and depression: a test of the cognitive content-specificity hypothesis. Journal of Abnormal Psychology, 96, 179-183.

Beck, A. T., Brown, G., Epstein, N. & Steer, R. A. (1988). An inventory for measuring clinical anxiety: psychometric properties. Journal of Consulting and Clinical Psychology, 56, 893-897.

Butler, G. & Anastasiades, P. (1988). Predicting response to anxiety management in patients with generalised anxiety disorder. Behaviour Research and Therapy, 26, 531-534.

Butler, G. and Booth, R. (1991). Developing psychological treatments for generalized anxiety disorder. In Rapee, R. M. and Barlow, D. H. (Eds), Chronic anxiety and generalized anxiety disorder. NY: Guilford Press.

Butler, G. & Mathews, A. (1983). Cognitive processes in anxiety. Advances in Behauiour Research and Therapy, I, 5162. Butler, G., Fennell, M., Robson, P. and Gelder, M. (1991). Comparison of behavior therapy and cognitive behavior therapy

in the treatment of generalized anxiety disorder. Journal of Consulting and Clinical Psychology, 59, 167-175. Clark, D. M., Salkovskis, P. M., Hackmann, A., Middleton, H., Anastasiades, P. and Gelder, M. (1992). A comparison

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Snaith, R. P., Bridge, C. W. K. & Hamilton, M. (1976). The Leeds scales for the self-assessment of anxiety and depression. British Journal of Psychiatry, 128, 156-165.

Spielberger, C. D., Gorsuch, R. L. & Lushene, R. E. (1970). Manual of the state-trait anxiety inventory. Palo Alto: Consulting Psychologists Press.

Watson, J. P. & Marks, I. M. (1971). Relevant and irrelevant fear in flooding-a crossover study of phobic patients. Behauior Therapy, 2, 215-293.