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PREDICTION OF OUTCOME WITH GROUP COGNITIVE THERAPY FOR DEPRESSION

DAVID J. KAVANAGH* and PETER H. WILSON Badham Chnic. Department of Psychology, University of Sydney, N.S.W. 20% Austraha

Summary-This paper tested a social-cognitive model of depressive episodes and their treatment within a predictive study of treatment response. Clinically depressed ~ohmteers were given self-efficacy questionnaires and other measures before and after they were treated with cognitive therapy, and their progress was monitored over the succeeding 12 months. Improvements in depression during treatment were closely associated with self-efficacy regarding control of mood and with self-monitored levels of negative cognition. Remission over the following 12 months was predicted by the initial response to treatment, by a shorter duration of the episode prior to treatment, and by a post-treatment assessment of self-efficacy regarding control of negative cognition. Self-efficacy remained a significant predictor after post-treatment depression scores and episode duration were entered in a prediction equation. However, a programme of additional treatment based on the depression model did not result in improved depression status. Apart from the failure of the additional treatment. the results are consistent with a social-cognitive model of depressive episodes that emphasises the role of self-efficacy and skills regarding control of negative moods.

During the last 15 yr there has been a steady growth in the literature on psychological treatment for depression. One major psychological approach has been cognitive therapy, which has been advanced by Beck and his colleagues (Beck, Rush, Shaw and Emery, 1979). This approach assists clients to identify depressogenic cognitions and irrational beliefs and to subject these cognitions and beliefs to logical analysis and empirical testing. There is now substantial evidence that these and other simiiar cognitive-behaviourai strategies are very effective treatments for depression in the short term (Becker and Heimberg, 1985; Blaney, 1981). In fact some studies have found that cognitive therapy is at least if not more effective than antidepressant medication (Rush, Beck Kovacs and Hoffon, 1977; Simons, Murphy, Levine and Wetzel, 1986).

A continuing problem for all treatments of depression is the mai~tenan~ of improvem~ts after the treatment is concluded (Baker and Wilson, 1985; Kovacs, Rush, Beck and Holion, 1981; Teasdale, FennelI, Hibbert and Amies, 1984). At this stage little is known about the factors that predispose clients to relapse. Gonzales, Lewinsohn and Clarke (1985) found a set of predictors that were similar to those in the existing psychiatric literature (e.g. higher number of previous episodes, family history of depression), but these relationships were weak and failed to account for a substantial amount of variance. In some other problem domains, the concept of self-efficacy has proved to be useful (Bandura, 1977, 1982). Self-e!Ticacy judgments are highly predictive of performance and are advanced by Bandura (1977) as a central mechanism of change during treatment. Studies on smoking cessation programmes have also shown that self-efficacy measures can contribute strongly towards predicting relapse (Condiotte and Lichtenstein~ 198 I; DiClemente, 1981). Setf-efficacy may provide a similar function in the prediction of depression foffowing treatment.

Kavanagh (1983; cf. Bandura, 1982; Teasdale, 1985) advanced a model of depression that highlights the role of self-efficacy and skills in the development and termination of depressive moods. One aspect of the model is that people are more likely to avert or abort a depressive episode if they are confident regarding their performance on mood-relevant tasks and possess the skills that are required to produce a positive outcome (Bandura, 1977, 1982). Any tasks that are associated

*To whom ah correspondence should be addressed.

334 DAVID J. KAVANAGH and PETER H. WILSON

with highly attractive or aversive consequences for an individual are considered to be mood- relevant, but the task domain that is probably most relevant to a depressive episode is the person’s control of transitory dysphoria so that its duration and intensity are minimised. In addition to skills that may be required to terminate the aversive situation, control of dysphoria is likely to involve strategies such as challenging negative cognitions and increasing pleasurable activity (Beck et al., 1979; Brown and Lewinsohn, 1984). Cognitive-behavioural treatment for depression focuses on these skills for mood control.

Within this view of depression, improvements in mood during treatment are expected to parallel increases in mood control skills, whereas improvement in untreated Ss should result from serendipitous changes in the person’s situation. The model also predicts that the course of depression during a follow-up period will be related to skill attainments in these critical skills. Self-efficacy about control of depressive moods is expected to add to our ability to predict relapse by allowing Ss to predict new situational challenges as well as directly affecting mood by reducing anxiety about recurrences and by leading to the investment of greater effort and persistence in the application of the strategies (Bandura, 1982).

Consistent with the model, a preliminary study by Yusaf and Kavanagh (1989) found that changes in depression scores during a broad spectrum cognitive-behavioural treatment were associated with improvements in self-efficacy and performance attainments regarding pleasant activity, social competence and control of negative cognition. In contrast, changes in depression within a Waiting List control group were not associated with changes in perceived control over moods. Depression scores at the end of a 3-month follow-up period were significantly predicted by post-treatment measure of self-efficacy and reported skill attainments. A partial replication of this work is required with a larger sample, a longer follow-up period and with other interventions such as a specifically cognitive treatment.

Concerns about the progress of clients during follow-up should not be restricted to prediction, but ideally should extend to the provision of more effective treatments. One strategy in attempting to improve long-term effectiveness is to provide some form of booster or additional treatment. So far, this strategy has not proved successful (e.g. Baker and Wilson, 1985). However, in Baker and Wilson (1985) the additional treatment was delivered in a standard format for all Ss. Perhaps the additional treatment would have a greater impact on relapse if it were individualized, focusing on each person’s expected vulnerabilities from assessments that are based on the depression model.

The present study aimed to examine the social-cognitive model of depression within a treatment programme. We attempted to examine correlates of improvement during cognitive treatment for depression and predict outcomes during a 12-month follow-up from post-treatment assessments of critical variables. A secondary goal was to pilot a brief programme of additional treatment. Clinically depressed volunteers were given self-efficacy questionnaires and other measures before and after they were treated with cognitive therapy in groups. Then Ss were followed up over the next 12 months. Three months after the group treatment we offered individually-tailored sessions to a random half of the treatment responders. These additional sessions focused on managing perceived stress, maximising social resources and reducing the incidence of aversive events, as well as revising material that was taught in the original treatment sessions.

METHOD

Subjects Ss were recruited by newspaper and radio publicity that invited depressed people who wished

to volunteer for a treatment study to telephone the University of Sydney. Callers who were aged between 20 and 65 yr and who lived or worked within travelling distance of the University (n = 292) were mailed a biographical questionnaire and a Beck Depression Inventory (BDI; Beck, Ward, Mendelson, Mock and Erbaugh, 1961). Ninety-five respondents who scored at least 18 on this BDI, were not in any concurrent psychological, psychiatric or psychopharmacological treatment and who did not show evidence of other major psychiatric conditions attended an interview to assess their depression status. At the interview, 57 individuals who again fulfilled these conditions and also met the criteria for Major Depressive Episode in DSM-III (American Psychiatric Association, 1980) were accepted for the study. The 42 Ss who completed treatment consisted of 19 male and

Prediction of treatment outcome in depression 335

23 females, whose age ranged from 22 to 60 yr (M = 40.1). These Ss had a mean of 12 yr of forma1 schooling (ranging from 9 to 19 yr). Twenty-five (57%) were living with a spouse or defaeto spouse at pre-test.

Measures

Depression. The BDI was selected as the primary measure of self-reported depression severity because of its wide usage and demonstrated reliability and validity (Beck, Steer and Garbin, 1988). An independent measure of depression was obtained using the Hamilton Rating Scale for Depression (HRSD; Hamilton, 1960). Ham&on interviews were audiotaped and one of two raters (blind as to whether the interview was pre- or post-treatment) subsequently completed the scale. Inter-rater pliability was assessed on a random subset of 16 interviews, resulting in a correlation of 090. During the rating procedure we belatedly discovered that one of our tape recorders had been malfunctioning and although estimated ratings were available from the interviewers, these ratings were not blind as to measurement occasion. We have accordingly reported only the data from the 31 Ss whose audiotapes were deciferable both before and after treatment.

Cognition Efficacy Questionnaire (CEQ). The first of the self-efficacy scales, the CEQ, asked three questions relating to the Ss’ expected actions each day over the next 12 months: (1) “How much time can you make at least moderately enjoyable?” (2) “How much time can you have without any sad, discouraging or unpleasant thoughts?’ and (3) “What percentage of the negative thoughts that pop into your mind can you effectively challenge ?’ In each case, 10 levels of performance were outlined, from 30 min or more to 12 hr or more. or from 10 to 100% for question (3). A single column rating method was used, from 0 “can’t do it”, to SO, “‘moderately certain can do it”‘, to 100, “certain can do it”. This format preserved the intention of measuring self-efficacy on a probability scale (Bandura, 1977, t 932). while ensuring that confidence ratings would be available for all performance levels rather than just the one that Ss indicated they could achieve (cf. Bandura, 1984; Eastman and Marzillier, 1984; Kavanagh and Hausfeld, 1986). The estimate of self-efficacy strength from this set of questions was the average confidence rating across all items, and represented a rating that was generalized across the three tasks and over time. We administered the CEQ to 110 unselected students from Psychology I (88 women and 22 men). This confirmed that the CEQ had high internal consistency over its three questions, ti = 0.80. As expected, students who saw themselves as more depressed on the BDI had lower self-efficacy on the scale, r = -0.51, P < 0.001. Twelve to i 5 months after the first assessment, we retested 68 of the students who could be contacted, The test-retest reliability of the CEQ was 0.61, P < 0.001.

S@ess Conrrol ~~e~i~~#~~~re @C@ Th e second self-efficacy scale, the SCQ_ was designed to measure Ss’ predictions regarding the occurrence of potentially stressful life events and their belief in their ability to cope with these events. Thirty events or situations were generated from the literature on depression and life stressors (e.g. Billings and Moos, 1985; Henderson, Byrne and Duncan-Jones, 1981; Lewinsohn and Talkington, 1979; Paykel, 1979). These included both major life events such as the death of an immediate family member or close friend and ongoing stresses such as frequent arguments at home or frequently having too much to do. We asked two questions about each event: (1) how likely is it that this event will occur over the next 12 months, from O%, “certainly will not occur”, to lOO%, “certainly will occur” and (2) how confident are you that you can prevent yourself having a episode af depression if the event does occur, from 0%: “Can’t prevent a depressive episode;” to 100%: “Definitely can prevent a depressive episode”. From these answers we derived a stress control score, consisting of the number of events: (a) that were judged to be less than moderately likely ( < 50%) or (b) where the person was at least moderately certain that he/she could prevent a depressive episode if the event occurred (confidence 3 50 on the self-efficacy scale). The correlation of the SCQ with the BDI was -0.50, f < 0.001 among the sample of unselected undergraduates. Over the 12-15 month retest interval, the SCQ had a reliability coefficient of 0.59, P < 0.001.

Interpersonal Concerns Questionnaire (ZCQ). Because of interest in the literature concerning the role of social skills in depression (e.g. Coyne, 1976; Jacobsen and Anderson, 1982; Youngren and Lewinsohn, 1980; Zeiss, Lewinsohn and Munoz, 1979), we also included a third efficacy scale, the self-efficacy section of the ICQ (Kanfer and Zeiss, 1983). The ICQ asked whether Ss could perform 24 social activities such as asserting themselves, accepting an invitation or sharing affection, with


people encountered in home, social and work settings. For each item that Ss thought they could perform, they judged how well they thought they could perform it on a IO-point scale (where poor performances received a rating of 1). These scores were used by Kanfer and Zeiss as indicators of self-efficacy strength. Consistent with Bandura’s method of calculating self-efficacy strength, we obtained an average strength score by dividing the total strength ratings by the number of items. Since social skills were not specifically targetted in treatment, changes in self-efficacy on the ICQ would represent generalized improvements rather than specific treatment reactions. As a result we did not expect that ICQ scores would be strongly related to depression improvement or would be a strong predictor of long-term outcomes (cf. Yusaf and Kavanagh, 1989, where such skills were specifically trained in the course of treatment).

Self-Monitored Cognition (SMC). The SMC comprised a set of daily self-monitoring measures that corresponded with the questions in the CEQ. Mean ratings over 7 days were standardized for each question, and the monitoring score represented the average standard score across the three questions.

Self-Control Schedule (SCS). The SCS of Rosenbaum (1980) is a 36-item questionnaire that aims to measure: (a) use of cognitions to control unpleasant emotional and physical reactions, (b) application of problem-solving strategies, (c) ability to delay gratification, and (d) self-efficacy about self-control. A recent study by Simons, Lustman, Wetzel and Murphy (1985) had found that Ss with high initial SCS scores had a better response to cognitive therapy than those with low scores, and low scorers responded better to pharmacotherapy. While the main focus of our study was on the process of change and the prediction of follow-up status, we took the opportunity to replicate the Simons et al. (1985) prediction of responses to cognitive therapy from the SCS.

Other measures included age, gender, number of years of formal education, and the estimated duration of their depression. Depression duration was coded in five categories: (1) < 3 months, (2) 3-6 months, (3) 7-12 months, (4) l-2 yr, and (5) > 5 yr. Ss also recorded the number of events from the SCQ list that had occurred over the last 12 months prior to the pre-test, or since the last assessment in the case of post-treatment and follow-up measures.

Procedure

Initial assessment. Ss completed the CEQ, SCQ and SCS at the end of the selection interview, and the first SMC measure was obtained during the second week of therapy. Respondents who did not meet the criteria were offered treatment at the University Psychology Clinic or were referred elsewhere.

Treatment. The treatment intervention was conducted in groups of four to nine people and consisted of nine 2-hr sessions the first four of which were weekly and the remaining five at fortnightly intervals. It consisted of cognitive therapy after Beck et al. (1979) and was described in the treatment manual of Wilson and Kavanagh (1985). Treatment encouraged clients to: (1) identify negative cognitive distortions and irrational beliefs, (2) self-record events, cognitions and mood, (3) examine the validity of automatic negative thoughts, (4) develop and use positive counterstatements, (5) undertake assignments designed to increase the frequency and quality of positive activities, and (6) challenge irrational beliefs and assumptions using rational dialogue and data from assignments. The two therapists had recently completed their clinical training which had included substantial experience in treatment of depression. Each had also completed a previous treatment study on depression (Baker and Wilson, 1985; Yusaf and Kavanagh, 1989). They met with the second author at 1-2 weekly intervals for consultation sessions.

Assessment of treatment outcome. Post-treatment assessment was conducted at the ninth session. Ss were followed up over the succeeding 12 months after treatment. In the middle of each 3-month period Ss were mailed a BDI which they completed and returned by post. At 3, 6 and 12 months they were telephoned and asked to attend an interview at which the BDI was administered and their depression status since their last assessment was reviewed using DSM-III criteria. Ss also indicated whether or not any of the events on the SCQ had occurred over the period. To conserve research funds, assessment at 9 months was restricted to a mailed BDI and questionnaires about events and any further treatment.

Additional treatment. Three months after the initial treatment, half of the Ss who had shown a positive initial treatment response were offered additional treatment. Allocation was random,


with control for post-treatment BDI scores. The additional treatment was provided in 5-7 individual weekly sessions over a median of 11 hr (range 7-13 hr). Its content was derived from the depression model, in that it focused on further increasing skills regarding mood control and in reducing both the incidence and impact of aversive events. The objectives were to review the material in the original treatment, and to provide additional individually-tailored interventions as required to: (a) decree the number and intensity of the person’s expected critical events, (b) reduce their negative reactions to stress, and (c) increase the range and frequency of their positive social interactions (especially with their spouse or partner). Treatment elements comprised training in relaxation, problem solving skills, increasing positive communications, assertion, and brief behavioural marital therapy. SCQ data and a behavioural assessment were used to select elements for particular emphasis. Details of treatment are provided in the manual by Kavanagh and Wilson (1986). Nine Ss completed this treatment, and 10 were in the control group. Five Ss who declined to attend further sessions were excluded from the evaluation of the additional treatment.

RESULTS

Sample attrition

Four Ss withdrew from the study before attending any sessions, reducing the study sample to 53. Of these, 11 more (21%) dropped out during treatment, including three Ss who entered individual treatment, one who left the country and three who could not attend because of employment schedules or illness. There were no follow-up data for two or more 3-month periods for four Ss (three of whom did not initially respond to treatment). One of these Ss was known to have sought inpatient treatment during follow-up, and another was judged depressed on DSM-III criteria at the 3-month interview. The remaining Ss were clearly nondepressed at their two available follow-up assessments, and had mean BDI scores across assessments of 8.5 and 5.5 respectively. Rather than risk incorrect inferences about missing data, all four Ss were withdrawn from the follow-up analyses. Data for one of the four follow-up assessments were unavailable for eight more Ss (three responders and four nonresponders), and their average results for the three remaining periods were substituted.

Response to treatment

A positive initial response to treatment was defined as a BDI score of less than 18 at post-treatment (the criterion for entry into the study) and a decrease of at least one standard deviation (8.5 points) during treatment. Using these criteria, 26 Ss (or 62% of those who completed treatment) were classed as responders. These Ss had a median BDI decrease of 15.5 points (Range 9-39) and a median post-treatment BDI of 9.5 (Range 9-16). Thirteen Ss (31%) would have met a more stringent outcome criterion of a post-treatment BDI < 9.

Table 1 summarizes the pre/post results for Ss who completed treatment. Univariate tests showed pre/post improvements on all variables including the HRSD, which fell from a mean of 17.10 at pre-test to 7.16 at post-treatment, F( 1,30) = 48.37, P < 0.001. Scores on the CEQ and SCQ approached the means obtained on the undergraduate sample, which were M = 60.57, SD = 17.82 and M = 26.74, SD = 4.15 respectively. The absence of a control group of course precludes a confident ascription of these effects to treatment.

Prediction of initial treatment response

A social-cognitive model of depression does not entail any ability to predict a treatment response from pre-treatment variables, since the treatment method should compensate for initial subject differences. However, because of interest in this subject within the literature (e.g. Simons ef al., 1985) we undertook a stepwise discriminant function analysis to predict initial responses to treatment. The predictor variables were gender, age, education, episode duration, and pre-test assessments of stressful event occurrences, BDI, CEQ, SCQ, ICQ, SMC and SCS. Contrary to Simons et al. (1985) the SCS did not signifiantly predict treatment response. The only variable that individually discriminated the groups with a univariate P < 0.05 was the number of stressful events that had occurred over the last 12 months, ~(1,40) = 5.53, P c 0.03. Ss who had more of these events (M = 10.52 events) responded better to treatment than those who had experienced fewer


Table I. Response to treatment

Pre POSI M M Pre-Post Uncorrected

Measure

Beck (BDI)

n (SD) (SD) F P 42 27.48 14.71 74.02 0.001

Hamilton (HRSD)

(6.61) (8.67)

31 17.10 7.16 48.37 0.001 (5.74) (5.59)

Cognition Efficacy (CEQ) 41 36.51 56.34 26.68 0.001 (20.24) (20.23)

Self-Monitored Cognition (SMC) 35 0 0.43 6.50 0.025 (0.84) (1.05)

Stress Control (SCQ) 42 20.24 24.40 17.21 0.01 (6.65) (5.76)

Interpersonal Concerns (ICQ) 40 4.29 4.98 8.58 0.01 (1.74) (1.86)

Self-Control (SCS) 42 - 13.10 6.17 27.75 0.01 (22.69) (25.92)

stressors (M = 7.25 events). This variable alone correctly classified 71.4% of cases, and no other variable significantly improved the discriminant function. The effect was not simply due to an association between stressors and higher BDI scores at pretest, so that high scorers would appear to respond more strongly because of regression to the mean. Pre-test BDI scores did not discriminate treatment responders from non-responders, F( 1,35) = 0.07, NS, and the correlation between BDI and event occurrences was 0.10, NS. Nor could the effect be due to any other variable such as episode duration, since no other predictors were significant.

Correlates of initial improcement in depression

Because of the emphases in our treatment, we expected that three variables would be closely associated with a drop in BDI depression scores from pre- to post-treatment. These variables were gains over the course or treatment in self-efficacy on the CEQ and SCQ, and improved control of negative cognition on the SMC. We forced entry of these three variables into a multiple regression equation and found that they produced a multiple R of 0.81, with increases on the CEQ alone correlating 0.71, P < 0.001 with falls in BDI scores. Each of the variables contributed significantly to the equation, which was -6.380 + 0.005 CEQ + 2.687 SMC + 0.547SCQ. Gender, age, education episode duration, number of stressful events in the last 12 months, and improvements on the ICQ and SCS were then added to the equation, but their inclusion did not significantly improve prediction (P > 0.20). A stepwise multiple regression derived the same equation as the forced entry.

Depression status during follow -up

Ss were considered to be remitted during a 3-month period of follow-up only if they: (a) scored < 18 on the BDI measures, (b) were not prescribed a treatment dosage of antidepressant medication (defined as more than 50 mg daily), (c) did not obtain any further treatment for depression (apart from our controlled trial of additional treatment), and (d) were not judged to have met DSM-III criteria for Major Depressive Episode at any time since their last interview assessment. Only 26.3% of the 38 Ss in the follow-up sample were remitted throughout the whole 12 months follow-up. Twenty-three of the 28 nonremitted Ss violated more than one criterion for remission, and only 3 were judged nonremitted solely on their BDI scores. The high degree of nonremission is reflected in the number of Ss in the full sample who received medication or other treatment over the 12 months: Excluding the additional treatment trial this number amounted to 18, or 47.4%. The number rose to 24, or 63.2% if treatments for anxiety or other psychological problems were included.

Presence of a confirmed depressive episode required both that Ss satisfied DSM-III Major Depressive Disorder criteria and also scored 18 or more on the BDI. Forty-two percent of the sample experienced a new episode or a continuation of their original episode during one or more of the 3-month follow-up periods.


These data on follow-up status include 14 Ss who did not show an initial response to treatment, so that they represent both continuations of the presenting episode and the occurrence of exacerbations. When we select the subset of 24 Ss who were initially improved on our criteria, 33.3% had a confirmed relapse, 29.2% had some data suggesting depression and 31.5% were remitted on all criteria throughout follow-up. The median remission time for improved Ss was 9 months. Results of 11 Ss who had a post-treatment BDI of 9 or less were similar. Four (36.4%) had a confirmed relapse, and 5 (45.5%) were confirmed as remitted, and the median remission time was over 9 months.

All of these figures on nonremission and relapse may be siightly underestimated becasue of our decision to include Ss who did not have data for one of the four follow-up assessments. Three of these Ss were judged to be fully remitted on the basis of their remaining follow-up assessment. This represents a maximum underestimation of 7.9% relapse in the full sample or 12.5% in the group of initially improved Ss.

Eflects of additional treatment

An analysis was undertaken of the maximum BDI scores over the 3 months before the additional treatment, the score immediately after the treatment, and maximum scores during each remaining 3-month period. This revealed that the additional treatment did not have a differential impact on self-reported depression. The interaction of treatment group and a time contrast comparing the 3-month assessment (i.e. pre-booster) with later assessments gave F( 1,17) = 0. t 3, NS. Because of these results the two groups of Ss were amalgamated in further analysis.

Prediction of follow-up status from post -treatment assessments

Intial treatment response andfollow-up. To predict the status of Ss during the follow-up period, first of all we compared the results of Ss who initially responded to treatment with Ss who did not respond. Maximum BDI scores for each period are shown in Fig. 1. From an equivalent BDI at pretest, F( 1,35) = 0.07, NS, improved and unimproved Ss displayed different courses over time. A comparison of the two groups across time from post-test through all of the follow-up measures showed that the improved group had significantly lower BDI scores, F(l,35) = 17.73, P c 0.001. A convergence of the group scores over the follow-up period was reflected in a significant interaction of group and time over the 12 months, F(4,140) = 2.63, P < 0.05. Despite this tendency initially improved Ss remained less depressed than their unimproved counterparts at the final assessment, F( 1,35) = 4.66, P c 0.05.

Self-eficacy and other measures as predictors of follow-up status. As discussed in the Intro- duction, we expected that post-treatment measures of depression and relevant self-efficacy scores might prove to be particularly important for prediction of follow-up status. Accordingly we attempted to predict the number of 3-month period that Ss were in remission, using a stepwise multiple regression and choosing post-treatment BDI, CEQ and SCQ as predictor variables. Both the CEQ (r = 0.59) and the SCQ (r = 0.48) had significant correlations with remission time. After entry of post-treatment BDI (r = -0.62), only the CEQ remained a significant predictor (FChange = 5.47, P < 0.03). The resultant equation was -2.214 - 0,080 BDI + 0.001 CEQ, which gave a multiple R of 0.68, P < 0.001.

We decided to test the adequacy of this model by applying a stepwise multiple regression that used seven additional predictor variables (gender, age, education, episode duration, ICQ, SMC and SCS). Despite the opportunity to capitalize on chance associations (particularly with the small sample size of 38), the only change was that episode duration (r = -0.40) entered on Step 2 (R = 0.72, F Change = 10.07, P c 0.005). Ss who reported a longer episode duration were more likely to be unremitted during follow-up. The CEQ entered on Step 3, producing a multiple R of 0.78, F Change = 6.70, P c 0.02. The prediction equation was 0.443 - 0.077 BDI - 0.583 Duration + 0.001 CEQ.

Depression and concurrent events

The Pearson correlation of the SCQ with remission status was comparable to the prediction of BDI scores by the preliminary sample of undergraduate students (r = -0.43), but in both analysis the SCQ effect disappeared after the entry of the first BDI. Similar results were obtained when


Responders In 123) - -** -

Nonr~sponders f n *i41 -*-

I I I I I Pro Post 3mo 6mo Smo Pm0

Asseument period

Fig. I. Follow-up BDI scores and initial response to treatment.

Table 2. Remission during follow-up and number of stressful events summed over

No. periods remitted* n No. events

4 periods 9 20.5 3 periods 9 35.9 2 periods 4 23.5 1 period 6 32.0 0 periods 9 43.5

*These are the number of 3-month assessment periods that Ss were remitted over the 12-month follow-up. Thus, a S who WBS remitted for 3 periods was remitted for 01 least 9 months, although not necessarily for 9 consecutive months.

average event likelihood and average self-efficacy scores on the SCQ were separately examined. This did not mean that the actual occurrence of events mentioned in the SCQ was unrelated to remission during follow-up. When the number of recorded events was summed over follow-up assessments (i.e. allowing for the same item to recur over multiple periods), Ss who reported more events were remitted over fewer follow-up periods, F(l,32) = 7.03, P < 0.01 (Table 2). Despite an apparent discrepancy from the linear trend for Ss who had 3 remitted periods the departure from linearity was not significant, F(3,32) = 1.99, P > 0.05. A second analysis counted the repeated events once only. When we compared Ss who were remitted during the entire year (n = 9) with those who were not (n = 28), remitted Ss had fewer stressful events during follow-up, A4 = 11.56, than did those who were not fully remitted, M = 15.93, F( 1,35) = 4.82, P c 0.04.

DISCUSSION

Together, the results are consistent with the model of depressive episodes advanced by Kavanagh (1983). In particular they support the idea that self-efficacy and skills regarding control of negative cognition mediates a sustained response to cognitive treatment for depression. Not only did mood control variables correlate highly with concurrent changes in depression scores during treatment, but a post-treatment measure of self-efficacy regarding control of negative cognition discriminated Ss who relapsed over the next 12 months. These results are highly consistent with the discriminant function analysis reported by Simons et al. (1986), who found that a post-treatment administration of the Dysfunctional Attitudes Scale (Weissman and Beck, 1979) entered an equation predicting relapse status of responders over the succeeding 12 months. The predictive contribution of our self-efficacy scale is also consistent with the contribution self-efficacy makes to prediction of relapse in some other problem domains (e.g. Condiotte and Lichtenstein, 1981; DiClimente, 1981) and supports a social-cognitive perspective of treatment outcome (Bandura, 1977, 1982).

Some readers may suggest that the result of these studies simply reflect one aspect of a depressive syndrome rather than separable process variables: that, for example, the predictive results are just indicating that the Ss who are least depressed at the end of treatment are least depressed at follow-up. This view is not supported by our observation that the cognitive control variables significantly contributed to prediction even after self-reported depression was entered into the equation (see also Simons et al., 1986). Apparently we can separate the cognitive control aspects of depression from the full syndrome, and these cognitions play a significant role in the process of improvement within cognitive therapy.

A puzzling feature of our results was the failure of the Stress Control Questionnaire to predict depression status during follow-up after post-treatment depression scores were partialled out. While a measure based on the most discriminating items of the SCQ may have promise, at this stage it seems to add little predictive power to a measure of current depression (cf. Baker and Wilson, 1985; Faravelli, Ambonetti, Pallanti and Pazzagli, 1986). The relatively poor showing for the SCQ occurred despite a strong relationship between actual stressful event occurrences and


relapse. While some of these events may have been consequences of depression rather than its

antecedents, the relationship between depression and stressful events suggests that the weak predictive power of the SCQ is primarily due to difficulties in predicting events and hypothetical coping reactions that may occur months into the future. In terms of the depression model, one alternative reading of these results is that the model should focus on self-efficacy and attainments regarding specific coping skills rather than on unspecified coping reactions to challenging events.

The failure of additional treatment to improve outcome is consistent with the findings of Baker and Wilson (1985) in which a cognitive-behavioural booster programme administered in groups did not improve the status of depressed Ss following initial therapy. We had thought that one possible reason for the failure of that programme was the lack of individual tailoring of treatment components, its delivery in a group format, and its administration to mixed groups of initial treatment responders and non-responders. The results of the present study cast doubt upon the validity of these explanations, since the programme was restricted to initial treatment responders and was both individually designed and delivered. Nor was the result due to a floor effect, since there was room for further improvement in depression scores. Comments by some Ss suggest that the treatment may have raised issues that could not be fully addressed without a much greater number of sessions than it was possible to deliver in this study. The rejection by some Ss of the offer to attend additional treatment may also have resulted in an undetected sampling bias in the treated group. Further research into additional treatment or other preventative approaches should control for these factors.

There are some aspects of the present study that should induce caution in interpreting the results. Given the relatively small number of Ss, the multiple regressions and discriminant functions clearly require replication. Secondly, the use of volunteer Ss introduces a potential problem in applying the results to other types of depression samples, although past research has suggested that clinic Ss and volunteers represent similar populations as long as stringent screening procedures such as the one in this study are employed (Hersen, Bellack and Himmelhoch, 1981). A further concern with breadth of application is raised by the relatively high level of post-treatment depression scores, compared with some other studies that have used cognitive therapy (e.g. Rush et al., 1977). The remission rate during the follow-up period of our study (26.3% for the full sample and 37.5% for treatment responders) was also somewhat lower than the rates found in some other cognitive therapy studies (e.g. 49.2% of the full sample and 7 1.4% of treatment responders in Simons et al., 1986) although there are some differences in the criteria used for treatment response and remission across the two studies. In contrast to our study, previous research that has found more powerful effects has typically employed an individual mode of administration or a combination of group and individual treatments (e.g. Covi and Lipman, 1987). A recently published study by Wierzbicki and Bartlett (1987) has also obtained reduced effects for cognitive therapy for depression in a group than in individual format, and a review of mean treatment effects by Nietzel, Russell, Hemmings and Gretter (1987) found that studies applying cognitive therapy in groups had a mean post-treatment BDI of 12.47. That figure is comparable to the present results and supports our contention that cognitive therapy was correctly administered within the constraints of the group format. Two possible reasons for the reduced impact that has been obtained in a group format may be the reduced time that is available to confront each individual’s cognitions and the reticence of some clients in revealing negative cognitions in front of other clients. Neither of these explanations suggest a different process by which individual and group therapy would operate, although our predictive analyses do need replication to ensure that they apply to individually administered cognitive therapy.

The variation in response to treatment did have one distinct advantage: it provided better opportunity to examine predictors and correlates of initial treatment outcome than when response is more homogeneous. Despite this opportunity, most of the predictor variables were not significantly related to initial treatment response. The result contrasted with data recently published by Hoberman, Lewinsohn and Tilson (1988) and with Simons et al. (1985). However, it supported the observation in Yusaf and Kavanagh (1989) that responses to cognitive-behavioural treatment for depression were poorly predicted by pretest measures. The depression model had made no predictions about the prior characteristics of responders, since initial skills or other features should be compensated by an appropriately designed treatment. The model’s focus on the process of


change and on the attainments of Ss at the end of treatment is borne out by the results of both Vusaf and Kavanagh (1989) and by the present study,

A next step in our research is to test whether self-efficacy on the CEQ has clinical utility as an indicator for treatment termination-i.e. whether relapse is reduced if therapists continue treatment until clients are confident about their ability to control negative cognitions in the months ahead, rather than stopping as soon as depression scores are lowered. We also want to replicate the prediction of Long-term outcomes with Ss who receive pharmacotherapy or other non-cognitive treatments, to see whether the results represent a general feature of recovery from depression or

a specific process variable within cognitive therapy. Hopefufly these data will help us to know more about prediction of outcome from depression treatment and the means by which therapists might improve this outcome.

Acknowfedgemenrs-We gratefuiiy acknowledge the assistance of Amanda Baker and Stehzi Yusaf (the primary therapists in the study) and of Dieter Schlosser and Deborah Knight, who conducted the additional treatment. Robyn Alexander, Mary Higson and Richard O’Kearney worked on assessment interviews, and Jennifer Cohen also assisted with administra~ve tasks and data entry. We thank Theresa Thomas for her work on the pre-test of our measures and Toni Zeiss for making the ICQ available to us. This research was supported by a Special Project Grant from the University of Sydney,

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